Basic Electrical Safety

Electricity is a form of energy and source of power used directly and indirectly that has the capability of causing injury. There may not be a second chance when you make a mistake with electricity. Even household current (120 volts) can stop your heart.

Thousands of electrical injuries including deaths occur in the US ever year. Several studies indicate that between 20 and 35 percent of all electrical injuries go unreported. (US Bureau of Labor Statistics).

UW personnel need to be aware of the hazards electricity poses and the ways to either eliminate or control those hazards.

Electrical Hazards


Burns from electricity are the most common shock-related injuries and are one of three types: Electrical, arc/flash or thermal contact. Electrical burns occur when electric current flows through tissues or bone, generating heat that causes tissue damage. They are among the most serious burns and require immediate medical attention. Arc or flash burns result from high temperatures caused by an electric arc or explosion near the body and require prompt treatment. Thermal contact burns are caused when the skin touches hot surfaces of overheated electric conductors, conduits, or other energized equipment, as well as when clothing catches on fire. Clothing may catch on fire when an electric arc is produced.


Shock results when the body becomes part of the electrical circuit; current enters the body at one point and leaves at another. Electrical shock is defined as a reflex response to the passage of electric current through the body.


Electrocution results when a person is exposed to a lethal amount of electrical energy.


An arc flash is the sudden release of electrical energy through the air when a high-voltage gap exists and there is a breakdown between conductors. An arc flash gives off thermal radiation (heat) and bright, intense light that can cause burns. Temperatures have been recorded as high as 35,000 °F. High-voltage arcs can also produce considerable pressure waves by rapidly heating the air and creating a blast.


Electrical fires may be caused by: drawing too much current through fixed wiring where overcurrent protection fails or does not exist, faulty electrical outlets, poor wiring connections, and old wiring. They may also result from problems with cords (such as extension and appliance cords), plugs, receptacles, and switches.


An explosion can occur when electricity ignites an explosive mixture of material in the air and results in a sudden release of energy. This can happen due to a short circuit, leakage of current.

Secondary Injuries

Secondary injuries could result from a surge of electrical energy that results in a forceful muscle contraction and/or fall. The resulting injury can be a soft tissue injury, soft tissue tear, and/or broken bone(s).

Electrical Grounding

plug missing grounding prongElectrical grounding is a safety measure used to help prevent people from accidentally coming in contact with electrical energy. Electrical grounding provides an alternate path for electricity to follow rather than going through a person. This helps to prevent accidents and possible death. The plug shown on the left is missing its grounding pin-which was likely broken off and it should also be discarded.

double insulated wire diagramCords for portable electrical equipment must be grounded or double insulated to prevent shock. For most equipment and items that are powered by a building’s electrical service, this means that the grounding pin (or prong) must be present to be properly grounded. Properly double insulated power tools will have a symbol and/or may have a statement designating that they are “Double Insulated."

Equipment with a grounding prong must be plugged into an extension cord with a ground and the grounding plug should not be removed from equipment.

A cheater plug that plugs into a wall receptacle with 2 prongs and has 3 prongs should never be used as it is not properly grounded.

cheater plug--never to be used!


Ground-Fault Circuit Interrupter (GFCI)

Receptacle GFCITo prevent electrical shock, if an electrical outlet is to be used in an area that is wet, it must be protected by a Ground-Fault Circuit Interrupter (GFCI) device that is built into the outlet itself. The GFCI is used to ensure that the worst results from one becoming a path to the ground is brief with at most a 5 mA shock, which is painful but not fatal because the GFCI with create a ground fault, leakage in current.

If the outlet is within six feet of a sink, spigot or other area where moisture is present or concentrated, it should be GFCI protected. Some spaces such as bathrooms and kitchens have specific rules defining where and when GFCI devices are to be used. Using a GFCI is very important because water with impurities is a great conductor, which means that it is dangerous to use electrical equipment near or around water and extra protection is needed.

To prevent shocks, electrical equipment used in outdoor or other wet locations must be directly plugged into a GFCI protected outlet designed for this use.
Extension cords and temporary lights (drop lights, shop lights, etc.) used outdoors or in other wet locations must have built-in GFCI protection devices.

Common GFCI's are:

Receptacles (pictured above)
Outlet adaptor GFCIThis type of GFCI is used in place of the standard duplex receptacle. It fits into the standard outlet box and protects you against “ground faults” whenever an electrical product is plugged into the outlet. Most receptacle-type GFCIs can be installed so that they also protect other electrical outlets farther downstream in the branch circuit.

Outlet (receptacle) Adapters
This type of GFCI can be plugged into a grounded receptacle to provide protection against ground faults whenever an electrical product is plugged into the adaptor. Older buildings are not equipped with receptacle type GFCIs so outlet adaptors are a good option. The GFCI Outlet Adaptor is a cheap and easy way to have GFCI protection. It can be purchased on Amazon at www.amazon.com/GFCI-Outlet-Adapters-Single-Adapter/dp/B001OE3JHC or via another retailer.

Circuit breaker GFCI Circuit Breaker
In buildings equipped with circuit breakers (not fuses), a circuit breaker GFCI may be installed in a panel box to protect selected circuits. The circuit breaker GFCI will shut off electricity in the event of a “ground-fault”, and it will trip when a short circuit or overload occurs. This protection covers the wiring and each outlet, lighting fixture, heater, etc., served by the branch circuit protected by the GFCI in the panel box.

