Space Heater Safety: The Rules That Prevent Fires

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A plug-in heater is the fastest way to warm one cold room on a damp Bay Area night, and it is also the heating appliance most likely to kill someone. Used with a few firm rules it is perfectly reasonable. Used as a permanent fix for a furnace that has quietly stopped keeping up, it is a risk you are taking every night.

This guide is part of our Bay Area Winter Heating Help Center. It covers the numbers, the rules that actually prevent fires, which kind of heater to pick, and how to tell when the space heater is a symptom of a heating problem that should be fixed.

Why the rules matter: the numbers

Space heaters are a small share of heating equipment but a large share of the harm. The National Fire Protection Association reports that space heaters account for about one-third of home heating fires but nearly nine out of ten of the deaths (NFPA). The U.S. Fire Administration puts it more sharply: portable heater fires were only 3% of home heating fires in 2017 to 2019 but 41% of fatal heating fires (USFA). The Consumer Product Safety Commission counts about 1,600 portable heater fires a year, with an average of 70 deaths and 160 injuries a year from 2019 to 2021 (CPSC). NFPA also notes that nearly half of heating equipment fires happen from December through February, exactly when Bay Area homes switch the heat on.

Our read on why, after decades in Bay Area homes: a space heater sits right where people are, next to beds, sofas and piles of laundry, and it is easy to forget one is on.

The rules that prevent fires

• Three feet of clear space, all around. Keep anything that can burn, like bedding, clothing and curtains, at least 3 feet from the heater (USFA). CPSC adds furniture to the list (CPSC). Walk around the heater and check the back and sides, not just the front. Kids' toys, pet beds, a dropped blanket and the dog's tail all count.
• Straight into a wall outlet. CPSC says to always plug an electric space heater directly into a wall outlet, never into an extension cord or power strip (CPSC). USFA adds: do not plug anything else into the same circuit (USFA). On high, a typical plug-in heater draws close to what an ordinary bedroom circuit can carry, so a phone charger and a TV on the same circuit can be enough to overheat a tired outlet in an older house.
• Off when you sleep or leave the room. "Never leave the heater operating while unattended or while you are sleeping" (CPSC). Warm the bedroom before bed, then switch the heater off and unplug it. Use extra blankets for the rest of the night.
• Tip-over shutoff and a lab listing. USFA says to make sure the heater has an automatic shut-off if it tips over and has been tested by a recognized testing laboratory (USFA). In practice, look for a mark such as UL or ETL on the label.
• Hot cord or plug means stop. If the cord or plug is hot, disconnect the heater (CPSC). A plug that is warm, discolored or loose in the outlet, or an outlet faceplate that is warm to the touch, means that outlet needs an electrician before anything else goes in it.
• Check for recalls. CPSC suggests checking SaferProducts.gov to see whether your model has been recalled, especially for a heater bought secondhand.
• A hard, level floor. Set it on the floor, not a table, chair or bed, and away from foot traffic and doorways where someone can knock it over in the dark.
• Keep it dry. Do not use a heater in a bathroom or laundry area unless the manual says the model is designed for it, and never touch one with wet hands.
• Working smoke alarms. Test them before the first cold night. A heater in a bedroom deserves a working alarm in the hallway outside it.

Choosing a heater

No heater type is fire-proof. Each one is safer or riskier depending on where you put it.

For rentals, California's housing regulations are explicit: "No unvented fuel burning heaters shall be permitted" (25 CCR 34). A home with any fuel-burning appliance, a fireplace or an attached garage also needs a carbon monoxide alarm under state law (Health and Safety Code 17926); our gas smell and carbon monoxide guide covers where to put them.

Things that are never a heater

When the furnace dies on a cold night it is tempting to improvise. Don't. The CDC's advice is plain: "Don't heat home with gas oven" (CDC). An open oven door, a stovetop burner left on, a charcoal or gas grill brought inside or into the garage, and a camp stove all burn fuel in your living space and can fill it with carbon monoxide. A hair dryer or a clothes iron left running is a fire waiting to happen. If you have no heat, layers, a warm room with the door closed and one properly used electric heater are safer than any of these.

When the space heater is telling you something

If you only reach for the heater a few evenings a year, fine. If one runs in the same room every night, your central heating is sending a message:

• One room is always cold. Usually a duct problem (a crushed or disconnected run in the attic or crawlspace), a missing return, poor insulation or a room added onto the house after the original system was sized. Our guide to cold rooms and uneven heating walks through the checks.
• The whole house is cold. The furnace or heat pump is not keeping up or not running at all. Start with the no-heat checklist and do not let a space heater become the long-term plan.
• A garage conversion or addition was never connected to the heat. A permanently installed ductless mini-split is the proper fix: it heats and cools, and it is far more efficient than electric resistance heat. See what a mini-split installation involves in the Bay Area.
• Breakers trip when the heater runs. The circuit is overloaded or has a wiring fault. Stop using that outlet for the heater and have an electrician look at it.

How we fix the problem behind the heater

When you call Cool Aid about a room that needs a space heater, we look at the system that should be heating it: supply and return airflow at the register, the duct run in the attic or crawlspace, the furnace's temperature rise and filter, and whether the room was ever part of the original design. Sometimes the fix is a reconnected duct or a new return; sometimes it is a ductless head for an addition. Either way we explain what we found before any work starts, and every repair carries our 1-year parts and labor warranty. Our residential HVAC repair page covers the rest of what we do.

Get the cold room fixed properly

Frequently asked questions

Written and reviewed by Jim McKinny, owner of Cool Aid Air Conditioning & Refrigeration — California C-20 and C-38 licensed, EPA Universal certified, second generation of a family business serving the Bay Area since 1966. Every job we complete is backed by our 1-year parts & labor warranty.