At the University of Idaho, 30 percent of the safety discrepancies noted during the annual building safety inspections are of an electrical nature, including extension cords, daisy-chains, multi-plug adapters and homemade extension boxes.
Data obtained from the Bureau of Labor Statistics' Annual Survey indicate that approximately 10 percent of all occupational fatalities are due to electrocutions. The U.S. Consumer Product Safety Commission (CPSC) estimates that approximately 2,200 injuries associated with extension cords are treated annually in hospital emergency departments. The CPSC also estimates about 5,000 residential fires originate from extension cords each year, killing 85 persons and injuring some 230 others.
Extension cords are for temporary use only, and not intended to be used as a substitute for fixed wiring in a structure. They provide power to portable appliances by extending the power supply cord of electrical equipment and should be marked with a current rating sufficient for the load of the connected equipment. Grounded extension cords are required to have the grounding plug intact; the grounding prong of an extension cord should never be bypassed or broken off. Extension cords should not be attached to building surfaces. Attachment points subject the cord to weathering, damage from fasteners, mechanical abuse and strain or repeated flexing. Extension cords must be disconnected from the power supply when not in use.
Relocatable power taps (power strips) are considered extensions of the branch circuit. Therefore, they are intended to plug directly into a branch-circuit outlet, not another relocatable power tap, multi-plug adaptor or an extension cord. Potential overheating is one concern when relocatable power taps are used in a series arrangement (daisy-chaining). Other considerations in a series-connected arrangement include the reaction between over-current protective devices on relocatable power taps, increased voltage drop, potential tripping hazards and an increased likelihood that additional available outlets may lead to an overload. Only circuit-protected relocatable power taps are allowed in university buildings.
Flexible cords may not be placed under carpet, through holes in walls, floors or ceilings, or through openings in partitions with sharp edges. These are conditions that can result in damage to the insulation or conductors, and increase the likelihood of an electric shock or fire. Multi-plug adapters and homemade extension boxes are not allowed in university buildings.