Electrical Safety

To safeguard against injury when using electrical equipment, requirements and standards have been established through the implementation of nationally recognized codes, approval tests and electrical safety work practices. All Installed equipment must be tested and listed by one of the Nationally Recognized Testing Laboratories


All electrical equipment must be installed and maintained in accordance with the following standards:


 


Electrical Safety Reminders


  • Only licensed electricians are permitted to work on electrical systems and equipment that use or control electrical power.
  • Do not operate electrical tools or equipment in wet areas or areas where potentially flammable dusts, vapors, or liquids are present, unless specifically approved for the location.
  • Should a circuit breaker or other protective device "trip" ensure that a licensed electrician checks the circuit and equipment and corrects problems before resetting the breaker.
  • Report hazards (lack of protective guards or covers, damaged equipment, etc.) to the building manager, Department of Facilities, Environment Health and Safety department or supervisor immediately.
  • Discard any piece of equipment that gives you even the slightest shock. If the resistance through your body is lowered  i.e. standing in water or touching metal, even the slightest shock can be deadly.
  • Do not leave electrical boxes, switch-gear, cabinets, or electrical rooms open when not directly attended. Insulate energized parts when covers have been removed or doors are ajar. The use of cardboard, plywood, or other flammable materials to cover energized circuits is prohibited.
  • Junction boxes and electrical panels need to have proper covers in place to conceal all wiring.  Hard wiring should not be exposed/accessible to non-electrical employees.
  • Re-route electrical cords or extension cords so they don't run across the aisle/corridor or over pipes or through doors.
  • Never use electrical equipment in or around water.
  • De-energize equipment before removing any protective covers or guards.  
  • Don't use an electrical outlet or switch if the protective cover is ajar, cracked, or missing.
  • Remove any combustible materials, such as paper and wood from the area. Be sure flammable liquids and gases are secured away from the area when the appliance is in use.
  • Never put conductive metal objects into energized equipment.
  • Remove cord from the outlet by pulling the plug instead of pulling on the cord.
  • Don't carry equipment by the cord - only by the handle or base.
  • Be sure extension cords are properly rated for the job and used only temporarily.
  • Use extension cords with 3-prong plugs to ensure the equipment is grounded. Never remove the grounding post from a 3-prong plug so you can put it into a 2-prong.
  • Don't overload extension cords, multi-outlet strips or wall outlets.
  • Take seriously any warning signs, barricades or guards posted when electrical equipment is being repaired, installed, etc.

 


Factors Involved In Electrical Shock


  • THE QUANTITY OF CURRENT FLOWING THROUGH THE BODY 

    Current (amperes) is the killing factor in electrical shock, not the voltage. The voltage only determines how much current will flow through a given body resistance. In general, the body's resistance to electrical shock is minimal (150,000 to 600,000 Ohms.) Even contact with standard 110-volt circuits can be lethal under certain conditions. Refer to the chart below.
  • THE CURRENT PATH THROUGH THE BODY FROM ENTRY TO EXIT 

    Hand-to-hand, hand- or head-to-foot, and ear-to-ear current paths are the most dangerous because they may cause severe damage to the heart, lungs and brain. This is why it is important not to wear metal jewelry, not to lean against or use both hands on electrical equipment so as not to become part of the circuit.

     
  • THE LENGTH OF TIME THE BODY IS IN THE CIRCUIT 

    The longer the body is in the circuit, the greater the damage. You may be unable to let go of a 15 to 20 milliampere current. The body temperature may increase possibly damaging tissues, bones, and organs.

 


CURRENT IN MILLIAMPS                                                                      EFFECTS OF 60 HZ CURRENT PASSING THROUGH


                                                                                                                 THE BODY


1 or less 5                                                                                                 May not be felt - Maximum harmless intensity


1 to 8                                                                                                         Sensation of mild shock, can let go at will


8 to 15                                                                                                       Painful shock, muscles contract, may still be able to let go


15 to 20                                                                                                     Painful shock, can NOT let go


20 to 75                                                                                                     Intense pain, breathing may be paralyzed


100 to 200                                                                                                 Ventricular fibrillation; holds unconscious victim to the circuit,


                                                                                                                  could be fatal


200 or more                                                                                               Heart stops, muscles contract intensely & could break bones,


                                                                                                                  severe burns, breathing stops


 


 


Wiring, Grounding, Insulation


 


Wiring


All electrical installations or the replacement, modification, repair or rehabilitation of any electrical installation must comply with the requirements of the National Electrical Code (NEC) of theNational Fire Protection Association, and/or the U.S. Department of Labors’ Occupational Safety and Health Administration.


For permanent equipment and or permanent wiring contact the Department of Facilities Electrical Services Manager at: http://web.mit.edu/facilities/


Grounding


All equipment should be grounded and fused in accordance with NEC. All extension and power cords must have a grounding pin.


Ground Fault Circuit Interrupters (GFCI)


  • GFCIs are designed to protect people from an electric shock.
  • A GFCI works by detecting a current drop from the hot to the neutral wiring in a circuit. When the GFCI senses approximately a 5ma difference it shuts down the circuit in 1/40 of a second.
  • GFCIs must be installed wherever a water hazard is present.
  • GFCIs can be at the breaker, the outlet, incorporated with the plug of the appliance/piece of equipment, or part of a short extension cord.

Insulation


All electrical equipment should be properly insulted. Any power cords that are frayed must be discarded and any live/hot wires should be insulated to prevent danger of electrical shock.


National Consensus Standards For Design And Installation


All electrical equipment must be installed and maintained in accordance with the following standards:


National Electrical Code (NEC)® -supported by the NFPA provides electrical safety requirements for wiring methods used in the workplace, for live electric supply and communication lines and equipment for employees in the workplace.