Run over, walked on, crimped in windows and doors, left out in sun and storm alike, strung together, bent, yanked and strung across rooms and under carpets, strewn across wet grass and through holes in walls, taped up and snarled in tangles that would give a sailor nightmares. Used in the office, in the lab and in the field, taken for granted until you need one. What are we talking about? Electrical cords, one of the most indispensable tools we use today but often with little consideration and used in a fashion that could have disastrous results.

According to the Consumer Product Safety Commission, electrical cords and plugs were involved in about 7,100 fires resulting in 120 deaths in 1996. In 1997 more than 12,000 people were treated for electrical shocks and burns. About 2500 of them were treated for injuries stemming from extension cords. With a little care and some precautions these conveyors of power can be used safely.

The use of cords indoors and outside usually stem from different needs. We must caution up front, that if you have more than a few extension cords powering equipment in your lab, it is probably time to call an electrician to install additional strategically placed outlets or rearrange equipment. Likewise, if you have any cords running through walls, up through the ceiling and down somewhere else, an electrician is definitely required. Extension cords should only be used when necessary and only for temporary use. You should always plug equipment directly into a permanent outlet when possible. Where this is not possible however, you should begin by selecting the right cord for the job.

Always use the three prong type of cord approved for indoor and outdoor use. The cord should have a certification label from an independent testing lab such as UL (Underwriters Laboratories) or ETL (Electrical Testing Laboratories) on the package and attached to the cord near the plug.

The amount of current a cord can handle will depend on the diameter of the conductors (copper part of wire). Wires that contain more copper can safely handle more power. The wire size is measured by the gauge of the wire. You will usually find numbers like 16, 14 or 12 gauge on extension cord package and the cord itself. Now this is one of those confusing issues. You would think that a 16 gauge wire is bigger than a 12 gauge wire, but it’s not! As the number gets smaller, the thickness of the conductor gets bigger! A 12 gauge wire can safely carry much more power than a 16 gauge wire. Compare the capacity on the label to the intended load.

Always use the shortest extension cord possible to minimize risk of damage to the cord and reduce electrical resistance across the length of the cord.
You have picked out your cord; is it safe to use? Extension cords, by the nature of their length and conditions of use, are much more prone to damage than other types of wiring. It is important to check the total length of the cord for damage before putting it in use.

One should start by looking at the ends of the cords. The male end – the end with the three prongs that fit into an electrical outlet – is the one that is most prone to damage. The two flat power-conducting prongs are subject to bending, while the round prong (often called the ground pin), can be broken off. Without the ground pin there is no path to ground through the wires; potentially a very dangerous situation.

Outdoor use extension cords and many equipment cords have a tough outer layer designed to protect the inner wires. If the outer jacket is damaged, the softer inner insulation around the wires can easily become damaged. Does this mean whip out the tape to repair it? No, no, no, damage to an extension cord jacket, or any cord, for that matter– should never be fixed by wrapping it with tape. Even electrical tape, does not have sufficient strength or abrasion resistance to make a permanent repair as required by OSHA. A taped-up extension or power cord to a piece of equipment is an easy OSHA citation and would make the inspector’s day.