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Are Space Heaters Safe To Leave On All Night?

No, space heaters are not safe.
Are Space Heaters Safe To Leave On All Night?
Tom Greenspan
Updated 
December 21, 2022

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We are heading into that time of year when we are thinking about pulling our space heaters out of the garage and storage to provide a little heat on those upcoming chilly days. However, there is a burning question that needs to be discussed, and that question is, are space heaters safe to leave on through the night?

Before we go further, it is worth mentioning that statistics state that 85% of all deaths from fire were directly correlated to space heaters. It's a sobering thought as we shake off the dust from our stored space heaters.

In this article, we will address frequently asked questions, and more so, you have the facts about space heaters that are left switched on overnight in your home.

Let’s get into it.

What to look out for when buying a space heater?

There are certain things you need to look for when buying a new space heater that will ensure its safe for use in your home, and they are:

  • Check the label. The heater should be listed by a qualified testing laboratory. Look for the UL mark from Underwriters Laboratories, the ETL label from Intertek, or certification from CSA International.
  • Be smart. Look for a heater with an intelligent sensor that automatically shuts off the unit when it overheats or is tipped over.
  • Electric only. Electric heaters are the only type of space heaters that are safe to use indoors without venting, says the DoE.

Setting up a space heater

  • Keep away from water and wet floors. Never touch an electric space heater with wet hands.
  • Be smart. Your space heater is designed to be floor mounted only. Never place a heater on furniture or cover it with anything; it will catch fire.
  • Give the heater space, and keep your space heater clear of drapes, bedding, and furniture. It must have a minimum clear perimeter of three feet front, back and sides.
  • Trip hazard. If the cord is exposed, place it under a rug to prevent tripping. Be sure not to place the space heater in a high foot traffic area where tripping could be a hazard.
  • Don't use a power strip or extension cord. Space heaters draw a lot of electricity, and a power strip may not be rated for the power requirement making the power strip a fire hazard.
  • Power heaters are potentially dangerous when used in a garage where flammable liquids are kept.

What types of space heaters are available?

There are many variants of space heaters, but they vary in safety features when considering if you can use a safety heater through the night.

Here is a brief list of the different types of space heaters for domestic use:

  • Ceramic space heaters are small plastic space heaters frequently used to add heat to a small room. The elements are ceramic and, if maintained, can be reliable.
  • Convective ceramic heaters. They are small and efficient. Most of you will be familiar with this type of heater. It has a fan and blows warm air into the room.
  • Fan space heaters. It works by heating a coil and blowing air across the coil, and they are known to cause allergies due to air and dust circulation.
  • Infrared heaters are better for your health because, unlike most heaters, they don’t dry out the air. They don’t reduce oxygen in the room. They don’t reduce the amount of oxygen in the room. These heaters don’t create toxic gasses and other fumes.

You won’t waste your money heating the room because infrared heaters focus only on heating the objects near them. These heaters work as soon as you turn them on, so there is no need to preheat them. 

These are just a few types of space heaters available for domestic use.

How long can space heaters be left on?

 Maximum 10 hours. It depends on the circumstances and other factors such as the size of the room and does the room have adequate ventilation.

When using a space heater, you need to make some preliminary checks before you use it, such as:

  • Is the cord in good shape? Loose and frayed cords are potential hazards for electrocution and fire, so if your space heater has a cord that looks like it has seen better days, don't use it.
  • Does your space heater have at least 3 feet of free space around it so any convection heat can be dissipated into the air and not your furnishings that could be a fire hazard?
  • Can you plug your space heater directly into a wall power outlet? Using a power strip is dangerous and could cause the power strip to become hot and burst into flames.
  • Do you have a carbon monoxide alarm fitted in the room where you use the space heater? Space heaters emit carbon dioxide, and it is a silent killer that immobilizes your body while your brain usually functions until you are overcome with fumes and expire.
  • Do you have a smoke alarm in the room where you use the space heater? More people die from smoke inhalation than actual burns. A smoke detector is essential when using a space heater.

Don't use the space heater continually. Use it in blocks of time, say 90 minutes and then switch it off for 30 minutes. This will prevent a previously used space heater from overheating.

Some radiant heaters perform better and can be left on for longer periods, such as in an oil-filled space heater. Oil-filled space heaters use a resistive coil to generate heat, but the coil is immersed in a special oil and then enclosed. The coil transfers heat to the oil.

If this heater is going to be used for extended periods of time, there needs to be sufficient space surrounding the heater. A minimum of 3 feet is suggested but more if possible.

How do I know if my space heater is safe?

If you are buying a new space heater, look for a space heater that has these features:

  • Tip over switch: This sensor will cut off the power to the heater element should the space heater reach a certain angle where it could topple and cause a fire.
  • Overheat sensor. Space heaters should be fitted with an overheat sensor. Clearly, if the pace heater gets hotter than its design parameters, the safety device will cut power to the heater element rendering the space heater inoperable.

If you are bringing a space heater out of storage, you will need to run visual safety checks, such as checking the power cord for integrity. Mice like to nibble on power cords, so be very thorough with your visual inspection.

When you plug your space heater in directly from coming out of storage, expect it to smoke, so be sure to have the windows open and good ventilation. The smoke will be from accumulated dust around the heating elements. Generally, it burns off quickly, and it's not a problem.

There is a problem if there is heavy smoke, so you need to isolate the power supply without delay. Any sparks, pops, and bangs are not usual, so it may be time to upgrade your space heater to one with all the safety features built into it.

Is leaving a space heater on a fire hazard?

Yes. Portable heaters are a significant contributor to fires. Space heaters are high-wattage appliances that can easily cause household materials to combust. Space heaters are a fire hazard; you should use great care when using this domestic heater.

