Why does oxygen support combustion

Burns (chemistry)PharmaWikiWhen it burns, a fuel such as wood, gasoline or ethanol reacts with oxygen or another oxidizing agent. It is an exothermic chemical reaction in which heat, light and fire can be released. Burns can also be slow and go unnoticed, such as iron rusting. Many combustion products are harmful to human health and can cause respiratory diseases and cancer.

synonymous: Combustion

Note on this article

This article applies to chemical burns. See also → Burns (medicine).


In chemistry, combustion usually means oxidation, during which heat, light, fire and energy are released.

For example, the alkane octane is an important component of gasoline:

In this reaction, the alkane is oxidized by the oxygen in the air. This creates the gas carbon dioxide and water vapor. The released energy drives cars with an internal combustion engine, for example.

It is a redox reaction in which octane acts as a reducing agent and oxygen as an oxidizing agent.

We are familiar with various fuels from everyday life, for example wood and other plant materials, coal, diesel, methane gas (natural gas), ethanol or beeswax. All of these substances have a very high carbon content. Substances are therefore flammable in all aggregate states - liquids, solids and gases.

Activation energy is required to start the reaction. For example, energy must first be supplied to the wood with a kindling aid and an already burning match.

Combustion of compounds with other elements

The oxidation of other chemical elements and compounds is also referred to as combustion. For example, sulfur burns with a blue flame to form toxic sulfur dioxide (SO2):

Even metals can "burn", for example elemental magnesium:

Burning magnesium cannot be extinguished with water because magnesium reacts with water to form hydrogen, which is also combustible!

When hydrogen is burned, water is produced. It is the so-called oxyhydrogen reaction:

The oxidizing agent does not necessarily have to be oxygen either - there are others such as chlorine gas or fluorine.

Oxidations that proceed slowly or unnoticed, such as the rusting of iron (formation of iron oxides) or the generation of energy in the mitochondria are referred to as "silent burns".

Consequences for health and the environment

In the case of burns, the smoke often releases gases and compounds that are harmful to the human body and especially the respiratory tract. One important reason for this is that combustion is often incomplete, i.e. carbon monoxide is formed instead of carbon dioxide, for example. Other compounds are, for example, nitrogen oxides, polycyclic aromatic hydrocarbons and aldehydes. The formation of fine dust poses an additional problem.

Burns can also have a negative impact on the environment, for example through the excessive formation of greenhouse gases such as carbon dioxide.

see also


  • Adler T. Better burning, better breathing: improving health with cleaner cook stoves. Environ Health Perspect. 2010, 118 (3), A 124-9 Pubmed
  • Specialist literature
  • Chemistry textbooks

Conflicts of Interest: None / Independent. The author has no relationships with the manufacturers and is not involved in the sale of the products mentioned.

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This article was last changed on 11/18/2020.
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