The National Electrical Safety Foundation (NESF) recommends you do not use extension cords, even industrial-strength varieties, as permanent additional outlets. When you use one temporarily, make sure it's rated for the equipment you plug into it. Never leave an unused extension cord plugged in since it conducts electricity regardless of whether there is something attached to it or not.

Get additional tips from the NESF by visiting its web site: www.nesf.org.