7.A INTRODUCTION

Working safely with hazardous chemicals requires proper use of laboratory equipment. Maintenance and regular inspection of laboratory equipment are essential parts 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 equipment used frequently in laboratories.

The most common equipment-related hazards in laboratories come from devices powered by electricity, devices for work with compressed gases, and devices for high or low pressures and temperatures. Other physical hazards include electromagnetic radiation from 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, falls, lifting, and poor ergonomics account for the greatest frequency of laboratory accidents and injuries. Understandably, injuries to the hands are very common in the laboratory. Care should be taken to use appropriate gloves when handling laboratory equipment to protect against electrical, thermal, and chemical burns, cuts, and punctures.

7.B WORKING WITH WATER-COOLED EQUIPMENT

The use of water as a coolant in laboratory condensers and other equipment is common practice. Although tap water is often used for these purposes, this practice should be discouraged. In many localities conserving water is essential and makes tap water inappropriate. In addition, the potential for a flood is greatly increased. Refrigerated recirculators can be expensive, but are preferred for cooling laboratory equipment to conserve water and to minimize the impact of floods. 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 must be cleaned thoroughly to prevent slips and falls.

Most flooding occurs when the tubing supplying the water to the condenser disconnects. Hoses can pop off when building water pressure fluctuates, causing irregular flows, or can break when the hose material has deteriorated from long-term or improper 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 alternative use of a portable cooling bath with suction feed can resolve such problems. Plastic locking disconnects can make it easy to unfasten water lines without having to unclamp and reclamp secured lines. Some quick disconnects also incorporate check valves, which do not allow flow into or out of either half of the connection when disconnected. This feature allows for disconnecting and reconnecting with minimal spillage of water. To reduce the possibility of overpressurization of fittings or glassware, consider installing a vented pressure relief device on the water supply. Interlocks are also available that shut off electrical power in the event of loss of coolant flow and are recommended for unattended operations.

7.C WORKING WITH ELECTRICALLY POWERED LABORATORY EQUIPMENT

Electrically powered 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, microwave ovens, and ultrasonicators. Attention must be paid to both the mechanical and the electrical hazards inherent in using 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. Although relatively low current of 10 mA poses some danger, 80 to 100 mA can be fatal. In addition, if improperly used, electrical equipment can ignite flammable or explosive vapors. Most of the risks can be minimized by regular proper maintenance and a clear understanding of the correct use of the device. Before beginning any work, all personnel should be shown and trained in the use of all electrical power sources and the location of emergency shutoff switches. Information about emergency procedures can be found in section 7.G.

7.C.1 General Principles

Particular caution must be exercised during installation, modification, and repair, as well as during use of the equipment. 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, 2008). Trained laboratory personnel should also consult state and local codes and regulations, which may contain special provisions and be more stringent than the NEC 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 equip-



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