• Because series-wound motors cannot be modified to make them spark-free, do not use appliances (e.g., kitchen refrigerators, mixers, and blenders) with such motors in laboratories where flammable materials may be present.
• When bringing ordinary electrical equipment such as vacuum cleaners and portable electric drills having series-wound motors into the laboratory for special purposes, take specific precautions to ensure that no flammable vapors are present before such equipment is used (see Chapter 6, section 6.G).
• Locate electrical equipment to minimize the possibility of spills onto the equipment or flammable vapors carried into it. If water or any chemical is spilled on electrical equipment, shut off the power immediately at a main switch or circuit breaker and unplug the apparatus using insulated rubber gloves.
• Minimize condensation that may enter electrical equipment if it is placed in a cold room or a large refrigerator. Cold rooms pose a particular risk in this respect because the atmosphere is frequently at a high relative humidity, and the potential for water condensation is significant.
• If electrical equipment must be placed in such areas, mount the equipment on a wall or vertical panel. This precaution reduces, but does not eliminate, the effects of condensation.
• Condensation can also cause electrical equipment to overheat, smoke, or catch fire. In such a case, shut off the power to the equipment immediately at a main switch or circuit breaker and unplug the apparatus using insulated rubber gloves.
• To minimize the possibility of electrical shock, carefully ground the equipment using a suitable flooring material, and install GFCIs.
• Always unplug equipment before undertaking any adjustments, modifications, or repairs (with the exception of certain instrument adjustments as indicated in section 7.C.7). When it is necessary to handle equipment that is plugged in, be certain hands are dry and, if feasible, wear nonconductive gloves and shoes with insulated soles.
• Ensure that all laboratory personnel know the location and operation of power shutoffs (i.e., main switches and circuit breaker boxes) for areas in which they work. Voltages in breaker boxes may present an arc or flash hazard. Only qualified personnel wearing proper personal protective equipment (PPE) are allowed to open these boxes to access the main switches and circuit breakers contained therein. Label high-voltage breaker boxes presenting an arc or flash hazard. Trained laboratory personnel should be familiar with, and have in place, alternative power shutoffs (i.e., properly installed crash buttons, ready access to equipment power cord plugs).
• After making modifications to an electrical system or after a piece of equipment has failed, do not use it again until it has been cleaned and properly inspected.
All laboratories should have access to a qualified technician who can make routine repairs to existing equipment and modifications to new or existing equipment so that it will meet acceptable standards for electrical safety. The NFPA National Electrical Code Handbook (NFPA, 2008) provides guidelines.
7.C.1.4 Personal Safety Techniques for Use with Electrical Equipment
When operating or servicing electrical equipment, be sure to follow basic safety precautions as summarized below.
• Inform each individual working with electrical equipment of basic precautionary steps to take to ensure personal safety.
• Avoid contact with energized electrical circuits. Let only qualified individuals service electrical equipment.
• Before qualified individuals service electrical equipment in any way, disconnect the power source to avoid the danger of electric shock. Ensure that any capacitors are, in fact, discharged.
• Before reconnecting electrical equipment to its power source after servicing, check the equipment with a suitable tester, such as a multimeter, to ensure that it is properly grounded.
• Do not reenergize a circuit breaker until sure that the cause of the short circuit has been corrected.
• Install GCFIs as required by code to protect users from electric shock, particularly if an electrical device is handheld during a laboratory operation.
• If a person is in contact with a live electrical conductor, disconnect the power source before removing the person from the contact and administering first aid.
7.C.1.5 Additional Safety Techniques for Equipment Using High Current or High Voltage
Unless laboratory personnel are specially trained to install or repair high-current or high-voltage equipment, reserve such tasks for trained electrical workers. The following reminders are included for qualified personnel: