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?
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.
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.
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).
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.
