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Extension Cord Safety

January 6, 2012

Someone may have made you feel guilty about using an extension cord due to the threat of fire.  Are extension cords dangerous?  Like most things in life, the answer to that question depends on whether you use the extension cord properly or not.

According to the Consumer Product Safety Commission (CPSC) the number one hazard from extension cords has nothing to do with fire.  The biggest injury category from extension cords is trips and falls.  CPSC estimates 4,000 ER visits annually from tripping over extension cords.  They also report lots of child injuries from putting extension cords in their mouths. Keeping cords out of the way sounds like good advice.

Our experience tends to be fire, and extension cords can contribute to fires in several ways.

First of all is overloading a cord.  A specified diameter of copper wire will carry a specified amount of current before it overheats.  Use too much current through that small cord, and it can overheat, melt down and ignite household furnishings.  Make sure that the appliances hooked to the extension cord do not exceed the rating for the cord.  You can read labels on appliances to determine how many amps each appliance draws (some report watts which is amps x 120).  Add together the amperage rating of all appliances used on that cord and you can tell what size extension cord you need.  Today, extension cords either have the rating stamped on a plug, or a tag is affixed telling you what amperage it is rated to support.  Devices that produce heat (hair dryers, curling irons, portable heaters, etc) or power tools that do heavy work tend to be high-amperage items.  Ensure the cord can support the total amperage load you put on it and you should have no problems.

Damage to cords is a second concern.  Anytime you breach insulation in a cord, you’ve provided a point for current to travel out.  If current can travel from one wire to a person, they’ll get shocked.  If current can travel from the cord to a metal object, anyone who touches that object can get electrocuted, or the current can ground out creating heat and potentially a fire.  If current travels from one wire to another within the extension cord, you have a short circuit which will trip a breaker if everything works right, and can cause a fire if everything does not work right.  Keep cords where they will not be exposed to mechanical damage.  Check them over periodically and if they show any damage, replace them.  Pull plugs out of the socket by the plug, not the cord.  That ensures wires do not get pulled out of the plug and exposed.

A final problem is coiling electrical cords.  I know, coiled cords look much neater but there are some physics principles involved here that can start a fire.  Household alternating current sets up a weak magnetic field and collapses it 60 times every second.  Setting up and collapsing that magnetic field results in heat.  A single cord by itself won’t create enough heat to be a problem.  However, if you coil the cord so you have multiple strands running together, constructive interference increases the amount of heat generated.  Coil a cord enough times, and run enough current through it and you can create enough heat to ignite household furnishings.  I’ve fought two fires from extension cords that were coiled while in use.

Extension cords are tools for use with electrical appliances.  Any tool is safe if you use it correctly.  Just like a chainsaw, an extension cord that is used improperly can result in damage or injury.  If you’ve got questions about extension cords you can e-mail me at dbleeker@scfd9.org, or call 509-466-4602, or leave a comment on this site.

References

U.S. Consumer Product Safety Commission.  (n.d.).  Extension cords fact sheet.  Retrieved January 5, 2012, from http://www.cpsc.gov/cpscpub/pubs/16.html

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From → Fire Prevention

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