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7 Working with Laboratory Equipment 7.A INTRODUCTION 149 7.B WORKING WITH WATER-COOLED EQUIPMENT 149 7.C WORKING WITH ELECTRICALLY POWERED LABORATORY EQUIPMENT 149 7.C.1 General Principles 149 7.C.1.1 Outlet Receptacles 150 7.C.1.2 Wiring 150 7.C.1.3 General Precautions for Working with Electrical Equipment 151 7.C.1.4 Personal Safety Techniques for Use with Electrical Equipment 152 7.C.1.5 Additional Safety Techniques for Equipment Using High Current or High Voltage 152 7.C.2 Vacuum Pumps 153 7.C.3 Refrigerators and Freezers 153 7.C.4 Stirring and Mixing Devices 154 7.C.5 Heating Devices 154 7.C.5.1 Ovens 156 7.C.5.2 Hot Plates 157 7.C.5.3 Heating Mantles 157 7.C.5.4 Oil, Salt, or Sand Baths 158 7.C.5.5 Hot Air Baths and Tube Furnaces 158 7.C.5.6 Heat Guns 159 7.C.5.7 Microwave Ovens 159 7.C.6 Distillation 159 7.C.6.1 Solvent Stills 159 7.C.6.2 Column Purification Systems or “Push Stills” 160 7.C.7 Ultrasonicators, Centrifuges, and Other Electrical Equipment 161 7.C.7.1 Ultrasonicators 161 7.C.7.2 Centrifuges 161 7.C.7.3 Electrical Instruments 162 7.C.8 Electromagnetic Radiation Hazards 162 7.C.8.1 Visible, Ultraviolet, and Infrared Laser Light Sources 162 7.C.8.2 Radio-Frequency and Microwave Sources 162 7.C.8.3 X-Rays, Electron Beams, and Sealed Sources 162 7.C.8.4 Miscellaneous Physical Hazards Presented by Electrically Powered Equipment 164 7.D WORKING WITH COMPRESSED GASES 164 7.D.1 Compressed Gas Cylinders 164 7.D.1.1 Identification of Contents 165 7.D.2 Equipment Used with Compressed Gases 165 7.D.2.1 Records, Inspection, and Testing 165 7.D.2.2 Assembly and Operation 165 147
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148 PRUDENT PRACTICES IN THE LABORATORY 7.D.3 Handling and Use of Gas Cylinders 168 7.D.3.1 Preventing and Controlling Leaks 169 7.D.3.2 Pressure Regulators 169 7.D.3.3 Flammable Gases 170 7.E WORKING WITH HIGH OR LOW PRESSURES AND TEMPERATURES 170 7.E.1 Pressure Vessels 170 7.E.1.1 Records, Inspection, and Testing 170 7.E.1.2 Pressure Reactions in Glass Equipment 171 7.E.2 Liquefied Gases and Cryogenic Liquids 172 7.E.2.1 Cold Traps and Cold Baths 173 7.E.2.2 Selection of Low-Temperature Equipment 174 7.E.2.3 Cryogenic Lines and Supercritical Fluids 174 7.E.3 Vacuum Work and Apparatus 174 7.E.3.1 Glass Vessels 174 7.E.3.2 Dewar Flasks 174 7.E.3.3 Desiccators 175 7.E.3.4 Rotary Evaporators 175 7.E.3.5 Assembly of Vacuum Apparatus 175 7.F USING PERSONAL PROTECTIVE, SAFETY, AND EMERGENCY EQUIPMENT 175 7.F.1 Personal Protective Equipment and Apparel 175 7.F.1.1 Protective Clothing 175 7.F.1.2 Foot Protection 175 7.F.1.3 Eye and Face Protection 176 7.F.1.4 Hand Protection 176 7.F.2 Safety and Emergency Equipment 176 7.F.2.1 Spill Control Kits and Cleanup 177 7.F.2.2 Safety Shields 177 7.F.2.3 Fire Safety Equipment 177 7.F.2.4 Respiratory Protective Equipment 178 7.F.2.5 Safety Showers and Eyewash Units 180 7.F.2.6 Storage and Inspection of Emergency Equipment 180 7.G EMERGENCY PROCEDURES 181
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149 WORKING WITH LABORATORY EQUIPMENT 7.A INTRODUCTION without having to unclamp and reclamp secured lines. Some quick disconnects also incorporate check valves, Working safely with hazardous chemicals requires which do not allow flow into or out of either half of the proper use of laboratory equipment. Maintenance and connection when disconnected. This feature allows for regular inspection of laboratory equipment are essen- disconnecting and reconnecting with minimal spillage tial parts of this activity. Many of the accidents that oc- of water. To reduce the possibility of overpressurization cur in the laboratory can be attributed to improper use of fittings or glassware, consider installing a vented or maintenance of laboratory equipment. This chapter pressure relief device on the water supply. Interlocks discusses prudent practices for handling equipment are also available that shut off electrical power in the used frequently in laboratories. event of loss of coolant flow and are recommended for The most common equipment-related hazards in unattended operations. laboratories come from devices powered by electricity, devices for work with compressed gases, and devices for high or low pressures and temperatures. Other 7.C WORKING WITH ELECTRICALLY physical hazards include electromagnetic radiation POWERED LABORATORY EQUIPMENT from lasers and radio-frequency generating devices. Electrically powered equipment is used routinely for Seemingly ordinary hazards such as floods from water- laboratory operations requiring heating, cooling, agi- cooled equipment, accidents with rotating equipment tation or mixing, and pumping. Electrically powered and machines or tools for cutting and drilling, noise equipment found in the laboratory includes fluid and extremes, slips, trips, falls, lifting, and poor ergonom- vacuum pumps, lasers, power supplies, both electro- ics account for the greatest frequency of laboratory phoresis and electrochemical apparatus, x-ray equip- accidents and injuries. Understandably, injuries to the ment, stirrers, hot plates, heating mantles, microwave hands are very common in the laboratory. Care should ovens, and ultrasonicators. Attention must be paid to be taken to use appropriate gloves when handling labo- both the mechanical and the electrical hazards inherent ratory equipment to protect against electrical, thermal, in using these devices. High-voltage and high-power and chemical burns, cuts, and punctures. requirements are increasingly prevalent; therefore pru- dent practices for handling these devices are increas- 7.B WORKING WITH WATER- ingly necessary. COOLED EQUIPMENT Electric shock is the major electrical hazard. Although relatively low current of 10 mA poses some danger, 80 The use of water as a coolant in laboratory condens- to 100 mA can be fatal. In addition, if improperly used, ers and other equipment is common practice. Although electrical equipment can ignite flammable or explosive tap water is often used for these purposes, this practice vapors. Most of the risks can be minimized by regular should be discouraged. In many localities conserving proper maintenance and a clear understanding of the water is essential and makes tap water inappropri- correct use of the device. Before beginning any work, ate. In addition, the potential for a flood is greatly all personnel should be shown and trained in the use increased. Refrigerated recirculators can be expensive, of all electrical power sources and the location of emer- but are preferred for cooling laboratory equipment to gency shutoff switches. Information about emergency conserve water and to minimize the impact of floods. procedures can be found in section 7.G. To prevent freezing at the refrigeration coils, using a mixture of water and ethylene glycol as the coolant is prudent. Spills of this mixture are very slippery and 7.C.1 General Principles must be cleaned thoroughly to prevent slips and falls. Particular caution must be exercised during installa- Most flooding occurs when the tubing supplying the tion, modification, and repair, as well as during use of water to the condenser disconnects. Hoses can pop off the equipment. To ensure safe operation, all electrical when building water pressure fluctuates, causing ir- equipment must be installed and maintained in ac- regular flows, or can break when the hose material has cordance with the provisions of the National Electrical deteriorated from long-term or improper use. Floods Code (NEC) of the National Fire Protection Association also result when exit hoses jump out of the sink from a (NFPA, 2008). Trained laboratory personnel should also strong flow pulse or sink drains are blocked by an ac- consult state and local codes and regulations, which cumulation of extraneous material. Proper use of hose may contain special provisions and be more stringent clamps and maintenance of the entire cooling system than the NEC rules. All repair and calibration work on or alternative use of a portable cooling bath with suc- electrical equipment must be carried out by properly tion feed can resolve such problems. Plastic locking trained and qualified personnel. Before modification, disconnects can make it easy to unfasten water lines installation, or even minor repairs of electrical equip-
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150 PRUDENT PRACTICES IN THE LABORATORY ment are carried out, the devices must be deenergized and all capacitors discharged safely. Furthermore, this deenergized and/or discharged condition must be verified before proceeding. Note that the Occupational Safety and Health Administration (OSHA) Control of Hazardous Energy Standard (29 CFR § 1910.147, Lock out/Tag out) applies. All new electrical equipment should be inspected on receipt for a certification mark. If the device bears a certification mark from UL (Underwriters Laborato- ries Inc.), CSA (Canadian Standards Association), ETL F IGURE 7.1 R epresentative design for a three-wire (originally a mark of ETL Testing Laboratories, now a grounded outlet. The design shown is for 15-A, 125-V service. The specific design will vary with amperage and voltage. mark of Intertek Testing Services), or CE (Conformance European–Communaut Europenne or Conformit Europenne), detailed testing and inspection are not required. If the device does not bear one of these cer- situations. Certain types of GFCIs cause equipment tification marks, the device should be inspected by an shutdowns at unexpected and inappropriate times; electrician before it is put into service. hence, their selection and use need careful planning. Each person participating in any experiment involv- Be aware that GFCIs are not fail-safe devices. They ing the use of electrical equipment must be aware of significantly reduce the possibility of fatal shock but all applicable equipment safety issues and be briefed do not entirely eliminate it. on any potential problems. Trained laboratory person- Locate receptacles that provide electric power for nel can significantly reduce hazards and dangerous operations in laboratory chemical hoods outside the behavior by following some basic principles and hood. This location prevents the production of electri- techniques: checking and rechecking outlet recep- cal sparks inside the chemical hood when a device is tacles (section 7.C.1.1), making certain that wiring plugged in or disconnected, and it also allows trained complies with national standards and recommenda- laboratory personnel to disconnect electrical devices tions (section 7.C.1.2), reviewing general precautions from outside the hood in case of an accident. Cords (section 7.C.1.3) and personal safety techniques (sec- should not be routed in such a way that they can ac- tion 7.C.1.4), and ensuring familiarity with emergency cidentally be pulled out of their receptacles or tripped procedures (section 7.G). over. Simple inexpensive plastic retaining strips and ties can be used to route cords safely. For laboratory chemi- 7.C.1.1 Outlet Receptacles cal hoods with airfoils, route the electrical cords under All 110-V outlet receptacles in laboratories should be the bottom airfoil so that the sash can be closed com- of the standard design that accepts a three-prong plug pletely. Most airfoils are easily removed and replaced and provides a ground connection. Replace two-prong with a screwdriver. receptacles as soon as feasible, and add a separate ground wire so that each receptacle is wired as shown 7.C.1.2 Wiring in Figure 7.1.1 The ground wire is preferably (but not required by code) on top to prevent anything falling Fit laboratory equipment plugged into a 110-V (or onto a plug with exposed prongs, and will contact the higher) receptacle with a standard three-conductor line ground before contacting the hot or the neutral line. cord that provides an independent ground connection It is also possible to fit a receptacle with a ground- to the chassis of the apparatus (see Figure 7.2). Ground fault circuit interrupter (GFCI), which disconnects the all electrical equipment unless it is double-insulated. current if a ground fault is detected. GFCI devices are This type of equipment has a two-conductor line cord required by local electrical codes for outdoor recep- that meets national codes and standards. The use of tacles and for selected laboratory receptacles located two-pronged cheaters to connect equipment with less than 6 ft (1.83 m) from sinks if maintenance of a three-prong grounded plugs to old-fashioned two-wire good ground connection is essential for safe operation. outlets is hazardous and should be prohibited. These devices differ in operation and purpose from Limit the use of extension cords to temporary (<1 fuses and circuit breakers, which are designed primar- day) setups, if they are permitted at all. Use a standard ily to protect equipment and prevent electrical fires due three-conductor extension cord of sufficient rating for to short circuits or other abnormally high current draw the connected equipment with an independent ground connection. In addition, good practice uses only ex- 1The outlet is always “female”; the plug is always “male.” tension cords equipped with a GFCI. Install electrical
