Space Heater Safety: How to Use One Without the Risk

This guide is for anyone using a portable space heater this winter, or shopping for one for a bedroom, office or drafty room.

A space heater can make one cold room comfortable without heating the whole house. It also puts a lot of heat in one small spot, often next to a bed, a couch or curtains. That’s why a few habits matter more than the brand you buy. Here are the rules federal fire agencies give, what to look for in a safer heater, and answers to the questions people ask most: overnight use, extension cords and propane heaters indoors.

Why space heaters need extra care

The U.S. Fire Administration (USFA) estimates that heating caused 32,200 home fires in 2021, with 190 deaths, 625 injuries and $442 million in property loss.¹ Portable heaters are a small part of that, but a deadly one: from 2017 to 2019 they were involved in only 3% of home heating fires, yet in 41% of fatal heating fires.¹

Our reading of those numbers: space heater fires are rare, but when they happen they tend to start close to people, often while they’re asleep, next to bedding or furniture.

The space heater safety rules

1. Keep a 3-foot zone. The USFA and Ready.gov both say to keep anything that can burn at least 3 feet away from a space heater.¹³ That includes beds, blankets, curtains, sofas, clothes, paper and holiday decorations.
2. Turn it off when you leave the room or go to bed.¹
3. Plug it straight into a wall outlet. The USFA’s heating safety graphic warns against using an extension cord with a space heater.¹
4. Choose a heater with safety features. Ready.gov recommends heaters that are UL-listed, have a thermostat, and shut off automatically if they tip over.³
5. Never use your oven to heat your home.¹ The CDC gives the same warning for gas ovens, because of carbon monoxide.⁴

Our advice to add to those:

• Put the heater on a hard, level floor, never on a rug, a bed, a chair or a table it could fall from.
• Keep children and pets out of the 3-foot zone.
• Check the cord and plug before each use. If the plug or outlet feels hot, stop using it.
• Don’t dry clothes or shoes on or over a heater.
• Keep it out of bathrooms and wet areas unless the maker says it’s made for them.

Can you leave a space heater on overnight?

The USFA’s answer is to turn space heaters off when you go to bed.¹ Even heaters sold as “safe for overnight use” are still a heat source a few feet from your bed while you can’t watch it.

Our advice for a cold bedroom:

• Warm the room before bed, then switch the heater off when you get in.
• Use extra blankets, flannel sheets or a warmer sleepwear layer instead of all-night heat.
• If you use a heater with a timer, set it to shut off soon after you fall asleep rather than run all night.

Can you plug a space heater into an extension cord?

The USFA says not to.¹ Our explanation: a space heater pulls a lot of current for hours at a time. Most household extension cords and power strips aren’t built for that steady load, so they can overheat at the plug or along the cord, often where you can’t see it, under a rug or behind furniture.

Our advice: if the heater’s cord doesn’t reach an outlet, move the heater, not the outlet. Avoid plugging other high-power devices into the same outlet at the same time.

What makes a space heater safer

These are our shopping checks, not a ranking. The first three line up with Ready.gov’s advice.³

As for the “safest type of space heater,” our advice is to focus on features and where you’ll use it, not on heating technology. Electric heaters don’t produce carbon monoxide, which makes them the usual choice for bedrooms, offices and nurseries. Oil-filled radiator-style heaters have no exposed glowing element, which helps around pets, though the housing still gets hot.

Propane and kerosene heaters indoors

Heaters that burn propane, kerosene or another fuel produce carbon monoxide (CO), a gas you can’t see or smell.

• CPSC says never use fuel-burning portable heaters or lanterns while sleeping in enclosed areas such as tents, campers and vehicles, and that the risk is higher at high altitude.²
• For kerosene heaters, CPSC says to use only water-clear 1-K grade kerosene, and never gasoline.²
• The CDC recommends a battery-operated or battery-backup CO detector near every sleeping area.⁴

Our advice on “indoor safe” propane heaters: use only a heater the maker specifically labels for indoor use, follow its ventilation instructions exactly, never run it while you sleep, and have working CO alarms before you light it. If you’re choosing between fuel and electric for a room where people sleep, choose electric. See our carbon monoxide detector placement guide.

CPSC lists the symptoms of CO poisoning as headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion, and notes they are easily mistaken for a cold or the flu.² If they appear while a fuel-burning heater is running, get everyone outside and call 911.

Space heaters around kids and pets

Our advice:

• Choose a model with a cool-touch housing and tip-over shutoff.
• Place it where it can’t be bumped by a running dog or pulled over by its cord.
• Don’t leave a heater running in a room with a pet when no one is home.
• In a nursery, keep the heater well outside the 3-foot zone around the crib and turn it off once the room is warm.

The rest of your heating system

The USFA also says to have chimneys and heating equipment inspected by a qualified professional every year.¹ A space heater is often a sign the main system isn’t keeping up, so it’s worth asking the technician about drafts and cold rooms at the same visit.

Space heater checklist

• Three feet of clear space all around.
• Plugged straight into the wall, no extension cords.
• Tip-over shutoff, thermostat and a lab certification mark.
• Off when you leave the room or go to bed.
• Fuel-burning heater? Labeled for indoor use, never while sleeping, CO alarms working.
• Working smoke alarms on every level.