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There is a popular belief in Russia that electric heaters with an open nichrome heating element (red hot) "burn up oxygen" and "dry the air", unlike oil-filled ones.

Is it true that a Joule heater with an open heating element would reduce absolute humidity (i. e. total amount of water) or amount of oxygen in a room?

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To "burn oxygen" you need a chemical reaction ... –  belisarius Oct 18 '11 at 1:31
    
@belisarius: like with dust? –  Quassnoi Oct 18 '11 at 7:09
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“burn oxygen” is a nonsense claim. Burning, by definition, is oxidisation. –  Konrad Rudolph Oct 19 '11 at 9:31
    
I have been trying very hard to dig into this issue. I have observed a very definite reaction to space heaters, but I'm not sure of the reason. Unfortunately, I have very little scientific background, not having paid attention enough to science classes when I was young. However, it looks to me as though the chromium oxide layer that forms does not perfectly prevent all future oxidation. I found the following from a website belonging to a company that claims to design and manufacture heating elements: "The resistance of the elements will increase with age, due to the reduction in cross section –  user11276 Jan 27 '13 at 1:17
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I suspect "burn oxygen" is a just a mistranslation which should be "burn up oxygen". –  Oddthinking Jan 30 '13 at 22:56
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up vote 14 down vote accepted

Heating will have no effect on the oxygen level in the air unless something burns, which will use up oxygen. This is basic chemistry. An electrical heater heats because electrical current passes through it, not because anything burns, so oxygen levels cannot be directly affected. Most burning reactions in the normal atmosphere involve things burning in oxygen: it isn't obvious that the phrase "burn oxygen" means anything at all. This is all basic school level chemistry (so deserves a wikipedia reference). Here is the Wikipedia definition of combustion:

Combustion (English pronunciation: /kəmˈbʌs.tʃən /) or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species.

The other part of the claim that electric heaters dry the air is partially true depending on the definition of humidity. The humidity you experience is the relative humidity defined by Wikipedia as:

Relative humidity is defined as the ratio of the partial pressure of water vapor (in a gaseous mixture of air and water vapor) to the saturated vapor pressure of water at a given temperature. In other words, relative humidity is the amount of water vapor in the air at a specific temperature compared to the maximum water vapor that the air is able to hold without it condensing, at that given temperature.

If air is warmed in a closed room the amount of water won't change but the relative humidity will since warm air holds more water than cold air. So the air will feel dryer. Unfortunately the question specifies absolute humidity (or the total amount of water) and just heating does nothing to the amount so the answer is no, heaters don't dry the air.

But i'm prepared to be generous and allow that electrical heaters will make air feel dryer. This is in contrast to oil or gas heaters which deplete oxygen and give off water and carbon dioxide (and some monoxide if not well maintained). In a sealed room you will eventually suffocate from lack of oxygen and presence of carbon dioxide. In a ventilated room an oil or gas heater will leave higher humidity than an electrical heater because they do release water but the electrical heater does not.

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You do not have to burn something to consume oxygen - oxidation –  Chad Oct 19 '11 at 14:50
    
@Chad strictly true but irrelevant. Rusting consumes oxygen, for example, but this has nothing to do with what the question asked unless some other mechanism for using oxygen is proposed which it wasn't. –  matt_black Oct 19 '11 at 14:57
    
"This is in contrast to oil or gas heaters which deplete oxygen and give off water and carbon dioxide" Won't those be given off in the chimney? You also said: "If air is warmed in a closed room the amount of water won't change but the relative humidity will since warm air holds more water than cold air." Well... No house is perfectly closed... –  Uwat Mar 1 '12 at 21:04
    
@Uwat - Actually, no, not all heaters send their exhaust through a chimney. Some heaters dump their exhaust into the indoor air. Is this good? No, I'd generally not suggest those heaters be used in a closed room, but they are still used. –  user3344 Nov 17 '12 at 14:11
    
@Uwat - A closed house is irrelevant. Warming the air will still reduce the relative humidity. Warmer air holds more water, so the relative humidity is reduced. In fact, if outside air is taken in and then warmed, it will tend to dry things out even more, since it was presumably colder outside the house. –  user3344 Nov 17 '12 at 14:16
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TL;DR; - Oxygen is consumed during the initial burn that creates the Oxide "Shell". Once the coating is there the chromium is protected from further oxidation so the answer becomes no. Though the amount of oxygen that it consumes will be negligible under normal circumstances.

Most heating elements use Nichrome 80/20 (80% nickel, 20% chromium) wire, ribbon, or strip. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time. Material beneath the wire will not oxidize, preventing the wire from breaking or burning out.

Source

So the first time when it creates the oxide coating yes it ill consume oxygen to create the Chromium Oxide. After the initial coating the metal resists oxidation so it should consume little if any oxygen unless the oxide coating is removed.

Oxidation resistance can be attributed to the formation of a highly adherent protective scale. The adherence and coherence of the scale can be improved by the addition of small amounts of other reactive elements such as zirconium, silicon, cerium, calcium or similar. The scale thus formed is a mixture of nickel and chrome oxides (NiO and Cr2O3).

Source

The source above has confirms the Wikipedia site description of the Oxide process

As for the humidity, the chart here shows how relative humidity changes by temperature. The fixed measurement is "absolute humidity" and is measured in grams per cubic meter. As temperature increases the absolute humidity will stay the same but the relative humidity, how it feels, goes down. So the effect is it feels like the air is dryer but there is the same amount of moisture in the air.

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So was that a yes or a no? –  matt_black Oct 18 '11 at 19:48
    
I will +1 if you put that statement/ a TL:DR up top ;) –  Stefan Jan 27 '13 at 16:36
    
Thanks +1 ----- –  Stefan Jan 30 '13 at 18:31
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Dust is incinerated in close proximity of a very hot surface. Burning consumes oxygen. The dustier is the air the more oxygen is lost.

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This might be a good answer if you quantified the effect and provided some evidence about what dust contains and how much there is in a typical room. –  matt_black Nov 17 '12 at 17:15
    
Hi trupudor! Welcome to the site. This site is a little different. To improve your post, please cite your sources! You can read more about the page in this post. –  gerrit Nov 17 '12 at 21:37
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