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151 WORKING WITH LABORATORY EQUIPMENT Three-Wire Receptacle Hot Wire 110 Volts to Ground (Black) Neutral Wire 0 Volts to Ground (White) Ground Wire 0 Volts to Ground (Green) Standard wiring convention for 110-V electric power to equipment. FIGURE 7.2 Figure 7.2.eps cables properly, even if only for temporary use, and mind that rubber-covered cords can be eroded by keep them out of aisles and other traffic areas. Install organic solvents, ozone (produced by ultraviolet overhead racks and floor channel covers if wires must lamps), and long-term air oxidation. pass over or under walking areas. Do not intermingle • Properly replace all frayed or damaged cords signal and power cables in cable trays or panels. Special before any further use of the equipment is per- care is needed when installing and placing water lines mitted. Qualified personnel should conduct the (used, for example, to cool equipment such as flash replacement. lamps for lasers) so that they do not leak or produce • Ensure the complete electrical isolation of electri- condensation, which can dampen power cables nearby. cal equipment and power supplies. Enclose all Equipment plugged into an electrical receptacle power supplies in a manner that makes accidental should include a fuse or other overload protection contact with power circuits impossible. In every device to disconnect the circuit if the apparatus fails or experimental setup, including temporary ones, is overloaded. This overload protection is particularly use suitable barriers or enclosures to protect useful for equipment likely to be left on and unattended against accidental contact with electrical circuits. for a long time, such as variable autotransformers (e.g., • Many laboratory locations are classified under fire Variacs and powerstats), 2 v acuum pumps, drying and electrical codes with a mandate for nonspark- ovens, stirring motors, and electronic instruments. If ing explosion-proof motors and electrical equip- equipment does not contain its own built-in overload ment. Areas where large amounts of flammable protection, modify it to provide such protection or re- solvents are in use also require explosion-proof place it with equipment that does. Overload protection lighting and electrical fixtures. The owners of does not protect the trained laboratory personnel from such facilities are responsible for ensuring that all electrocution but does reduce the risk of fire. electrical equipment and fixtures meet these codes and regulations. • Equip motor-driven electrical equipment used in 7.C.1.3 General Precautions for Working with a laboratory where volatile flammable materials Electrical Equipment may be present with either nonsparking induction Laboratory personnel should be certain that all elec- motors that meet Class 1, Division 2, Group C-D trical equipment is well maintained, properly located, electrical standards (Earley, 2008; NFPA, 2008) or and safely used. To do this, review the following pre- air motors instead of series-wound motors that cautions and make the necessary adjustments prior to use carbon brushes, such as those generally used working in the laboratory: in vacuum pumps, mechanical shakers, stirring motors, magnetic stirrers, and rotary evaporators. • Insulate all electrical equipment properly. Visually Do not use variable autotransformers to control inspect all electrical cords monthly, especially in the speed of an induction motor. The speed of any laboratory where flooding can occur. Keep in an induction motor is determined by the AC fre- quency rather than the voltage. Thus, using a vari- able autotransformer that controls voltage and not 2Commonly known as “variacs,” variable autotransformers are frequency could cause the motor to overheat and devices that provide a voltage-adjustable output of AC electricity presents a fire hazard. using a constant voltage input (e.g., the wall outlet).
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152 PRUDENT PRACTICES IN THE LABORATORY • Because series-wound motors cannot be modified and have in place, alternative power shutoffs (i.e., to make them spark-free, do not use appliances properly installed crash buttons, ready access to (e.g., kitchen refrigerators, mixers, and blenders) equipment power cord plugs). with such motors in laboratories where flammable • After making modifications to an electrical system materials may be present. or after a piece of equipment has failed, do not • When bringing ordinary electrical equipment use it again until it has been cleaned and properly such as vacuum cleaners and portable electric inspected. drills having series-wound motors into the labora- tory for special purposes, take specific precautions All laboratories should have access to a qualified to ensure that no flammable vapors are present technician who can make routine repairs to exist- before such equipment is used (see Chapter 6, ing equipment and modifications to new or existing section 6.G). equipment so that it will meet acceptable standards • Locate electrical equipment to minimize the pos- for electrical safety. The NFPA National Electrical Code sibility of spills onto the equipment or flammable Handbook (NFPA, 2008) provides guidelines. vapors carried into it. If water or any chemical is spilled on electrical equipment, shut off the power 7.C.1.4 Personal Safety Techniques for Use with immediately at a main switch or circuit breaker Electrical Equipment and unplug the apparatus using insulated rubber gloves. When operating or servicing electrical equipment, be • Minimize condensation that may enter electrical sure to follow basic safety precautions as summarized equipment if it is placed in a cold room or a large below. refrigerator. Cold rooms pose a particular risk in this respect because the atmosphere is frequently • Inform each individual working with electrical at a high relative humidity, and the potential for equipment of basic precautionary steps to take to water condensation is significant. ensure personal safety. • If electrical equipment must be placed in such • Avoid contact with energized electrical circuits. areas, mount the equipment on a wall or verti- Let only qualified individuals service electrical cal panel. This precaution reduces, but does not equipment. eliminate, the effects of condensation. • Before qualified individuals service electrical • Condensation can also cause electrical equipment equipment in any way, disconnect the power to overheat, smoke, or catch fire. In such a case, source to avoid the danger of electric shock. En- shut off the power to the equipment immediately sure that any capacitors are, in fact, discharged. at a main switch or circuit breaker and unplug the • Before reconnecting electrical equipment to its apparatus using insulated rubber gloves. power source after servicing, check the equip- • To minimize the possibility of electrical shock, ment with a suitable tester, such as a multimeter, carefully ground the equipment using a suitable to ensure that it is properly grounded. flooring material, and install GFCIs. • Do not reenergize a circuit breaker until sure that • Always unplug equipment before undertaking the cause of the short circuit has been corrected. any adjustments, modifications, or repairs (with • Install GCFIs as required by code to protect users the exception of certain instrument adjustments from electric shock, particularly if an electrical as indicated in section 7.C.7). When it is necessary device is handheld during a laboratory operation. to handle equipment that is plugged in, be certain • If a person is in contact with a live electrical hands are dry and, if feasible, wear nonconductive conductor, disconnect the power source before gloves and shoes with insulated soles. removing the person from the contact and admin- • Ensure that all laboratory personnel know the lo- istering first aid. cation and operation of power shutoffs (i.e., main switches and circuit breaker boxes) for areas in 7.C.1.5 Additional Safety Techniques for which they work. Voltages in breaker boxes may Equipment Using High Current or present an arc or flash hazard. Only qualified High Voltage personnel wearing proper personal protective equipment (PPE) are allowed to open these boxes Unless laboratory personnel are specially trained to to access the main switches and circuit breakers install or repair high-current or high-voltage equip- contained therein. Label high-voltage breaker ment, reserve such tasks for trained electrical workers. boxes presenting an arc or flash hazard. Trained The following reminders are included for qualified laboratory personnel should be familiar with, personnel:
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153 WORKING WITH LABORATORY EQUIPMENT • Always assume that a voltage potential exists rosive substances. General-purpose laboratory vacuum within a device while servicing it, even if it is pumps should have a record of use to prevent cross- deenergized and disconnected from its power contamination or reactive chemical incompatibility source. A device may contain capacitors, for problems. example, and could retain a potentially harmful Belt-driven mechanical pumps must have protective electrical charge. guards. Such guards are particularly important for • Work with only one hand, if it is not awkward pumps installed on portable carts or tops of benches or otherwise unsafe to do so, while keeping the where laboratory personnel might accidentally en- other hand at your side or in a pocket away from tangle clothing or fingers in the moving belt or wheels. all conducting materials. This precaution reduces Glassware under vacuum is at risk for implosion, the likelihood of accidents that result in current which could result in flying glass. (For more informa- passing through the chest cavity. tion about working under vacuum, see Chapter 4, • Avoid becoming grounded by staying at least 6 in. section 4.E.4.) away from walls, water, and all metal materials including pipes. 