Extension Cord Safety: 8 Mistakes That Cause Fires
Extension cords cause 3,300 house fires every year. Most are preventable. Here are the 8 most dangerous mistakes people make and how to use extension cords safely.
The Scope of the Problem
According to the US Consumer Product Safety Commission, extension cords cause approximately 3,300 residential fires every year, resulting in 50 deaths and over 270 injuries annually. The National Fire Protection Association reports that extension cord fires cause $117 million in property damage each year. These fires are almost entirely preventable because they are caused by misuse rather than manufacturing defects. Understanding these 8 common mistakes can literally save your home and your life.
Mistake 1: Using Indoor Cords Outdoors
Indoor extension cords have thinner insulation that degrades when exposed to moisture, sunlight, and temperature extremes. Outdoor-rated extension cords have thicker, weather-resistant insulation and waterproof connections. Using an indoor cord outdoors, especially in wet conditions, creates a shock and fire hazard. Look for cords marked with a W in the wire type designation, which indicates outdoor or wet-location rating. For example, SJTW is an outdoor-rated cord while SJT is indoor only.
Mistake 2: Daisy-Chaining Multiple Cords
Plugging one extension cord into another to extend the reach is called daisy-chaining, and it is a major fire hazard. Each additional connection adds resistance, which generates heat. The combined length also causes voltage drop, making appliances work harder and draw more current. This combination of extra heat and higher current can ignite the cord insulation. If you need to reach further, buy a single longer cord rated for your needs rather than chaining two shorter cords together. Extension cords are available in lengths up to 100 feet.
Mistake 3: Running Cords Under Rugs or Furniture
An extension cord generates heat during normal use, and this heat must dissipate into the surrounding air. When a cord is trapped under a rug, carpet, cushion, or furniture, the heat builds up because it has nowhere to go. Over time, this can deteriorate the insulation and ignite the cord or the material trapping it. The same principle applies to coiling excess cord length into a tight bundle. Always run cords along walls where they are visible and in open air. Never staple or nail a cord to a wall or baseboard because driving a fastener through the insulation creates a short circuit risk.
Mistake 4: Using Extension Cords as Permanent Wiring
Extension cords are designed for temporary use only. They are not a substitute for permanent electrical wiring. If you need an outlet where there is not one, hire an electrician to install one. The cost of adding an outlet ($150 to $300) is far less than the cost of a house fire. The National Electrical Code prohibits using extension cords as a substitute for permanent wiring. If you find yourself relying on extension cords for everyday appliances like refrigerators, space heaters, or window air conditioners, you need additional outlets or circuits installed properly.
Mistake 5: Overloading the Cord
Every extension cord has an amperage rating based on its wire gauge. A standard household 16-gauge cord is rated for 10 to 13 amps. Plugging in appliances that draw more current than the cord is rated for causes the wire to overheat. Space heaters (12 to 15 amps), window AC units (7 to 15 amps), and microwaves (8 to 15 amps) should never be plugged into a standard extension cord. These high-draw appliances should always be plugged directly into a wall outlet on a properly sized circuit. If you must use an extension cord for a high-draw appliance temporarily, use a heavy-duty cord rated for 15 amps (14-gauge or heavier).
Mistakes 6, 7, and 8: Damaged Cords, Wrong Polarity, and Ungrounded
Mistake 6: Never use a cord with a cracked, frayed, or damaged outer jacket. Exposed wiring is a direct shock and fire hazard. Replace damaged cords immediately. Mistake 7: Never cut or modify the prongs on a plug to fit an outlet. The third prong is a safety ground that protects you from shock if the appliance develops an internal fault. Removing it eliminates this protection. If your outlets only accept two-prong plugs, have an electrician install grounded three-prong outlets. Mistake 8: Never use an ungrounded adapter (cheater plug) to connect a three-prong plug to a two-prong outlet. These adapters are technically legal only when the adapter ground tab is properly connected to the outlet cover plate screw on a grounded metal box, which is rarely done correctly.
Pro Tips
Frequently Asked Questions
Can I plug a space heater into an extension cord?
No. Space heaters draw 12 to 15 amps, which exceeds the rating of most extension cords. Always plug space heaters directly into a wall outlet on a dedicated circuit. Using an extension cord with a space heater is one of the leading causes of residential electrical fires.
How do I know what gauge extension cord I need?
The gauge number indicates wire thickness. Lower numbers mean thicker wire and higher capacity. For lamps and phone chargers, 16-gauge is fine. For power tools and larger appliances, use 14-gauge or 12-gauge. The cord packaging lists the amperage rating, which should exceed the amperage draw of whatever you plug into it.
How long can I safely use an extension cord?
Extension cords are designed for temporary use only. The National Electrical Code does not specify an exact time limit, but the intent is that they should not be used as permanent wiring. If you have been using the same extension cord in the same location for more than 30 days, you should have a permanent outlet installed instead.
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