Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 147
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
OCR for page 148
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
OCR for page 149
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-
OCR for page 150
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
OCR for page 151
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).
OCR for page 152
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:
OCR for page 153
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
OCR for page 154
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
OCR for page 155
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
OCR for page 156
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.)
OCR for page 157
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
OCR for page 172
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.
OCR for page 173
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
OCR for page 174
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
OCR for page 175
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
OCR for page 176
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
OCR for page 177
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
OCR for page 178
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
OCR for page 179
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.
OCR for page 180
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,
OCR for page 181
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.
OCR for page 182