7.C.3 Refrigerators and Freezers • Use voltmeters and test equipment with ratings and leads sufficient to measure the highest po- The potential hazards posed by laboratory refrigera- tential voltage to be found inside the equipment tors include release of vapors from the contents, the being serviced. possible presence of incompatible chemicals, and spill- age. As general precautions, laboratory refrigerators should be placed against fire-resistant walls, should 7.C.2 Vacuum Pumps have heavy-duty power cords, and preferably should The use of water aspirators is discouraged. Their be protected by their own circuit breaker. Enclose the use in filtration or solvent-removal operations involv- contents of a laboratory refrigerator in unbreakable ing volatile organic solvents presents a hazard that secondary containment. Because there is almost never volatile chemicals will contaminate the wastewater a satisfactory way to continuously vent the interior and the sewer, even if traps are in place. Water and atmosphere of a refrigerator, any vapors escaping sewer contamination may result in violation of local, from vessels placed in one will accumulate in the re- state, or federal law. These devices also consume large frigerated space and gradually be absorbed into the volumes of water, present a flooding hazard, and can surrounding insulation. Thus, the atmosphere in a re- compromise local conservation measures. frigerator could contain an explosive mixture of air and Distillation or similar operations requiring a vacuum the vapor of a flammable substance or a dangerously must use a trapping device to protect the vacuum high concentration of the vapor of a toxic substance or source, personnel, and the environment. This require- both. The impact of exposure to toxic substances can ment also applies to oil-free Teflon-lined diaphragm be aggravated when a person inserts his or her head pumps. Normally the vacuum source is a cold trap inside a refrigerator to search for a particular sample. cooled with dry ice or liquid nitrogen. Even with the Placing potentially explosive (see Chapter 6, sections use of a trap, the oil in a mechanical vacuum trap can 6.C and 6.G) or highly toxic substances (see Chapter become contaminated and the waste oil must be treated 6, sections 6.D and 6.E) in a laboratory refrigerator is as a hazardous waste. strongly discouraged. As noted in Chapter 6, section Vent the output of each pump to a proper air exhaust 6.C, laboratory refrigerators are never used to store system. This procedure is essential when the pump is food or beverages for human consumption. Add per- being used to evacuate a system containing a volatile manent labels warning against the storage of food and toxic or corrosive substance. Failure to observe this pre- beverages to all laboratory refrigerators and freezers. caution results in pumping the untrapped substances Potential ignition sources, (e.g., electrical sparks) into the laboratory atmosphere. Scrubbing or absorb- must be eliminated from the inside of laboratory ing the gases exiting the pump is also recommended. refrigerators used to store flammable chemicals. Use Even with these precautions, volatile toxic or corrosive explosion-proof refrigerators for the storage of flam- substances may accumulate in the pump oil and thus mable materials; they are sold for this purpose and be discharged into the laboratory atmosphere during are labeled and hardwired. Only refrigerators that future pump use. Avoid this hazard by draining and have been UL- or FM (Factory Mutual)-approved for replacing the pump oil when it becomes contaminated. flammable storage should be used for this purpose. Follow procedures recommended by the institution’s A labeled hardwired explosion-proof refrigerator is environmental health and safety office for the safe mandatory for a renovated or new laboratory where disposal of pump oil contaminated with toxic or cor- flammable materials need refrigeration. Because of the
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154 PRUDENT PRACTICES IN THE LABORATORY expense of an explosion-proof refrigerator, a modified for flammable vapors. Consider the use of air-driven sparkproof refrigerator is sometimes found in older stirrers and other spark-free devices. Furthermore, it laboratories and laboratories using very small amounts is important that, in the event of an emergency, such of flammable materials. However, a modified spark- devices can be turned on or off from outside the labo- proof refrigerator cannot meet the standards of an ratory chemical hood. Heating baths associated with explosion-proof refrigerator. Where they exist, a plan these devices (e.g., baths for rotary evaporators) should to phase them out is recommended. also be spark-free and controllable from outside the Sparkproof refrigerators must have had the follow- hood. (See sections 7.C.1 and 7.C.5.) ing modifications: Use only spark-free induction motors in power stir- ring and mixing devices or any other rotating equip- • Interior light and switch mounted on the door ment used for laboratory operations. In some cases frame, if present, have been removed. these devices may be required by fire and electrical • Contacts of the thermostat controlling the fan and codes. Although the motors in most of the currently temperature have been moved outside the refrig- marketed stirring and mixing devices meet this cri- erated compartment. terion, their on/off switches and rheostat-type speed controls can produce an electrical spark any time they Permanently attach a prominent sign warning are adjusted, because they have exposed contacts. against the storage of flammable substances to the door Many of the magnetic stirrers and rotary evaporators of an unmodified refrigerator. Frost-free refrigerators currently on the market have this disadvantage. An ef- are not suitable for laboratory use, owing to the prob- fective solution is to remove any switch located on the lems associated with attempts to modify them. Many device and insert a switch in the cord near the plug end; of these refrigerators have a drain tube or hole that because the electrical receptacle for the plug should be carries water (and any flammable material present) to outside the chemical hood, this modification ensures an area adjacent to the compressor and thus present a that the switch will also be outside. Do not control the spark hazard. The electric heaters used to defrost the speed of an induction motor operating under a load by freezing coils are also a potential spark hazard (see sec- a variable autotransformer. tion 7.C.5). To ensure its effective functioning, defrost Because stirring and mixing devices, especially stir- a freezer manually when ice builds up. ring motors and magnetic stirrers, are often operated Never place uncapped containers of chemicals in a for fairly long periods without constant attention, refrigerator. Caps provide a vapor-tight seal to prevent consider the consequences of stirrer failure, electrical a spill if the container is tipped over. Aluminum foil, overload, or blockage of the motion of the stirring im- corks, corks wrapped with aluminum foil, and glass peller. In good practice a stirring impeller is attached to stoppers do not meet this criterion, and their use is the shaft of the stirring motor with lightweight rubber discouraged. The most satisfactory temporary seals tubing. If the motion of the impeller is impeded, the are normally screw caps lined with either a conical rubber can twist away from the motor shaft, and the polyethylene or a Teflon insert. The best containers motor will not stall. Because this practice does not al- for samples that are to be stored for longer periods of ways prevent binding of the impeller, it is also desirable time are sealed nitrogen-filled glass ampoules. At a to fit unattended stirring motors with a suitable fuse or minimum, use catch pans for secondary containment. thermal protection device. (Also see section 7.C.1.) Take Careful labeling of samples placed in refrigerators care when attaching an impeller shaft to an overhead and freezers with both the contents and the owner’s motor. If the attachment fails, the impeller shaft could name is essential. Do not use water-soluble ink; labels fall through the bottom of a glass vessel below, risking should be waterproof or covered with transparent tape. flying glass and a spill. Storing samples with due consideration of chemical compatibility is important in these often small crowded 7.C.5 Heating Devices spaces. Perhaps the most common types of electrical equip- ment found in a laboratory are the devices used to 7.C.4 Stirring and Mixing Devices supply the heat needed to effect a reaction or separa- The stirring and mixing devices commonly found in tion. These include ovens, hot plates, heating mantles laboratories include stirring motors, magnetic stirrers, and tapes, oil baths, salt baths, sand baths, air baths, shakers, small pumps for fluids, and rotary evapora- hot-tube furnaces, hot-air guns, and microwave ovens. tors for solvent removal. These devices are often used The use of steam-heated devices rather than electrically in laboratory chemical hoods, and they must be oper- heated devices is generally preferred whenever tem- ated such that they do not provide an ignition source peratures of 100 °C or less are required. Because they
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155 WORKING WITH LABORATORY EQUIPMENT do not present shock or spark risks, they can be left oil baths should not contain bare wires. If any heating unattended with assurance that their temperature will device becomes so worn or damaged that its heating never exceed 100 °C. Use steam that is generated by element is exposed, either discard the device or repair units that are dedicated to laboratory use. Steam gener- it before it is used again. ated for general facility use may contain contaminants Use laboratory heating devices with a variable au- that could interfere with laboratory work. totransformer to control and limit the input voltage to Take a number of general precautions when work- some fraction of the total line voltage, typically 110 V. If ing with heating devices in the laboratory. If using a a variable autotransformer is not wired in this manner, variable autotransformer (variac), be sure to wire (or the switch on it may or may not disconnect both wires rewire) new or existing equipment, as illustrated in Fig- of the output from the 110-V line when it is switched to ure 7.3, before use. However, temperature controllers the off position. Also, if this wiring scheme has not been with built-in safety interlock capability are available followed, and especially if the grounded three-prong from commercial sources and are preferred to variable plug is not used, even when the potential difference autotransformers. Enclose the actual heating element between the two output lines is only 10 V, each output in any laboratory heating device in a glass, ceramic, or line may be at a relatively high voltage (e.g., 110 V and insulated metal case to prevent a metallic conductor 100 V) with respect to an electrical ground. Because these or laboratory personnel from accidentally touching potential hazards exist, whenever laboratory personnel use a the wire carrying the electric current. This type of con- variable autotransformer with an unknown wiring scheme, struction minimizes the risk of electric shock and of prudent practice assumes that either of the output lines car- accidentally producing an electrical spark near a flam- ries a potential of 110 V and is capable of delivering a lethal mable liquid or vapor (see Chapter 6, section 6.G.1). It electric shock. also diminishes the possibility that a flammable liquid The external cases of all variable autotransformers or vapor will come into contact with wires at tem- have perforations for cooling and ventilation, and some peratures that might exceed its ignition temperature. sparking may occur whenever the voltage adjustment Because many household appliances (e.g., hot plates knob is turned. Therefore, locate these devices where and space heaters) do not meet this criterion, do not use water and other chemicals cannot be spilled onto them them in a laboratory. Resistance devices used to heat and where their movable contacts will not be exposed Output Receptacle Input Plug Double-Pole Switch Hot Wire Fuse Hot Wire Neutral Wire Neutral Wire Ground Wire Ground Wire Schematic diagram of a properly wired igure 7.3.eps Fvariable autotransformer. FIGURE 7.3
