The core extension cord safety tips are: use cords only temporarily, choose one rated for the job and for indoor or outdoor use, never plug cords into each other, keep them out from under rugs and out of doorways, throw out damaged cords, and never run a space heater or major appliance on one.
ESFI reports that roughly 3,300 home fires start in extension cords each year, killing 50 people and injuring 270 more. The tips below target the habits ESFI, NFPA, USFA and CPSC warn about most: overloading, covering cords so heat cannot escape, and using damaged cords.
NFPA says extension cords are intended for temporary use. ESFI goes further: do not substitute extension cords for permanent wiring. If you find yourself relying on cords in the same spots month after month, that is a sign the room needs more outlets, and ESFI suggests having them installed where you need them. That is a job for a licensed electrician.
Look for a testing lab mark. ESFI says to buy only cords approved by an independent testing laboratory.
Match indoor or outdoor use. Cords should be rated for their intended use, indoors or outdoors (ESFI). An indoor cord does not belong outside.
Match the power. The cord must be able to supply the power the device needs (ESFI). Check the cord's rating against the device's label, and if you are not sure, ask at the hardware store.
Retire thin old cords. CPSC's home checklist says to discard older extension cords that use small 18 gauge wires.
Respect the third prong. Never force a three-prong plug into a two-slot outlet, and never cut off the ground pin to make it fit (USFA, ESFI).
Garage and yard tools: OSHA's job-site rules give a useful benchmark. They call for flexible cords rated for hard or extra-hard use, with the rating marked about every foot along the cord, and 3-wire extension cords that can be grounded.
Not under rugs or carpets. USFA says to avoid putting cords where they can be damaged or pinched, like under a rug. ESFI explains that covered cords cannot release heat, which creates a fire risk.
Not through walls, doorways, ceilings or floors (ESFI). NFPA also says to check that cords are not running across doorways.
Not nailed or stapled to walls or baseboards (ESFI). OSHA notes cords can be damaged by door or window edges, staples and fastenings, rubbing against other materials, or simply aging.
Not across walkways. CPSC's checklist says cords should be out of the flow of foot traffic, since they are a tripping hazard. This matters most in an older parent's home.
Outdoors, not in snow or water. Keep outdoor cords clear of snow and standing water (ESFI).
Do not plug extension cords into one another (ESFI).
Do not overload extension cords, power strips or outlets (ESFI, USFA, CPSC).
Use power strips that have internal overload protection (USFA).
Plug only one heat-producing appliance, such as a coffee maker, toaster or space heater, into an outlet at a time (NFPA).
ESFI says not to use an extension cord or power strip with heaters or fans, because the cord can overheat and cause a fire. NFPA and USFA say major appliances such as refrigerators, stoves, washers and dryers should plug straight into a wall outlet, and USFA warns that an extension cord used with one can overheat and start a fire. Our space heater safety guide covers the rest of the heater rules.
ESFI says to inspect cords before each use. Look for:
Cracked or frayed sockets
Loose or bare wires
Loose connections
Staple or nail holes, cracking or fraying along the cord (CPSC)
USFA says to replace worn, old or damaged extension cords right away. OSHA explains why: once the conductors inside are exposed, the cord can cause shock, burns or fire. Do not tape it up and keep using it.
This is an example routine based on the guidance above, not an official checklist. Walk the house once a season:
List every extension cord in use. Could any of them be replaced by a nearby wall outlet?
Unplug and look over each cord for damage. Throw out any that fail.
Check nothing covers a cord: no rugs, furniture legs or piles of laundry.
Make sure no heater, fan, refrigerator, washer, dryer or stove is on a cord or power strip.
Look for cords plugged into other cords and remove the chain.
Move cords out of walkways and doorways.
If a cord, plug or power strip is smoking, melting or on fire, get everyone out, stay out and call 911 from outside. If a cord or plug feels hot, stop using it, unplug it only if that is safe, and replace it. If the outlet itself is hot or scorched, call a licensed electrician.
It is best not to. ESFI says not to plug extension cords into one another, and USFA warns against overloading power strips. If you need more outlets, have an electrician add them.
No. USFA says to keep cords out from under carpets and rugs, and ESFI explains that covered cords cannot release heat.
No. ESFI says cords must be rated for their intended use, indoors or outdoors. Use a cord rated for outdoor use and keep it out of snow and standing water.
There is no set number of hours, but NFPA says extension cords are for temporary use. If one has become permanent, have an outlet added instead.
RoomMend: Safer Home Plans is a free iPhone and iPad app, with an optional RoomMend Plus upgrade, that sets up a room-by-room safety checklist for your home or a parent's. If you find a cord under a rug or a heater on a power strip, you can log it in about three taps with an optional photo and a timeframe, mark it fixed, and get a reminder to look again after 30 days. Everything stays on your device and it works offline, but it is not a safety certification, so the rules above come first.
Get RoomMend free on the App Store
Reaching to Safety: Use Extension Cords Properly (Electrical Safety Foundation International)
Appliance and Electrical Fire Safety (U.S. Fire Administration)