Ensure the complete electrical isolation of electrical equipment and power supplies. Enclose all power supplies in a manner that makes accidental contact with power circuits impossible. In every experimental setup, including temporary ones, employ suitable barriers or enclosures to protect against accidental contact with electrical circuits.

Equip motor-driven electrical equipment used in a laboratory where volatile flammable materials may be present (e.g., a hydrogenation room) with either nonsparking induction motors that meet Class 1, Division 2, Group C-D electrical standards (U.S. DOC, 1993) or air motors instead of series-wound motors that use carbon brushes, such as those generally used in vacuum pumps, mechanical shakers, stirring motors, magnetic stirrers, and rotary evaporators.

Do not use variable autotransformers to control the speed of an induction motor because such operation will cause the motor to overheat and perhaps start a fire.

Because series-wound motors cannot be modified to make them spark-free, do not use kitchen appliances (refrigerators, mixers, blenders, and so on) 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 5, section G).

Locate electrical equipment so as 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.

Minimize the 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 will reduce, though not eliminate, the condensation problem.

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.

To minimize the possibility of electrical shock, carefully ground the equipment using a suitable flooring material, and install ground-fault circuit interrupters (GFCIs).

Always unplug equipment before undertaking any adjustments, modifications, or repairs (with the exception of certain instrument adjustments as indicated in section 6.C.7). When it is necessary to handle equipment that is plugged in, be certain hands are dry