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156 PRUDENT PRACTICES IN THE LABORATORY to flammable liquids or vapors. Mount variable auto- VIGNETTE 7.1 transformers on walls or vertical panels and outside Oil bath fire as a result of a laboratory chemical hoods; do not simply place them loose temperature sensor on laboratory benchtops. Electrical input lines, including lines from variable A researcher walking past a laboratory no- transformers, to almost all laboratory heating devices ticed a flame burning behind the closed sashes have a potential of 110 V with respect to any electrical of the chemical fume hood. He determined that ground; always view these lines as potential shock and the oil in an oil bath was burning. There was no spark hazards. Connections from these lines to a heat- other equipment in the oil bath and no other ing device should be both mechanically and electrically chemicals were in the vicinity. The researcher secure and completely covered with insulating mate- turned off electrical service to the chemical fume rial. Do not use alligator clips to connect a line cord hood using the red Crash button on the front from a variable autotransformer to a heating device, and deemed it safe to attempt to extinguish the especially to an oil bath or an air bath, because such fire with a B/C extinguisher. When the sash was connections pose a shock hazard. They also may slip opened slightly to extinguish the fire, the flames off, creating an electrical spark and, perhaps, contact- flared through the opening and singed the re- ing other metal parts to create an additional hazard. searcher’s forehead and right forearm. The fire Make all connections by using, preferably, a plug- was extinguished immediately but continued to and-receptacle combination, or wires with insulated flare up because the oil was still above its autoig- terminals firmly secured to insulated binding posts. nition temperature. A metal pan was placed over Whenever an electrical heating device is used, either the oil bath to smother the fire. a temperature controller or a temperature-sensing de- An investigation determined that the ther- vice must be used that will turn off the electric power mocouple used by the oil bath temperature if the temperature of the heating device exceeds some controller had fallen out of the oil bath. The con- preset limit. Similar control devices are available that troller, responding to the false temperature drop will turn off the electric power if the flow of cooling reading, continued to supply power to the bath, water through a condenser is stopped owing to the loss resulting in overheating and fire. of water pressure or loosening of the water supply hose to a condenser. Independent temperature sensors must be used for the temperature controller and shutoff de- vices. Fail-safe devices, which can be either purchased 7.C.5.1 Ovens or fabricated, can prevent the more serious problems of fires or explosions that may arise if the temperature of Electrically heated ovens are commonly used in the a reaction increases significantly because of a change in laboratory to remove water or other solvents from line voltage, the accidental loss of reaction solvent, or chemical samples and to dry laboratory glassware. loss of cooling. Use fail-safe devices for stills purifying Never use laboratory ovens to prepare food for human reaction solvents, because such stills are often left un- consumption. attended for significant periods of time. Temperature- Purchase or construct laboratory ovens with their sensing devices absolutely must be securely clamped heating elements and their temperature controls physi- or firmly fixed in place, maintaining contact with the cally separated from their interior atmospheres. Small object or medium being heated at all times. If the household ovens and similar heating devices usually temperature sensor for the controller is not properly do not meet these requirements and, consequently, located or has fallen out of place, the controller will should not be used in laboratories. With the excep- continue to supply power until the sensor reaches the tion of vacuum drying ovens, laboratory ovens rarely temperature setting, creating an extremely hazardous prevent the discharge of the substances volatilized in situation. (See also Vignette 7.1.) them into the laboratory atmosphere. The volatilized Hot plates, oil baths, and heating mantles that can substances may also be present in sufficient concen- melt and combust plastic materials (e.g., vials, contain- tration to form explosive mixtures with the air inside ers, tubing) can cause laboratory fires, and the area the oven (see Chapter 6, section 6.G). This hazard can around the equipment should be cleared of those haz- be reduced by connecting the oven vent directly to an ards prior to use. Be aware that dry and concentrated exhaust system. (See Vignette 7.2.) residues can ignite when overheated in stills, ovens, Do not use ovens to dry any chemical sample that dryers, and other heating devices. has even moderate volatility and might pose a hazard (See section 7.C.1 for additional information.)
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157 WORKING WITH LABORATORY EQUIPMENT because of acute or chronic toxicity unless special pre- 7.C.5.2 Hot Plates cautions have been taken to ensure continuous venting Laboratory hot plates are often used when solutions of the atmosphere inside the oven. (See Vignette 7.2.) are to be heated to 100 °C or higher and the inherently Thus, do not dry most organic compounds in a conven- safer steam baths cannot be used as the source of heat. tional unvented laboratory oven. As previously noted, use only hot plates that have com- To avoid explosion, do not dry glassware that has pletely enclosed heating elements in laboratories. Al- been rinsed with an organic solvent in an oven until it though almost all laboratory hot plates currently sold has been rinsed again with distilled water. Potentially meet this criterion, many older ones pose an electrical explosive mixtures can be formed from volatile sub- spark hazard arising from either the on/off switch lo- stances and the air inside an oven. cated on the hot plate, the bimetallic thermostat used to Bimetallic strip thermometers are preferred for regulate the temperature, or both. Normally, these two monitoring oven temperatures. Do not mount mercury spark sources are located in the lower part of the hot thermometers through holes in the tops of ovens with plate in a region where any heavier-than-air and pos- the bulb hanging into the oven. If a mercury thermom- sibly flammable vapors evolving from a boiling liquid eter is broken in an oven of any type, close the oven on the hot plate would tend to accumulate. In principle, and turn it off immediately to avoid mercury exposure. these spark hazards are alleviated by enclosing all Keep it closed until cool. Remove all mercury from the mechanical contacts in a sealed container or by using cold oven with the use of appropriate cleaning equip- solid-state circuitry for switching and temperature ment and procedures (see Chapter 6, section 6.C.10.8). control. However, in practice, such modifications are After removal of all visible mercury, monitor the heated difficult to incorporate into many of the hot plates now oven in a laboratory chemical hood until the mercury in use. Warn laboratory personnel of the spark hazard vapor concentration drops below the threshold limit associated with these hot plates. Set up any newly value. (For information about reducing the use of purchased hot plates to avoid electrical sparks. In ad- mercury in thermometers, see Chapter 5, section 5.B.8.) dition to the spark hazard, old and corroded bimetallic thermostats in these devices can eventually fuse shut and deliver full continuous current to a hot plate. This risk can be avoided by wiring a fusible coupling into the line inside the hot plate. If the device does overheat, the coupling will melt and interrupt the current (see section 7.C.1). On many brands of combined stirrer/hot plates, the VIGNETTE 7.2 controls for the stirrer and temperature control are not Muffle furnace fire easily differentiated. Care must be taken to distinguish A laboratory specializing in the analysis of their functions. A fire or explosion may occur if the paint samples was asked to analyze pigmented temperature rather than the stirrer speed is increased polypropylene. The first step of the analytical inadvertently. protocol called for ashing the sample in a muffle furnace. The technician loaded the furnace with 7.C.5.3 Heating Mantles four crucibles containing a total of approximately 110 g of polypropylene. The temperature was set Heating mantles are commonly used to heat round- to ramp up to 900 °C. At approximately 500 °C a bottom flasks, reaction kettles, and related reaction ves- fire erupted from the furnace, which was quickly sels. These mantles enclose a heating element in layers extinguished. of fiberglass cloth. As long as the fiberglass coating is Two major contributing factors to the fire were not worn or broken and no water or other chemicals identified. First, the technician had no experience are spilled into the mantle (see section 7.C.1), heating with the analysis of polypropylene-containing mantles pose minimal shock hazard. They are normally samples and did not recognize that polypropyl- fitted with a male plug that fits into a female receptacle ene begins to decompose at approximately 500 on an output line from a variable autotransformer. This °C to low-molecular-weight olefins. Second, the plug combination provides a mechanically and electri- amount of organic matter placed in the furnace cally secure connection. in the form of the polypropylene samples was Always use heating mantles with a variable auto- significantly more than that in the usual paint transformer to control the input voltage. Never plug samples. them directly into a 110-V line. Trained laboratory personnel should be careful not to exceed the input
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172 PRUDENT PRACTICES IN THE LABORATORY 7.E.2 Liquefied Gases and Cryogenic or toxic reactants by using suitable shielding. Often a Liquids mesh is provided around the glassware to catch pieces should the vessel rupture. Seal centrifuge bottles with Cryogenic liquids are materials with boiling points rubber stoppers clamped in place, wrapped with fric- of less than −73 °C (−100 °F). Liquid nitrogen, helium, tion tape and shielded with a metal screen or wrapped argon, and slush mixtures of dry ice with isopropyl with friction tape and surrounded by multiple layers alcohol are the materials most commonly used in cold of loose cloth toweling, and clamped behind a good traps to condense volatile vapors from a gas or vapor safety shield. Some bottles are typically equipped with stream. In addition, oxygen, hydrogen, and helium are a head-containing inlet and exhaust gas valves, a pres- often used in the liquid state. sure gauge, and a pressure-relief valve. If a pressure The primary hazards of cryogenic liquids are frost- gauge is not used, estimate the maximum internal pres- bite, asphyxiation, fire or explosion, pressure buildup sure by calculation prior to beginning the experiment (either slowly or due to rapid conversion of the liquid to ensure that the maximum allowable pressure is not to the gaseous state), and embrittlement of structural exceeded. When corrosive materials are used, use a Tef- materials. The extreme cold of cryogenic liquids re- lon pressure-relief valve. The preferred source of heat quires special care in their use. The vapor that boils for such vessels is steam, because an explosion in the off from a liquid can cause the same problems as the vicinity of an electrical heater could start a fire and an liquid itself. explosion in a liquid heating bath would scatter hot liq- The fire or explosion hazard is obvious when gases uid around the area. Carry out any reaction of this type such as oxygen, hydrogen, methane, and acetylene are in a chemical hood, labeled with signs that indicate the used. Air enriched with oxygen can greatly increase contents of the reaction vessel and the explosion risk. the flammability of ordinary combustible materials Fill glass tubes under pressure no more than three- and may even cause some noncombustible materials to quarters full. Appropriate precautions using the proper burn readily (see Chapter 6, sections 6.G.4 and 6.G.5). shielding must be taken for condensing materials and Oxygen-saturated wood and asphalt have been known sealing tubes. Vacuum work can be carried out on a to explode when subjected to shock. Because oxygen Schlenk line, an apparatus used for work with air- has a higher boiling point (−183 °C) than nitrogen sensitive compounds, as long as proper technique is (−195 °C), helium (−269 °C), or hydrogen (−252.7 °C), used. The sealed glass tubes can be placed either inside it can be condensed out of the atmosphere during the pieces of brass or iron pipe capped at one end with use of these lower boiling-point cryogenic liquids. a pipe cap or in an autoclave containing some of the With the use of liquid hydrogen particularly, explosive reaction solvent (to equalize the pressure inside and conditions may develop. (See Chapter 6, sections 6.F.3 outside the glass tube). The tubes can be heated with and 6.G.2, for further discussion.) steam or in a specially constructed, electrically heated Furnish all cylinders and equipment containing sealed-tube furnace that is controlled thermostatically flammable or toxic liquefied gases (not vendor-owned) and located to direct the force of an explosion into a safe with a spring-loaded pressure-relief device (not a rup- area. When the required heating has been completed, ture disk) because of the magnitude of the potential allow the sealed tube or bottle to cool to room tem- risk that can result from activation of a nonresetting perature. Wrap sealed bottles and tubes of flammable relief device. Commercial cylinders of liquefied gases materials with cloth toweling, place behind a safety are normally supplied only with a fusible-plug type of shield, and cool slowly, first in an ice bath and then in relief device, as permitted by DOT regulations. Protect dry ice. After cooling, the clamps and rubber stoppers pressurized containers that contain cryogenic material can be removed from the bottles prior to opening. Use with multiple pressure-relief devices. PPE and apparel, including shields, masks, coats, and Cryogenic liquids must be stored, shipped, and han- gloves, during tube-opening operations. Note that dled in containers that are designed for the pressures NMR tubes are often thin-walled and should only be and temperatures to which they may be subjected. used for pressure reactions in a special high-pressure Materials that are pliable under normal conditions probe or in capillary devices. can become brittle at low temperatures. Dewar flasks, Examine newly fabricated or repaired glass equip- which are used for relatively small amounts of cryo- ment for flaws and strains under polarized light. Never genic material, should have a dust cap over the outlet rely on corks, rubber stoppers, and rubber or plastic to prevent atmospheric moisture from condensing and tubing as relief devices to protect glassware against plugging the neck of the tube. Special cylinders that excess pressure; use a liquid seal, Bunsen tube, or are insulated and vacuum-jacketed with pressure-relief equivalent positive-relief device. With glass pipe, use valves and rupture devices to protect the cylinder from only proper metal.
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173 WORKING WITH LABORATORY EQUIPMENT pressure buildup are available in capacities of 100 to are used for the storage and handling of liquefied gases 200 L. to more than 80% capacity, to protect against possible A special risk to personnel is skin or eye contact with thermal expansion of the contents and bursting of the the cryogenic liquid. Because these liquids are prone vessel by hydrostatic pressure. If the possibility ex- to splash owing to the large volume expansion ratio ists that the temperature outside of the cylinder may when the liquid warms up, wear eye protection, prefer- increase to greater than 30°C, a lower percentage (e.g., ably chemical splash goggles and a face shield, when 60%) of capacity should be the limit. handling liquefied gases and other cryogenic fluids. Do not transfer liquefied gases from one container to 7.E.2.1 Cold Traps and Cold Baths another for the first time without the direct supervision and instruction of someone who is experienced in this Choose cold traps that are large enough and cold operation. Transfer very slowly to minimize boiling enough to collect the condensable vapors. Check cold and splashing. traps frequently to make sure they do not become Do not allow unprotected parts of the body to plugged with frozen material. After completion of an come in contact with uninsulated vessels or pipes operation in which a cold trap has been used, isolate that contain cryogenic liquids because extremely cold the trap from the source, remove from the coolant, and material may bond firmly to the skin and tear flesh vent to atmospheric pressure in a safe and environmen- if separation or withdrawal is attempted. Even very tally acceptable way. Otherwise, pressure could build brief skin contact with a cryogenic liquid can cause up, creating a possible explosion or sucking pump oil tissue damage similar to that of frostbite or thermal into a vacuum system. Cold traps under continuous burns, and prolonged contact may result in blood use, such as those used to protect inert atmosphere clots that have potentially very serious consequences. dryboxes, should be electrically cooled, and their tem- Gloves must be insulated, impervious to the fluid be- perature should be monitored with low-temperature ing handled, and loose enough to be tossed off easily probes. in case the cryogenic liquid becomes trapped close to Use appropriate gloves and a face shield to avoid the skin. Never wear tight gloves when working with contact with the skin when using cold baths. Wear dry cryogenic liquids. Trained laboratory personnel are gloves when handling dry ice. Do not lower the head also encouraged to wear long sleeves when handling into a dry ice chest because carbon dioxide is heavier cryogenic fluids. Handle objects that are in contact with than air and asphyxiation can result. The preferred cryogenic liquids with tongs or potholders. Ventilate liquids for dry-ice cooling baths are isopropyl alcohol the work area well. Virtually all liquid gases present or glycols; add dry ice slowly to the liquid portion of the threat of poisoning, explosion, or, at a minimum, the cooling bath to avoid foaming. Avoid the common asphyxiation in a confined space. Major harmful con- practice of using acetone–dry ice as a coolant; the al- sequences of the use of cryogenic inert gases, including ternatives are less flammable, less prone to foaming asphyxiation, are due to boiling off of the liquid and and splattering with dry ice, and less likely to damage pressure buildup, which can lead to violent rupture of some trap components (O-rings, plastic). Dry ice and the container or piping. liquefied gases used in refrigerant baths should always Take special care when handling liquid hydrogen. be open to the atmosphere. Never use them in closed In general, do not transfer liquid hydrogen in an air systems, where they may develop uncontrolled and atmosphere because oxygen from the air can condense dangerously high pressures. in the liquid hydrogen, presenting a possible explosion Exercise extreme caution in using liquid nitrogen risk. Take all precautions to keep liquid oxygen from as a coolant for a cold trap. If such a system is opened organic materials; spills on oxidizable surfaces can be while the cooling bath is still in contact with the trap, hazardous. oxygen may condense from the atmosphere. The oxygen Although nitrogen is inert, its liquefied form can could then combine with any organic material in the be hazardous because of its cryogenic properties and trap to create a highly explosive mixture. Therefore, because displacement of air oxygen in the vicinity do not open a system that is connected to a liquid ni- can lead to asphyxiation followed by death with little trogen trap to the atmosphere until the liquid nitrogen warning. Fit rooms that contain appreciable quanti- Dewar flask or container has been removed. A liquid ties of liquid nitrogen (N2) with oxygen meters and nitrogen–cooled trap must never be left under static alarms. Do not store liquid nitrogen in a closed room vacuum. Also, if the system is closed after even a brief because the oxygen content of the room can drop to exposure to the atmosphere, some oxygen may have unsafe levels. already condensed. Then, when the liquid nitrogen Do not fill cylinders and other pressure vessels that bath is removed or when it evaporates, the condensed
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174 PRUDENT PRACTICES IN THE LABORATORY gases will vaporize, producing a pressure buildup and cause an implosion could scatter hot flammable liquid. the potential for explosion. The same explosion hazard Use an explosion shield and a full-face shield to protect can be created if liquid nitrogen is used to cool a flam- laboratory personnel, and carry the procedure out in mable mixture that is exposed to air. Caution must a laboratory chemical hood. Glassware under vacuum be applied when using argon, for instance as an inert should be kept behind a shield or hood sash, taped, or gas for Schlenk or vacuum lines, because it condenses resin (plastic) coated. as a colorless solid at liquid nitrogen temperature. A Equipment at reduced pressure is especially prone to trap containing frozen argon is indistinguishable from rapid pressure changes, which can create large pressure one containing condensed solvent or other volatiles differences within the apparatus. Such conditions can and presents an explosion hazard if allowed to warm push liquids into unwanted locations, sometimes with without venting. undesirable consequences. Do not allow water, solvents, and corrosive gases to be drawn into a building vacuum system. When the 7.E.2.2 Selection of Low-Temperature Equipment potential for such a problem exists, use a cold trap. Select equipment used at low temperatures carefully Water aspirators are not recommended. because temperature can dramatically change charac- Protect mechanical vacuum pumps by cold traps, teristics of materials. For example, the impact strength and vent their exhausts to an exhaust hood or to the of ordinary carbon steel is greatly reduced at low tem- outside of the building. If solvents or corrosive sub- peratures, and failure can occur at points of weakness, stances are inadvertently drawn into the pump, change such as notches or abrupt changes in the material of the oil before any further use. (Oil contaminated with construction. When combinations of materials are re- solvents, mercury, and corrosive substances must be quired, consider the temperature dependence of their handled as hazardous waste.) It may be desirable to volumes so that leaks, ruptures, and glass fractures maintain a log of pump usage as a guide to length of are avoided. For example, O-rings that provide a good use and potential contaminants in the pump oil. Cover seal at room temperature may lose resilience and fail the belts and pulleys on vacuum pumps with guards. to function on chilled equipment. (See section 7.C.2 for a discussion of vacuum Stainless steels containing 18% chromium and 8% pumps.) nickel retain their impact resistance down to approxi- mately −240 °C; the exact value depends heavily on 7.E.3.1 Glass Vessels special design considerations. The impact resistance of aluminum, copper, nickel, and many other nonferrous Although glass vessels are frequently used in low- metals and alloys increases with decreasing tempera- vacuum operations, evacuated glass vessels may