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Electrical Safety in the Lab

While electricity is in constant use by the researcher, both within and outside the laboratory, significant physical harm or death may result from its misuse.

by Lab Manager
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While electricity is in constant use by the researcher, both within and outside the laboratory, significant physical harm or death may result from its misuse.

With direct current, a person can detect a "tingling" feeling at 1 mA and the median "let-go" threshold (the current at which one cannot release the conductor) is 76 mA. For 60 Hertz alternating current, the values are 0.4 mA and 16 mA, respectively. Women are more sensitive to the effects of electrical current; approximately 2/3 of the current is needed to produce the same effect. Higher currents produce respiratory inhibition, then ventricular fibrillation, and ultimately cardiac arrest.

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If an electrical hazard is suspected, the device in question should be disconnected immediately and the cause ascertained by a person competent in such matters. Work on electrical devices should be done only after the power has been shut off in such a manner that it cannot be turned on accidentally. Since malfunctioning equipment may contain shorts, merely turning off the equipment is not sufficient to prevent accidents. Equipment should be unplugged before being inspected or the circuit the equipment is wired to deactivated by putting the circuit breaker in the off position or removing the fuse. Equipment wired to a safety switch should be turned off at the safety switch. Internal energy storage devices such as capacitors must be discharged.

All electrical wiring and construction must conform to standard safety practice. The minimum safety practice must conform to the coded regulations of the City of Columbus and the State of Ohio. High voltage equipment must be labeled: Danger, High Voltage. Switches to turn off all electrical power to the equipment in case of emergency should be prominently labeled.  

The following are a list of rules for working with electrical equipment:

  1. Turn off the power to equipment before inspecting it. Turn off circuit breakers or unplug the equipment. To turn off a safety switch, use your left hand (wear insulating gloves made of leather or heavy cotton or rubber), turn your face away from the box, and pull the handle down. Circuits may discharge violently when being turned on or off and the cover to the junction box may be blown open.
  2. Use only tools and equipment with non-conducting handles when working with electrical devices.
  3. All current transmitting parts of any electrical devices must be enclosed.
  4. When checking an operating circuit, keep one hand either in a pocket or behind your back to avoid making a closed circuit through the body.
  5. Maintain a work space clear of extraneous material such as books, papers, and clothes.
  6. Never change wiring with circuit plugged into power source.
  7. Never plug leads into power source unless they are connected to an established circuit.
  8. Avoid contacting circuits with wet hands or wet materials.
  9. Wet cells should be placed on a piece of non-conducting material.
  10. Check circuits for proper grounding with respect to the power source.
  11. Do not insert another fuse of larger capacity if an instrument keeps blowing fuses - this is a symptom requiring expert repairs. If a fuse blows, find the cause of the problem before putting in another one.
  12. By the Ohio Fire Code, extension cords must be connected to a power strip equipped with a fuse.
  13. Do not use or store highly flammable solvents near electrical equipment.
  14. Multi-strip outlets (cube taps) should not be used in place of permanently installed receptacles. If additional outlets are required have them installed by an electrician.
  15. Keep access to electrical panels and disconnect switches clear and unobstructed.

Static Electricity and Spark Hazards:

Sparks may result in explosions in areas where flammable liquids are being used and therefore proper grounding of equipment and containers is necessary. Some common potential sources of sparks are:

  1. The making and braking of an electrical circuit when the circuit is energized.
  2. Metal tanks and containers.
  3. Plastic lab aprons.
  4. Metal clamps, nipples, or wire used with nonconducting hoses.
  5. High pressure gas cylinders upon discharge.