In your average living room, you have combustible items such as drapes, a sofa, soft furnishings, and clothes and paper.  Should ignition of any of these materials occur, you could have a significant fire threatening your life and home.

How do most space heater fires start?

There is more than one way for your space heater to cause a fire. A space heater draws a lot of currents, sending the heating elements above 500℉, which will cause a power strip to melt and burst into flames. Many power strips and extension cords are not rated sufficiently to use a space heater.

The consequences are self-evident if such an incident should occur. Make sure you plug your space heaters directly into a fused power outlet on the wall.

And then there is this:

Overheating of older space heaters without the correct safety features is commonplace. When combined with improper and somewhat thoughtless use, the inevitable will cost the homeowner considerably.

Placing a space heater in a room without the recommended three feet perimeter so the heater can draw in air efficiently is a foolhardy practice.

Is your fire retardant furniture going to protect you? Think again.

TB 117-2013 (the mandatory standard flame retardant) required the foam inside furniture to withstand a small open flame for 12 seconds. However, in a real fire, the cover fabric will ignite first, leading to a large flame that will quickly ignite the foam, even if it contains flame retardants. Furniture with and without flame retardants burns similarly.

The sobering facts about flame retardants should make you focus on space heaters and realize just how dangerous these home appliances can be if misused and abused.

Is it safe to leave a space heater plugged in?

No. In 2021 there were 500 fatalities caused by space heaters in the US. This frightening statistic should galvanize your thoughts and actions regarding the safety of space heaters.

No, one expects you to be cold during the winter months, but what is expected is a modicum of common sense and, in some ways, compliance with instructions. If most of the fatalities were caused by disregarding instructions, that would be a sorry state of affairs.

If you are using an electric heater, you will not have to worry about carbon monoxide poisoning. 

If your space heater is working fine, it has an excellent power cord, and it's not smoking every time it is switched on, the fire hazard is evident.

Place your space heater in a place that is clear of soft furnishings and combustible materials. Now in a larger room, you may not feel the heat as the heater is not big enough to cope with an ample space. Don't be tempted to draw the space heater closer so you can toast your toes.

What is the safest heater for a bedroom?

Only one space heater is suitable for a bedroom: a self-enclosed oil heater, also known as a radiant heater. It is a radiator with no fans to force air around the bedroom, but it is adequate for heating a bedroom.

Radiant space heaters are stylish and give off plenty of heat. They are transportable and can be used in any room in the house to supplement the room's heat.

They will typically have a built-in thermostat that will trip in and out with the bedroom's temperature, making them safer than other space heaters that use resistive wires to generate heat which is then distributed in the room via the built-in fan.

Can you leave a radiant heater on through the night?

Yes. If you set the thermostat to a reasonable heat of 68℉ for the bedroom and the bedroom is not drafty, the radiant space heater will trip in and out through the night, maintaining the bedroom temperature.

Can you dry clothes against a radiant space heater?

No. Use the radiant space heater for its purpose and stick to the rules to prevent fire hazards.

Should you leave your space heater plugged in day and night?

The best course of action might not be to leave your space heater plugged in. Long-term, it can end up being a waste of time and resources.

Because space heaters are made to heat a room rapidly, leaving one on all day will just waste energy. Additionally, you use more power and spend more money if you have many space heaters going at once.

According to the Department of Energy, shutting off your space heater while not in use can help you save up to 10% on your annual electricity bills.

Therefore, check your space heater before you go to work in the morning or before you go to bed at night.

Space heaters and small rooms

Death may arise from hyperthermia; overheating a small room can be extremely dangerous, even if there is no presence of carbon dioxide.

Space heaters should never be left on in a small area with newborns or persons with impaired physical, sensory, or mental skills.

For infants and the elderly, hyperthermia can be a rapid process, so great care and attention are needed in this scenario.

Can an electric space heater make you feel sick?

Yes. Electric heaters create warm air in the room they are being used. The very nature of an electric heater can raise health issues in certain people due to dry air conditions. Once the moisture content in the air has been diminished, several disorders can manifest.

Breathing dry air can affect the respiratory system, particularly in the elderly and infants. It is possible to see disorders such as bronchitis and asthma manifest. 

Sinusitis is a common ailment from the dry air causing blocked, stuffy noses, which can result in severe nose bleeds due to dry membranes.

To combat these ailments, you can use an old remedy of placing a bowl of clean water in the room. Of course, well away from the heater and power outlets.

Is it safe to palace a radiant heater on the carpet?

Yes. There is a caveat. Your space heater will need to be stable and not susceptible to being knocked over easily. The radiant heater will be fine on the carpet if it is stable.

Heat rises, so the floor beneath the radiant heater should not be hot to the touch.

Final thoughts

Space heaters should be used to supplement your principal heating supply during cold snaps or when the weather is just starting to turn through fall.

The only space heater you should consider leaving switched on overnight is the oil-filled radiant heater, and then you should stick to the fundamentals of using a space heater correctly, such as:

  • Keep away from water and wet floors. Never touch an electric space heater with wet hands.
  • Be smart. Your space heater is designed to be floor mounted only. Never place a heater on furniture or cover it with anything; it will catch fire.
  • Give the heater space, and keep your space heater clear of drapes, bedding, and furniture. It must have a minimum clear perimeter of three feet front, back and sides.
  • Trip hazard. If the cord is exposed, place it under a rug to prevent tripping. Be sure not to place the space heater in a high foot traffic area where tripping could be a hazard.
  • Don't use a power strip or extension cord. Space heaters draw a lot of electricity, and a power strip may not be rated for the power requirement making the power strip a fire hazard.