col- tures. Use special alloy steels for liquids or gases con- lapse violently, either spontaneously from strain or taining hydrogen at temperatures greater than 200 °C from an accidental blow. Therefore, conduct pressure or at pressures greater than 34.5 MPa (500 psi) because and vacuum operations in glass vessels behind ad- of the danger of weakening carbon steel equipment by equate shielding. Check for flaws such as star cracks, hydrogen embrittlement. scratches, and etching marks each time a vacuum ap- paratus is used. These flaws can often be noticed if the vessel is help up to a light. Use only round-bottom or 7.E.2.3 Cryogenic Lines and Supercritical Fluids thick-walled (e.g., Pyrex) evacuated reaction vessels Design liquid cryogen transfer lines so that liquid specifically designed for operations at reduced pres- cannot be trapped in any nonvented part of the sys- sure. Do not use glass vessels with angled or squared tem. Experiments in supercritical fluids include high edges in vacuum applications unless specifically de- pressure and should be carried out with appropriate signed for the purpose (e.g., extra thick glass). Repaired protective systems. glassware must be properly annealed and inspected with a cross-polarizer before vacuum or thermal stress is applied. Never evacuate thin-walled, Erlenmeyer, or 7.E.3 Vacuum Work and Apparatus round-bottom flasks larger than 1 L. Vacuum work can result in an implosion and the possible hazards of flying glass, spattering chemicals, 7.E.3.2 Dewar Flasks and fire. Set up and operate all vacuum operations with careful consideration of the potential risks. Although Dewar flasks are under high vacuum and can col- a vacuum distillation apparatus may appear to pro- lapse as a result of thermal shock or a very slight me- vide some of its own protection in the form of heating chanical shock. Shield them, either by a layer of fiber- mantles and column insulation, this is not sufficient be- reinforced friction tape or by enclosure in a wooden or
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175 WORKING WITH LABORATORY EQUIPMENT 7.F USING PERSONAL metal container, to reduce the risk of flying glass in case PROTECTIVE, SAFETY, AND of collapse. Use metal Dewar flasks whenever there is EMERGENCY EQUIPMENT a possibility of breakage. Styrofoam buckets with lids can be a safer form of As outlined in previous chapters, trained labora- short-term storage and conveyance of cryogenic liq- tory personnel must be proactive to ensure that the uids than glass vacuum Dewar flasks. Although they laboratory is a safe working environment. This attitude do not insulate as well as Dewar flasks, they eliminate begins with wearing appropriate apparel and using the danger of implosion. proper eye, face, hand, and foot protection when work- ing with hazardous materials. The institution is respon- sible for providing appropriate safety and emergency 7.E.3.3 Desiccators equipment for laboratory personnel and emergency If a glass vacuum desiccator is used, it should be personnel. (See also section 6.C.) made of Pyrex or similar glass, completely enclosed in a shield or wrapped with friction tape in a grid pat- 7.F.1 Personal Protective Equipment and tern that leaves the contents visible and at the same Apparel time guards against flying glass if the vessel implodes. Plastic (e.g., polycarbonate) desiccators reduce the risk of implosion and may be preferable but should also 7.F.1.1 Protective Clothing be shielded while evacuated. Solid desiccants are pre- Clothing that leaves large areas of skin exposed is ferred. Never carry or move an evacuated desiccator. Take inappropriate in laboratories where hazardous chemi- care opening the valve to avoid spraying the desiccator cals are in use. Personal clothing should fully cover the contents from the sudden inrush of gas. body. Appropriate laboratory coats should be worn, buttoned, with the sleeves rolled down. Leave lab coats in the laboratory to minimize the possibility of spread- 7.E.3.4 Rotary Evaporators ing chemicals to public assembly, eating, or office areas, Glass components of the rotary evaporator should be and clean them regularly. [For more information, see made of Pyrex or similar glass. Completely enclose in a the OSHA Personal Protective Equipment Standard (29 shield to guard against flying glass should the compo- CFR § 1910.132) and the OSHA Laboratory Standard nents implode. Gradually increase rotation speed and (29 CFR § 1910.1450).] application of vacuum to the flask whose solvent is to Always wear protective apparel if there is a possibil- be evaporated. ity that personal clothing could become contaminated or damaged with chemically hazardous material. Washable or disposable clothing worn for laboratory 7.E.3.5 Assembly of Vacuum Apparatus work with especially hazardous chemicals includes Assemble vacuum apparatus to avoid strain. Joints special laboratory coats and aprons, jumpsuits, special must allow various sections of the apparatus to be boots, shoe covers, and gauntlets, as well as splash moved if necessary without transmitting strain to the suits. Protection from heat, moisture, cold, and radia- necks of the flasks. Support heavy apparatus from be- tion may be required in special situations. Among the low as well as by the neck. Protect vacuum and Schlenk factors to be considered in choosing protective apparel, lines from overpressurization with a bubbler. Gas in addition to the specific application, are resistance regulators and metal pressure-relief devices must not to physical hazards, flexibility and ease of movement, be relied on to protect vacuum and Schlenk lines from chemical and thermal resistance, and ease of cleaning overpressurization. If a slight positive pressure of gas or disposal. on these lines is desired, the recommended pressure (See also Chapter 6, section 6.C.2.6.2.) range is not in excess of 1 to 2 psi. This pressure range is easily obtained by proper bubbler design (depth of the exit tubing in the bubbler liquid). 7.F.1.2 Foot Protection Place vacuum apparatus well back onto the bench or Not all types of footwear are appropriate in a labora- into the laboratory chemical hood where it will not be tory where both chemical and mechanical hazards may inadvertently hit. If the back of the vacuum setup faces exist. Wear substantial shoes in areas where hazard- the open laboratory, protect it with panels of suitably ous chemicals are in use or mechanical work is being heavy transparent plastic to prevent injury to nearby done. Clogs, perforated shoes, sandals, and cloth shoes personnel from flying glass in case of implosion. do not provide protection against spilled chemicals. In many cases, safety shoes are advisable. Steel toes
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176 PRUDENT PRACTICES IN THE LABORATORY are recommended when working with heavy objects ardous chemicals. Wear proper protective gloves when such as gas cylinders. Shoe covers may be required for handling hazardous chemicals, toxic materials, materi- work with especially hazardous materials. Shoes with als of unknown toxicity, corrosive materials, rough or conductive soles prevent buildup of static charge, and sharp-edged objects, and very hot or very cold objects. insulated soles can protect against electrical shock. (See Chapter 6, section 6.C.2.6.1, for more information about selecting and using gloves to prevent chemical exposure.) The following list highlights some basic 7.F.1.3 Eye and Face Protection information regarding protection of hands. Appropriate eye protection is a requirement for working in a chemical laboratory. Requisite eye protec- • Before using gloves, inspect them for integrity and tion should be provided for laboratory personnel and check for discoloration, punctures, or tears. visitors, and signs should be posted outside the labo- • The thin latex surgical vinyl and nitrile gloves ratory indicating that eye protection is required where that are popular in many laboratories may not be hazardous chemicals are in use. Ordinary prescrip- appropriate for use with highly toxic chemicals tion glasses with hardened lenses do not serve as eye or solvents because of their composition and thin protection in the laboratory. Appropriate laboratory construction. • Cut-resistant gloves, such as Kevlar® or leather eye and face protection includes impact goggles with splash protection (chemical splash goggles), full-face gloves, are appropriate for handling broken glass- shields that also protect the throat, and specialized eye ware, inserting tubing into stoppers, and handling protection (i.e., protection against ultraviolet light or sharp-edged objects if protection from chemicals laser light). The following provides basic information is not needed. regarding eye protection. (For more information, see • Wear insulated gloves when working with very Chapter 6, section 6.C.2.2.) hot or very cold materials. With cryogenic fluids the gloves must be impervious to fluid but loose • Wear impact protection goggles if there is a dan- enough to be tossed off easily. Absorbent gloves ger of flying particles, and full-face shields with could freeze on the hand and intensify any expo- safety glasses and side shields for complete face sure to liquefied gases. and throat protection. • Wear insulating rubber gloves when working • Although safety glasses can provide satisfactory with electrical equipment. protection from flying particles, they do not fit • Wear a double set of gloves when a single glove tightly against the face and offer little protection material does not provide adequate protection for against splashes or sprays of chemicals. Chemical all the hazards encountered in a given operation. splash goggles that conform to ANSI standard For instance, operations involving a chemical Z87.1-2003 are recommended when working in hazard and sharp objects may require the com- laboratories and, in particular, when working bined use of a chemical-resistant glove and a cut- with hazardous chemicals that present a splash resistant glove. hazard, with vapors or particulates, and with • Replace gloves immediately if they are contami- corrosives. Chemical splash goggles have splash- nated or torn. proof sides to fully protect the eyes. • Replace gloves periodically, depending on the • When there is a possibility of liquid splashes, wear frequency of use. Regular inspection of their ser- both a face shield and chemical splash goggles; viceability is important. If they cannot be cleaned, this is especially important for work with highly dispose of contaminated gloves according to insti- corrosive liquids. tutional procedures. • Use full-face shields with throat protection and • Decontaminate or wash gloves appropriately be- safety glasses with side shields when handling fore removing them; leave gloves in the work area, explosive or highly hazardous chemicals. and do not touch any uncontaminated objects in • Wear specialized eye protection if work in the the laboratory or any other area. laboratory could involve exposure to lasers, ultra- violet light, infrared light, or intense visible light. 7.F.2 Safety and Emergency Equipment Safety equipment, including spill control kits, safety 7.F.1.4 Hand Protection shields, fire safety equipment, respirators, safety show- Use gloves that are appropriate to the degree and ers and eyewash units, and emergency equipment type of hazard. At all times pay special attention to the should be available in well-marked highly visible hands and any skin that is likely to be exposed to haz- locations in all chemical laboratories. Fire-alarm pull
