Dear Mr. Electrician:  What are the effects of electricity to the human body?

Answer:  Below is a chart that was compiled many years ago.  It explains the effects of electricity on the human body when receiving electrical shocks of different intensities.  Do not try this yourself or on other people.

EFFECTS OF ELECTRICITY ON HUMANS

Amount
of Electrical Current
Reaction to
the Human Body
Below 1 milliampere Generally not perceptible
1 milliampere Faint tingle
5 milliamperes Slight shock felt; not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries
6–25 milliamperes (women) Painful shock, loss of muscular control*
9–30 milliamperes (men) The freezing current or “let-go” range.*

Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.
50–150 milliamperes Extreme pain, respiratory arrest, severe muscular contractions. Death is possible.
1,000–4,300 milliamperes Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely
10,000 milliamperes Cardiac arrest, severe burns; death probable


*
If the extensor muscles are excited by the shock, the person may be thrown away from the power source.
NOTE: 1000 milliamperes equals one ampere which is approximately the amount of current that flows through a 120 watt light bulb at 120 volts.  
Source: W.B. Kouwenhoven, “Human Safety and Electric Shock,” Electrical Safety Practices, Monograph, 112, Instrument Society of America, p. 93. November 1968.

 

Below is a tragic story of a girl who got electrocuted in the bath tub.  Please do not use extension cords in the bathroom.  I was on a repair call for a bathroom fan once when I noticed that my elderly client had an electric heater next to his bath tub.  It was plugged into a GFCI outlet with an extension cord.  In addition to an electrical hazard, the extension cord on the floor was a tripping hazard.  I tried to explain the electrical hazards and even wrote it out on my bill, but I think it was more important to him to have heat when he got out of the shower.

 

PROTECTION AGAINST ELECTROCUTION

GFCI protected electrical outlets are required in basements, bathrooms, garages, outdoors, for service outlets, in kitchens, for swimming pools, and for appliances such for equipment such as air conditioning, electric clothes dryers, and electric stoves.

You can protect yourself from electrical shock and electrocution by following some common sense guidelines.  When working or playing outdoors and using electricity be sure everything is plugged into GFCI receptacles.  GFCI receptacles and circuit breakers are designed to shut off power if there is a current imbalance of more than 5 milliamperes.  They are designed to save lives.

If you work outdoors on a regular basis using power tools you should get a portable GFCI.  A portable GFCI is OSHA approved and actually has one additional protection factor that regular GFCI outlets do not have.  Portable GFCI’s have lost neutral protection.  That is, if the portable GFCI device senses that the neutral connection to it is gone, it will shut down.  A standard GFCI electrical receptacle does not do that nor does a GFCI circuit breaker.

When shopping for a portable GFCI make sure the labeling says OSHA approved or open neutral protection.  I have noticed that there are a few on the market that don’t have such labeling.  Buyer beware.  You can see the model portable GFCI that I own on my Be Safe When Working at Home Post.

Wear shoes when working outside using electrical tools and equipment.

The same applies when working in the garage or basement.  The concrete floor is a very good electrical ground surface.  Always wear shoes when working with electricity on concrete floors.

The 2020 National Electrical Code has an expansion of GFCI requirements for such things as outdoor central air conditioning units, electric clothes dryers, and electric stoves.  Some applicable articles are 210.8(A)(1) to (11), 210.63(A), 210.63(B).  I read some stories how small kids were playing and somehow got behind faulty appliances and were electrocuted.

GFCI’s do offer good protection against shocks and electrocutions, but there is no guarantee in all circumstances that tragedy will be averted.  Use common sense and keep electricity away from water, pets, and kids.

ELECTRICAL HAZARDS WHILE BOATING

I have been reading more and more articles about electric shock hazards from boats.  People have received shocks or have been electrocuted from swimming around boats docked in the water.  Some of the causes have been traced back to faulty wiring on boats, some of which was modified by the boat owner.  All electrical outlets for boat docks must be GFCI protected.  Read article 555 in the 2020 National Electrical Code.

Do not go swimming in the water where boats are located.  There is no way to know if an electrical hazard exists without going in the water.

ELECTRICAL HAZARDS FROM SWIMMING POOLS

In my state an electrical inspection and certification of commercial pools is required every five years.  I have done a few of these and have always found a problem, though usually minor and easily correctable.  However there is no such requirement for homeowner owned pools.  Many home pools are serviced by pool companies, but they are not qualified to determine electrical code violations or safety issues.

If you own a pool I strongly suggest that you have a licensed electrician do an inspection and testing of the pool grounding and bonding and also of the GFCI circuit breakers for the pool equipment.  Have it done every few years.

The same electrical hazards could also exist in hot tubs, water fountains, and homemade ponds.  Their circuits should be GFCI protected as well.

When working on electrical wiring, it is important to shut the power off.  However just because the circuit breaker is off does not mean that all current flow has stopped.  Multi-wire circuits are now required to have a two pole or three pole circuit breaker.  Several years ago this was not a requirement.  Consequently there are are many homes wired with multi-wire circuits that do not have a multi-pole circuit breaker.

This is important because on a multiwire circuit, the neutral conductor is shared between circuits.  So if one circuit is off, current can still be flowing on the neutral from the other circuit.

I was doing some repairs in a home for a do-it-yourselfer who was preparing to sell his home.  I had removed the circuit breaker cover and saw no multi-wire for the circuit I was working on.  I shut off the breaker and proceeded to disconnect the wiring when I got zapped on the neutral conductor.

I had the homeowner shut off each circuit breaker until the neutral current went away.  The circuit breaker was located in another circuit breaker panel.  When the homeowner was doing his own wiring he needed a neutral so he tapped into the nearest available junction box to use the neutral only.  Very dangerous!

Read some of my other other safety tips here.