Portable GFCIPortable
Where permanent GFCIs are not practical, portable GFCIs may be used. One type contains the GFCI circuitry in a plastic enclosure with plug blades in the back and receptacle slots in the front. This is plugged into a receptacle, and then the electrical product is plugged into the GFCI. Another type of portable GFCI is an extension cord combined with a GFCI


High Amperage Equipment

High amperage equipment must be plugged directly into permanent wall receptacles. No extension cords, or other devices that prevent high amperage equipment from being plugged into wall receptacles may be used. High amperage equipment includes equipment that draws power, creates heat, and/or uses a motor like a portable electric space heater, refrigerators, icemakers, freezers, microwaves, pumps, compressors, portable air conditioners.

Flexible Electric Cords & Power Strips

Flexible electric cords include installed wiring, equipment wiring and extension cords. Prior to use of any electrical cord or power strip, it must be visually inspected for damage. Damage to the outer layer of insulation itself may be repaired with electrical tape. If damage extends beyond the outer layer of cord (i.e. if the conductor is exposed), then the extension cord and/or power strip must be discarded.

The damage to cords often occurs because they are improperly protected. There are several key things to remember to protect a cord. These actions will greatly decrease the risk of electrical shock and fire.

  • Don’t attach flexible cords to building structures. It is especially important to not use methods such as nails, tacks, zip-ties, staples or other methods which may in fact damage cords.
  • Don’t run flexible cords through walls, ceilings, floors, or windows, over drop down ceilings, or under doors, floor coverings (carpets or rugs), or false floors. In addition to being a fire code violation, the condition and use of the cord cannot be monitored or protected if it is hidden from view.
  • If you must place a flexible cord across or near a walkway, ensure you use a transitional strip designed for the task. Other methods, such as duct tape, are not designed to protect the cord and usually do more to damage the cord than protect it.
  • Never place cords where they will be driven over by a vehicle of any kind.
  • Don’t place cords over sharp or abrasive materials.
  • Never kink, knot or twist cords.
  • Never use cords as a rope to pull or bind things.
  • Always use the plug to disconnect a cord from another outlet.

Extension Cords and Multiple-Plug Adaptors

Daisy-chained multi-plug outlets
  • Must be Underwriters Laboratory (UL)-approved.
  • Must be plugged directly into mounted electrical receptacles.
  • No daisy-chained cords or multi-plug outlets, which means that one extension cord, or multi-plug outlet may not be plugged into another. An example of a daisy chain is pictured to the right, this is not permitted.
  • Shall not be used in conjunction with refrigerators, ice machines, portable electric space heaters, coffee pots, microwaves, or similar heat producing and/or high amperage devices.
  • Shall not be used where flammable or explosive atmospheres exist.
  • Multiple-plug adaptors must have a resettable circuit breaker (power switch). An example of a Multi-plug (cube) adaptors below; its use is not permitted as it does not have a resettable circuit breaker (power switch).

Multi-plug (cube) adaptor without resettable circuit breakerUnsafe use of extension cords has been and remains one of the most wide-spread safety issues at UW. While surge suppressor with built in circuit breakers may remain in place and used perpetually, extension cords may not be remain in place for permanent power supply. They should only be used for a short event or work shift. In rare cases it may be possible to use extension cords in lieu of permanent wiring for up to 90 days.

If more outlets are required in your space to eliminate the number and duration of use of temporary extension cords, contact your facilities department for assistance and building improvements.



Circuit Breaker

All building electrical circuit breaker panels require at least three feet depth of clearance in front of the panel, and not less than 30 inches of clearance in width.

Do not try to access, use or alter any building’s electrical service-including circuit breaker panels unless you are specifically qualified and authorized by your facilities department to do so.Uncovered junction box

Open Junction Boxes

Make sure that all junction boxes are completely covered in order to ensure injury does not occur. Junction boxes enclose electrical connections in order to prevent tampering and deterioration. They keep these electrical connections out of sight. The image below is of an example of an uncovered junction box. This is not permitted.

Lockout/Tagout (LOTO)

When servicing and maintenance tasks involve electricity and electrical equipment, people can be injured by the unexpected startup of equipment or release of stored energy. In these situations, LOTO procedures, or another form of hazardous energy control, should be used to prevent serious or fatal injuries.

More information is available on the UW EH&S Lockout/Tagout Web page.

EH&S Responsibility & Training

EH&S is responsible to help departments identify risk and provide consultation and support to improve their safety.

For assistance, contact EH&S at (206) 616-6261.

EH&S also provides online training on electrical safety: Training for Basic Electrical Safety, and Electric Arc Flash Awareness - Online.

Accident Reporting

All injuries and near-misses, including those potentially caused by electricity or electrical equipment, must be reported using the Online Accident Reporting System (OARS).


Seattle DPD - 2012 Seattle Fire Code, Chapter 6 Building Services and Systems (Seattle.gov, PDF)

More Information

Controlling Electrical Hazards (OSHA)

Burn Injury Facts (WA L&I, PDF)

Laboratory Safety: Electrical Hazards (OSHA, PDF)

GFCI information (OSHA)

GFCI information (UW Facilities Services, PDF)

Extension Cord Brochure (UW Facilities Service, PDF)

Fast Facts: Power Strips and Dangerous Daisy Chains (Office of Compliance, PDF)

Construction Safety and Health: Electrical Safety Workbook (OSHA, PDF)