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177 WORKING WITH LABORATORY EQUIPMENT stations and telephones with emergency contact num- limited severity, such as small splashes, heat, and fires. bers must be readily accessible. In addition to the stan- A portable shield, however, provides no protection at dard items, other safety devices may also be needed. the sides or back of the equipment, and if it is not suf- The laboratory supervisor is responsible for ensuring ficiently weighted for forward protection, the shield proper training and providing supplementary equip- may topple toward personnel during a blast. A fixed ment as needed. shield that completely surrounds the experimental apparatus can afford protection against minor blast damage. Polymethyl methacrylate, polycarbonate, 7.F.2.1 Spill Control Kits and Cleanup poly(vinyl chloride), and laminated safety plate glass All personnel who work in a laboratory in which are all satisfactory transparent shielding materials. hazardous substances are used should be familiar Where combustion is possible, the shielding mate- with their institution’s policy regarding spill control. rial should be nonflammable or slow burning; if it For non-emergency3 spills, spill control kits may be can withstand the working blast pressure, laminated available. Tailor them to deal with the potential risk safety plate glass may be the best material for such associated with the materials being used in the labora- circumstances. When cost, transparency, high-tensile tory. These kits are used to confine and limit the spill strength, resistance to bending loads, impact strength, if such actions can be taken without risk of injury or shatter resistance, and burning rate are considered, contamination. If a spill exceeds the on-scene person- poly(methyl methacrylate) offers an excellent overall nel’s ability or challenges their safety, they should leave combination of shielding characteristics. the spill site and call the emergency telephone number P o l y c a r b o n a t e i s m u c h s t ro n g e r a n d s e l f - for help. Emergency response spill cleanup personnel extinguishing after ignition but is readily attacked by should be provided with all available information organic solvents. about the spill. Specific procedures for cleaning up spills vary de- 7.F.2.3 Fire Safety Equipment pending on the location of the accident, the amount and physical properties of the spilled material, the de- 7.F.2.3.1 ire Extinguishers F gree and type of toxicity, and the training of the person- All chemical laboratories should have carbon diox- nel involved. A typical cleanup kit may be a container ide and dry chemical fire extinguishers. Other types on wheels that can be moved to the location of the spill of extinguishers should be available if required for and may include such items as instructions; absorbent the work that will be performed in the laboratory. The pads; a spill absorbent mixture for liquid spills; a poly- four types of most commonly used extinguishers are ethylene scoop for dispensing spill absorbent, mixing it listed below, classified by the type of fire for which they with the spill, and picking up the mixture; thick poly- are suitable. Note that multipurpose class A, B, and C ethylene bags for disposal of the mixture; and tags and extinguishers are available. ties for labeling the bags. Use any kit in conjunction with the appropriate PPE, and dispose of the material • Water extinguishers are effective against burning according to institutional requirements. paper and trash (Class A fires). Do not use them (Also see Chapter 6, section 6.C.10.5.) for electrical, liquid, or metal fires. • Carbon dioxide extinguishers are effective against burning liquids, such as hydrocarbons or paint, 7.F.2.2 Safety Shields and electrical fires (Class B and C fires). They are Use safety shields for protection against possible recommended for fires involving computer equip- explosions or splash hazards. Shield laboratory equip- ment, delicate instruments, and optical systems ment on all sides to avoid any line-of-sight exposure because they do not damage such equipment. of personnel. The front sashes of laboratory chemical CO2 extinguishers are less effective against paper hoods provide shielding. Use a portable shield also and trash fires and must not be used against metal when manipulations are performed, particularly with hydride or metal fires. Care must be taken in us- chemical hoods that have vertical-rising doors rather ing these extinguishers, because the force of the than horizontal-sliding sashes. compressed gas can spread burning combustibles Use portable shields to protect against hazards of such as papers and can tip over containers of flam- mable liquids. • Dry powder extinguishers, which contain am - 3A non-emergency response is appropriate in the case of an inci- monium phosphate or sodium bicarbonate, are dental release of hazardous substances where the substance can be effective against burning liquids and electrical absorbed, neutralized, or otherwise controlled at the time of release by personnel in the immediate area or by maintenance personnel. fires (Class B and C fires). They are less effective
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178 PRUDENT PRACTICES IN THE LABORATORY against paper and trash or metal fires and are not fires; instead, it can cause the fire to spread or float to recommended for fires involving delicate instru- adjacent areas. These possibilities are minimized by the ments or optical systems because of the cleanup use of a water fog. Water fogs are used extensively by problem. Computer equipment may need to be the petroleum industry because of their fire-controlling replaced if exposed to sufficient amounts of the and extinguishing properties. A fog can be used safely dry powders. These extinguishers are generally and effectively against fires that involve oil products, used where large quantities of solvent may be as well as those involving wood, rags, and rubbish. present. Because of the potential risks involved in using water • Met-L-X extinguishers and others that have spe- around chemicals, laboratory personnel should not use cial granular formulations are effective against fire hoses except in extreme emergencies. Reserve them burning metal (Class D fires). Included in this for trained firefighters. Extinguish clothing fires by im- category are fires involving magnesium, lithium, mediately dropping to the floor and rolling; however, if sodium, and potassium; alloys of reactive met- a safety shower is nearby, use it to extinguish a clothing als; and metal hydrides, metal alkyls, and other fire (as noted in section 7.F.2.5). organometallics. These extinguishers are less ef- 7.F.2.3.4 utomatic Fire-Extinguishing Systems A fective against paper and trash, liquid, or electrical fires. In areas where fire potential and the risk of injury or damage are high, automatic fire-extinguishing systems Every extinguisher should carry a label indicating are often used. These may be of the water sprinkler, what class or classes of fires it is effective against and foam, carbon dioxide, halon, or dry chemical type. If an the date it was last inspected. A number of other more automatic fire-extinguishing system is in place, inform specialized types of extinguishers are available for laboratory personnel of its presence and advise them of unusual fire hazard situations. All trained laboratory any safety precautions required in connection with its personnel are responsible for knowing the location, op- use (e.g., evacuation before a carbon dioxide total-flood eration, and limitations of the fire extinguishers in the system is activated, to avoid asphyxiation). work area. The laboratory supervisor is responsible for ensuring that all personnel are aware of the locations of 7.F.2.4 Respiratory Protective Equipment fire extinguishers and are trained in their use. After an extinguisher is used, designated personnel promptly The primary method for the protection of laboratory recharge or replace it. personnel from airborne contaminants is to minimize the amount of such materials entering the laboratory 7.F.2.3.2 eat Sensors and Smoke Detectors H air. When effective engineering controls are not pos- Heat sensors and smoke detectors may be part of sible, use suitable respiratory protection after proper the building safety equipment. If designed into the training. Respiratory protection may be needed in fire alarm system, they may automatically sound an carrying out an experimental procedure, in dispensing alarm and call the fire department, they may trigger or handling hazardous chemicals, in responding to a an automatic extinguishing system, or they may only chemical spill or release in cleanup decontamination, serve as a local alarm. Because laboratory operations or in hazardous waste handling. may generate heat or vapors, the type and location Under OSHA regulations, only equipment listed of the detectors must be carefully evaluated to avoid and approved by the Mine Safety and Health Ad- frequent false alarms. ministration and NIOSH may be used for respiratory protection. Also under the regulations, each site on 7.F.2.3.3 ire Hoses F which respiratory protective equipment is used must Fire hoses are intended for use by trained firefighters implement a respirator program (including training against fires too large to be handled by extinguishers and medical certification) in compliance with OSHA’s and are included as safety equipment in some struc- Respiratory Protection Standard (29 CFR § 1910.134); tures. Water has a cooling action and is effective against see also ANSI standard Z88.2-1992, Practices for Respi- fires involving paper, wood, rags, and trash (Class A ratory Protection. fires). Do not use water directly on fires that involve Respirators must fit snugly on the face to be effec- live electrical equipment (Class C fires) or chemicals tive. Conduct tests for a proper fit prior to selection of such as alkali metals, metal hydrides, and metal alkyls a respirator and verify before the user enters the area that react vigorously with water (Class D fires). of contamination. Failure to achieve a good face-to-face Do not use streams of water against fires that in- piece seal (e.g., because of glasses or facial hair) can volve oils or other water-insoluble flammable liquids permit contaminated air to bypass the filter and create (Class B fires). Water will not readily extinguish such a dangerous situation for the user. For individuals with
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179 WORKING WITH LABORATORY EQUIPMENT facial hair, do not use respirators requiring a face-to- 2. Organic vapor cartridges cannot be used for va- face piece seal. In such cases, powered, air-purifying, pors that are not readily detectable by their odor or supplied-air respirators may be appropriate. or other irritating effects or for vapors that will generate substantial heat on reaction with the 7.F.2.4.1 ypes of Respirators T sorbent materials in the cartridge. Several types of non-emergency respirators are 3. D ust, fumes, and mist respirators are used available for protection in atmospheres that are not only for protection against particular, or certain immediately dangerous to life or health but that could classes of, dusts, fumes, and mists as specified be detrimental after prolonged or repeated exposure. by the manufacturer. The useful life of the filter Other types of respirators are available for emergency depends on the concentration of contaminant or rescue work in hazardous atmospheres from which encountered. Such particulate-removing respira- the wearer needs protection. Additional protection tors usually trap the particles in a filter composed may be required if the airborne contaminant could be of fibers; they are not 100% efficient. Respirators absorbed through or irritate the skin. For example, the of this type are generally disposable. Examples possibility of eye or skin irritation may require the use are surgical masks and toxic-dust and nuisance- of a full-body suit and a full-face mask rather than a dust masks. Some masks are NIOSH-approved half-face mask. For some chemicals the dose from skin for more specific purposes such as protection absorption can exceed the dose from inhalation. against simple or benign dust and fibrogenic The choice