Is it true that heaters burn oxygen?

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There is concern that heaters may be dangerous to human health - they allegedly burn oxygen. We checked whether such fear is justified.

Russian speaking users services questions and answers are discussing reasons why a heater may decrease amount of oxygen or burn it, and are also asked question, is this even possible? Occurs a statement even on hospital websites: “The room needs to be ventilated more often, since most heaters burn oxygen.” Manufacturers electric heating devices release entire lines of devices that do not burn oxygen. Invited experts, in turn, share tips on how to choose such a heater, and they tell: “During the contact of air with a red-hot spiral, the notorious combustion of oxygen occurs.” In addition to heaters, in the combustion of oxygen accused and fan heaters.

Combustion is complicated process, including both physical and chemical phenomena. Chemically, combustion is an exothermic redox reaction where fuel reacts with an oxidizing agent (usually oxygen) to form new molecules (e.g. CO₂, H₂O) and release thermal energy. Physically, combustion is accompanied by the transfer of mass and energy, including through diffusion and convection, which affects the reaction rate. When the fuel is heated, its state of aggregation changes and flammable vapors are released, which facilitates further maintenance of the combustion process. 

burn can Substances capable of oxidation are predominantly organic compounds containing carbon and hydrogen, which release flammable vapors when heated. Metals, such as iron, do not themselves burn in the usual sense, but their small particles (dust, shavings) do. can actively oxidize with the release of heat. Some materials have a combustion temperature higher than the temperature of a normal flame, so under standard conditions they practically do not burn. 

The main oxidizing agent, without which most combustion processes are impossible, is oxygen. However, under some conditions reactions can be maintained, for example, with fluorine. The oxidizer accepts electrons from the fuel, releasing energy. Increasing oxygen concentration reduces temperature and ignition energy, accelerates combustion, increases the flame temperature. 

Since oxygen itself is an oxidizer and not a combustible substance, it does not burn on its own. For combustion to occur necessary three elements: a fuel source, oxygen (or other oxidizing agent) and an initiating energy source (fire, spark). In pure oxygen without fuel, combustion does not occur. Under the influence of, for example, ultraviolet radiation, the O molecule Maybe be converted to ozone (O), but this will not be considered combustion. 

In this case, there is a reaction called “oxygen combustion,” but it is impossible on Earth. Nuclear oxygen combustion is the process of thermonuclear fusion of elements in high-mass stars (usually more than 9–10 solar masses), where the core temperature reaches about 2 billion Kelvin, and the density is about 10 g/cm. In the body of a star, oxygen reacts with alpha particles (helium-4) to form heavier elements such as silicon, sulfur and argon. This is the late-burning stage in the evolution of massive stars before supernova formation. On Earth, reproducing such conditions is impossible, since extreme temperatures and densities are required to maintain nuclear fusion of oxygen.

Although the formulation “oxygen combustion” is not unscientific, it cannot have anything to do with the heater. And it is impossible to imagine that a household heater can create conditions in a room in which supernovae are formed. Therefore, we will further use the expression “consume oxygen.”

Household heaters work on completely different principles. If the heater is convection, then there is a heating element inside it. Through holes in the bottom of the device, cold air enters this element and heats up. Having become lighter, it rises through the holes in the upper part of the structure, and a new portion of cold air enters in its place.

If the heater works on the principle of infrared radiation, then the heating element creates infrared rays, which are invisible, but carry thermal energy. Surfaces, objects and people are able to absorb these rays directly, that is, the objects are heated, not the air around them. However, some of the heat from objects and surfaces still enters the air due to the heat transfer of these objects themselves. 

Finally, exist Also oil heaters - their difference is that the heating element transfers heat not into the air, but into a special mineral oil, which has a high heat capacity. Therefore, the oil heater continues to heat the room for a long time after it is disconnected from the power supply.

As can be seen from the operating principles of various electric heaters, none of them absorb oxygen. However, there are methods of heating rooms that require oxygen, for example, a lighted fire or a burning fireplace. Although they do not burn oxygen, they require it to support combustion. However, you need to understand that oxygen consumption in the room occurs near the combustion source, where heated oxygen-depleted air quickly rises and leaves the room, thereby providing an influx of new fresh air from outside, unless, of course, we are talking about completely sealed spaces. 

The main danger of heating rooms using open combustion is not the absorption of all the oxygen, but the allocation carbon monoxide. They can be poisoned unnoticed, even to the point of death. However, carbon monoxide is not emitted by convection, infrared, or oil heaters.

The widespread gas space heaters stand apart. The principle of their operation is based on the so-called flameless combustion of a mixture of liquefied gas (propane-butane) and air, which evenly heats the heating element to a high temperature. In this case, it is necessary that the room is well ventilated, because oxygen for flameless combustion is taken directly from the room in which the gas heater is installed. Accordingly, the oxygen content in a closed room without good ventilation will gradually decrease.

In this case, a subjective feeling of lack of air or difficulty breathing may occur for other reasons. Firstly, if a poorly cleaned room is heated or the heater itself is not cleaned in time dust, there is a possibility that this dust will burn. This is only possible in devices where there is an open heating element or fuel combustion occurs. 

From this point of view, infrared and oil heaters are completely safe, although even if they are covered with dust, it is better to wipe it off before use, otherwise dust will circulate along with the movement of air around the room. Secondly, difficulty breathing may be associated with excessive dry air, which a heater can aggravate. Therefore, in the room where the heater is used, you need to regularly clean it and monitor the air humidity.

Thus, infrared and oil heaters do not consume oxygen from the air, unlike gas heaters, which require good ventilation of the room. Stoves and fireplaces also consume oxygen, but in these cases natural ventilation is provided by a chimney installed directly above the open fire.

Cover image: Hans. Heating and air

Update October 17, 2025: The text has been updated to include information about the oxygen consumption of gas heaters and an explanation of why rooms in which the heater is used may feel starved of air. The previous version can be found at link.

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