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Prudent Practices in the Laboratory: Handling and Disposal of Chemicals
Proper use of laboratory equipment is required to work safely with hazardous chemicals. Maintenance and regular inspection of laboratory equipment are an essential part of this activity. Many of the accidents that occur in the laboratory can be attributed to improper use or maintenance of laboratory equipment. This chapter discusses prudent practices for handling the apparatus often used in laboratories.
The most common equipment hazards in laboratories come from electrically powered devices, and these are followed by hazards with devices for work with compressed gases and high/low pressures and temperatures. Other physical hazards include electromagnetic radiation hazards from such equipment as lasers and radio-frequency generating devices. Seemingly ordinary hazards such as floods from water-cooled equipment, accidents with rotating equipment and machines or tools for cutting and drilling, noise extremes, slips, trips, and falls, lifting, and poor ergonomics probably account for the greatest frequency of laboratory accidents and injuries.
6.BWORKING WITH WATER-COOLED EQUIPMENT
The use of cooling water in laboratory condensers and other equipment is common laboratory practice, but can create a flooding hazard. The most common source of the problem is disconnection of the tubing supplying the water to the condenser. Hoses can pop off under irregular flows when building water pressure fluctuates or can break when the hose material has deteriorated from long-term use. Floods also result when exit hoses jump out of the sink from a strong flow pulse or sink drains are blocked by an accumulation of extraneous material. Proper use of hose clamps and maintenance of the entire cooling system or alternate use of a portable cooling bath with suction feed can resolve such problems. Plastic locking disconnects can make it easy to disconnect water lines without having to unclamp and reclamp secured lines. Some quick disconnects also incorporate check valves, which when disconnected do not allow flow into or out of either half of the connection. This feature allows for disconnecting and reconnecting with minimal spillage of water.
6.CWORKING WITH ELECTRICALLY POWERED LABORATORY EQUIPMENT
Electrically powered laboratory equipment is used routinely for laboratory operations requiring heating, cooling, agitation or mixing, and pumping. Electrically powered equipment found in the laboratory includes fluid and vacuum pumps, lasers, power supplies, both electrophoresis and electrochemical apparatus, x-ray equipment, stirrers, hot plates, heating mantles, and, more recently, microwave ovens and ultrasonicators. Attention must be paid to both the mechanical and the electrical hazards inherent in these devices. High voltage and high power requirements are increasingly prevalent; therefore prudent practices for handling these devices are increasingly necessary.
Electric shock is the major electrical hazard. A relatively low current of 10 milliamperes (mA) poses some danger, and 80 to 100 mA can be fatal. In addition, if improperly used, electrical equipment can serve as an ignition source for flammable or explosive vapors. Most of the risks involved can be minimized by regular, proper maintenance and a clear understanding of the correct use of the device.
Particular caution must be exercised during installation, modification, and repair, as well as during use of the equipment. In order to ensure safe operation, all electrical equipment must be installed and maintained in accordance with the provisions of the National Electrical Code (NEC) of the National Fire Protection Association (NFPA, 1991a). Laboratory workers should also consult state and local codes and regulations, which may contain special provisions and be more stringent than the NEC and NFPA rules. All repair and calibration work on electrical equipment must be carried out by properly trained and qualified personnel. Before modification, installation, or even minor repairs of electrical equipment 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 OSHA Control of Hazardous Energy Standard (29 CFR 1910.147; Lock out/Tag out) applies).
It is imperative that each person participating in any experiment involving the use of electrical equipment be aware of all applicable equipment safety issues and be briefed on any potential problems. Workers can significantly reduce hazards and dangerous behavior by following some basic principles and techniques: checking and rechecking outlet receptacles (section 6.C.1.1), making certain that wiring complies with national standards and recommendations (section 6.C.1.2), and reviewing general precautions (section 6.C.1.3) and personal safety techniques (section 6.C.1.4).
6.C.1.1 Outlet Receptacles
All 110-volt (V) outlet receptacles in laboratories should be of the standard design that accepts a three-