of the appropriate respirator in a given dusts and asbestos. Particulate-removing res- situation depends on the type of contaminant and its pirators afford no protection against gases or estimated or measured concentration, known exposure vapors and may give the user a false sense of limits, and hazardous properties. The degree of protec- security. They are also subject to the limitations tion afforded by the respirator varies with the type. Six of fit. main types of respirators are currently available: 4. Supplied-air respirators deliver fresh air to the face piece of the respirator at a pressure high 1. Chemical cartridge respirators are only for pro- enough to cause a slight buildup relative to at- tection against particular individual (or classes mospheric pressure. As a result, the supplied air of) vapors or gases as specified by the respirator flows outward from the mask, and contaminated manufacturer and cannot be used at concentra- air from the work environment cannot readily tions of contaminants above that specified on the enter the mask. This characteristic renders face- cartridge. Also, these respirators cannot be used to-face piece fit less important than with other if the oxygen content of the air is less than 19.5%, types of respirators. Fit testing is, however, re- in atmospheres immediately dangerous to life, or quired before selection and use. for rescue or emergency work. These respirators 5. Supplied-air respirators are effective protection function by trapping vapors and gases in a car- against a wide range of air contaminants (gases, tridge or canister that contains a sorbent material, vapors, and particulates) and are used in oxygen- with activated charcoal being the most common deficient atmospheres. Where concentrations of adsorbent. Because significant breakthrough air contaminants could be immediately danger- can occur at a fraction of the canister capacity, ous to life, such respirators can be used provided knowledge of the potential workplace exposure (a) the protection factor of the respirator is not ex- and length of time the respirator will be worn ceeded and (b) the provisions of OSHA’s Respi- is important. Replacing the cartridge after each ratory Protection Standard (which indicates the use ensures the maximum available exposure need for a safety harness and an escape system time for each new use. Difficulty in breathing or in case of compressor failure) are not violated. the detection of odors indicates plugged or ex- The air supply of this type of respirator must be hausted filters or cartridges or concentrations of kept free of contaminants (e.g., by use of oil filters contaminants higher than the absorbing capacity and carbon monoxide absorbers). Most labora- of the cartridge, and the user should immedi- tory air is not suitable for use with these units ately leave the area of contamination. Check and because these units usually require the user to clean chemical cartridge respirators on a regular drag lengths of hose connected to the air supply basis. Do not store new and used cartridges near and they have a limited range. chemicals because they are constantly filtering 6. SCBA is the only type of respiratory protective the air. Store them in sealed containers to prevent e quipment suitable for emergency or rescue chemical contamination. work. Untrained personnel should not attempt to use one.
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180 PRUDENT PRACTICES IN THE LABORATORY if necessary, the eyes can be washed while the body is 7.F.2.4.2 rocedures and Training P showered. Each area where respirators are used should have written information available that shows the limita- 7.F.2.5.3 utomatic External Defibrillators (AED) A tions, fitting methods, and inspection and cleaning pro- AED owners should provide or arrange for training cedures for each type of respirator available. Personnel and refresher training. Staff that may be on-site dur- who may have occasion to use respirators in their work ing normal working hours and available to operate must be thoroughly trained before initial use and an- AED equipment should be selected for this training. nually thereafter in the fit testing, use, limitations, and The training should be an American Heart Association care of such equipment. Training includes demonstra- cardiopulmonary resuscitation (CPR)/AED course tions and practice in wearing, adjusting, and properly or a nationally acceptable equivalent. Competency is fitting the equipment. OSHA regulations require that a determined by the certified course instructor. Train- worker be medically certified before beginning work in ing records, including a description of the training an area where a respirator must be worn [OSHA Respi- program and refresher training schedule, should be ratory Protection Standard, 29 CFR § 1910.134(b)(10)]. documented. AED owners should be familiar with lo- cal laws concerning training and use of these devices. 7.F.2.4.3 nspections I Respirators for routine use should be inspected be- fore each use by the user and periodically by the labo- 7.F.2.6 Storage and Inspection of Emergency ratory supervisor. Self-contained breathing apparatus Equipment should be inspected at least once a month and cleaned Establish a central location for storage of emergency after each use. equipment. Include the following: 7.F.2.5 Safety Showers and Eyewash Units • SCBA (for use by trained personnel only), • blankets for covering the injured, 7.F.2.5.1 afety Showers S • stretchers (generally best to wait for qualified Make safety showers available in areas where chemi- medical help to move a seriously injured person), cals are handled; make sure they meet all installation • first-aid equipment (for unusual situations such as and maintenance requirements (ANSI Z358.1 Emer- exposure to hydrofluoric acid or cyanide, where gency Eyewash and Shower Equipment; ANSI, 2004). immediate first aid is required), and Use them for immediate first-aid treatment of chemi- • chemical spill cleanup kits and spill control equip- cal splashes and for extinguishing clothing fires. All ment (e.g., spill pillows, booms, shoe covers, and trained laboratory personnel should know where the a 55-gal drum in which to collect sorbed material). safety showers are located in the work area and should (Also consult Chapter 6, sections 6.C.10.5 and learn how to use them. Test safety showers routinely 6.C.10.6.) to ensure that the valve is operable and to remove any debris in the system. Inspect safety equipment regularly (e.g., every 3 to 6 The shower should drench the subject immediately months) to ensure that it will function properly when and be large enough to accommodate more than one needed. The laboratory supervisor or safety coordina- person if necessary. It should have a quick-opening tor is responsible for establishing a routine inspection valve requiring manual closing; a downward-pull system and verifying that inspection records are appro- delta bar is satisfactory if long enough. Chain pulls priately maintained and archived as required by law. are not advisable because they can hit the user and Perform inspections of emergency equipment as be difficult to grasp in an emergency. Install drains follows: under safety showers to reduce the slip and fall risks and facility damage that is associated with flooding in • Inspect fire extinguishers for broken seals, dam- a laboratory. age, and low gauge pressure (depending on type of extinguisher). Check for proper mounting of 7.F.2.5.2 yewash Units E the extinguisher and that it is readily accessible. Eyewash units are required in research or instruc- Some types of extinguishers must be weighed tional laboratories if substances used there present an annually, and periodic hydrostatic testing may be eye hazard or if unknown hazards may be encoun- required. tered. An eyewash unit provides a soft stream or spray • Check SCBA at least once a month and after each of aerated water for an extended period (15 minutes). use to determine whether proper air pressure is Locate these units close to the safety showers so that,
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181 WORKING WITH LABORATORY EQUIPMENT being maintained. Look for signs of deterioration • Render immediate first aid; appropriate measures or wear of rubber parts, harness, and hardware include washing under a safety shower, adminis- and make certain that the apparatus is clean tration of CPR by trained personnel if heartbeat and free of visible contamination. Periodically or breathing or both have stopped, and special perform fit tests to ensure that the mask forms a first-aid measures. good seal to an individual’s face. Masks come in • Put out small fires by using a portable extin- different sizes and cannot be considered universal guisher. Turn off nearby equipment and remove or one-size-fits-all. Facial hair, especially beards, combustible materials from the area. For larger interferes with the mask seal and is not to permit- fires, contact the appropriate fire department ted for SCBA users. promptly. Be aware that many organizations limit • Examine safety showers and eyewash units vi- fire extinguisher use to designated trained person- sually and test their mechanical function. Purge nel only. them as necessary to remove particulate matter • Provide emergency personnel with as much infor- from the water line. mation as possible about the nature of the hazard, • Inspect an AED periodically following the manu- including a copy of the material safety data sheet facturer’s recommendations and procedures as (MSDS). well as after use and before returning to its storage • In a medical emergency, laboratory personnel location. should remain calm and do only what is necessary to protect life. • Summon medical help immediately. 7.G EMERGENCY PROCEDURES • Do not move an injured person unless he or she is The following general emergency procedures are in danger of further harm. recommended in the event of a fire, explosion, spill, • Keep the injured person warm. If feasible, desig- or medical or other laboratory accident. These pro- nate one person to remain with the injured person. cedures are intended to limit injuries and minimize The injured person should be within sight, sound, damage if an accident should occur. Post numbers to or physical contact of that person at all times. call in emergencies clearly at all telephones in hazard • If clothing is on fire and a safety shower is im- areas. Because emergency response (personnel, contact mediately available, douse the person with water; information, procedures) varies greatly from institu- otherwise, roll the person on the floor to smother tion to institution, all laboratory personnel should be the flames. properly trained and informed of the protocols for their • If harmful chemicals have been spilled on the particular institution. body, remove the chemicals, usually by flooding the exposed area with the safety shower, and im- • Have someone call for emergency help, for in- mediately remove any contaminated clothing. stance, 911 or other number as designated by the • If a chemical has splashed into the eye, immedi- institution. State clearly where the accident has ately wash the eyeball and the inner surface of the occurred and its nature. eyelid with water for 15 minutes. An eyewash unit • Ascertain the safety of the situation. Do not enter should be used if available. Forcibly hold the eye or reenter an unsafe area. open to wash thoroughly behind the eyelid. • Without endangering yourself, render assistance • If possible, determine the identity of the chemical to the personnel involved and remove them from and inform the emergency medical personnel at- exposure to further injury. tending the injured person. Provide an MSDS for • Warn personnel in adjacent areas of any potential each chemical that is involved in the incident to risks to their safety. the attending physician or emergency responders.
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