Is Oxygen flammable? (A comprehensive overview)

This article will give you the answer to the question “Is Oxygen flammable?” and it will explain to you what exactly oxygen is. The article will also help you to understand the importance of oxygen, its flammability, properties and its uses.

Is Oxygen flammable?

No, oxygen is not flammable. Oxygen is a gas which has a high amount of energy. Although oxygen is not flammable, for any substance to burn, oxygen is a very necessary element. 

Oxygen is a non-metal and chemical element which is highly reactive. It can exist as a liquid in very low temperatures.

The symbol, atomic number and atomic mass of oxygen are given below:

  • Symbol: O
  • Atomic number: 8
  • Atomic mass: 16.00 g/mol

Discovery of Oxygen 

Joseph Priestly discovered oxygen in 1774, while he was figuring out how things burned. By heating a burning glass and mercury oxide, he produced oxygen. During this, he found that oxygen is not dissolvable in water and it aids the burning process.

Oxygen (as a chemical element)

Oxygen is a chemical element that is non-flammable and highly reactive. It is one of the most abundant elements in the atmosphere and every living organism relies on oxygen for its survival. Living organisms use oxygen for their respiration as this helps in producing energy in them for life to sustain.

Oxygen forms oxides with most of the other elements and hence it is known as an oxidizing agent. This happens as a result of gaining electrons from the other element and thereby reducing itself.

Physical Properties of Oxygen 

The physical properties of hydrogen are given below:

  • The boiling point of oxygen is −182.9 °C
  • The melting point of oxygen is  ​−218.3 °C
  • The density of oxygen is 1.429 g/L at standard temperature and pressure (STP)
  • The triple point of oxygen is 54.36 K, ​146.3 Pa
  • The critical point of oxygen is 154.59 K, 5.043 MPa
  • The heat of vaporization of oxygen is 6.62 kJ/mol 
  • The heat of fusion of oxygen is 0.44 kJ/mol
  • The molar heat capacity of oxygen is 14.7 J/(mol·K)

Allotropes of Oxygen

There are different forms by which an element exists physically. These different forms are known as allotropes. Similarly, oxygen exists in four known physical forms, they are:

  • Dioxygen or O2
  • Ozone or O3
  • Tetraoxygen or O4
  • Metallic oxygen 


This is the most common allotrope of oxygen. It is colorless and has the symbol O2. The atmosphere of the earth consists of almost 21% of dioxygen.


This is a less common allotrope of oxygen. It is blue in color and has the symbol O3.  It has a very different sharp odor and it is a harmful gas. 

It is found as a layer above the atmosphere that is responsible for protecting the earth from the harmful UV rays of the sun. Ozone can be produced by our human immune system and it is produced by electrostatic discharge as well.


This is a relatively new allotrope of oxygen. It is red in color and has the symbol O4. It is produced when dioxygen is subjected to high pressure. This allotrope of oxygen has potential use in fuels. It also has a much stronger oxidizing capacity.

Metallic Oxygen: 

Under a pressure of about 96 GPa, Tetraoxygen becomes metallic in nature. This situation is true in the case of gasses like hydrogen as well.

Flammability and combustion of Oxygen 

Oxygen is not a flammable gas, but it is an oxidizer. This means that it will react quickly without any external input of energy. It is due to the ability of oxygen to readily combine the other chemical elements.

Oxygen requires fire and it is hazardous to keep any flammable substance in an oxygen-rich environment. This is because it will aid fire to burn rapidly. Therefore, we can say that oxygen is a non-combustible gas. It only aids the combustion process.

Uses of Oxygen

Oxygen is one of the most important gases on earth and about 21 percent of the atmosphere is composed of it. Oxygen plays a crucial role in the system of plants, animals and humans. All the cells in these systems require a continuous supply of oxygen in order to function well. Apart from this, the applications of oxygen are widespread.

Some of the uses of oxygen are:

  • Industrial uses
  • Physiological uses
  • Aerospace uses

Industrial uses:

A variety of industrial processes use oxygen, including steelmaking, metal refining and fabrication, petroleum refining, pharmaceuticals, production of ceramics and glass, and pulp and paper making.

In steel making, a blast furnace uses oxygen to convert carbon to carbon dioxide gas at high temperatures. As a result, iron oxides are reduced into pure iron compounds when carbon dioxide is produced.

In metal refining, there are applications for oxygen, such as welding torches, that involve metal and require high temperatures.

In the petroleum industry, the coal gasification process uses a large amount of oxygen. In this process, oxygen is used to create synthesis gas that can be used as a chemical feedstock to produce more easily transportable fuels. Also, in catalytic cracking regenerators are enriched with oxygen, which increases their capacity. Regenerating catalysts is another use of oxygen in this industry.

In pharmaceuticals, especially for processes involving oxidation, oxygen is used as an important raw ingredient. Oxygen is a key ingredient in the manufacture of propylene and ethylene oxides. Synthesis gas is also produced by the oxidation of hydrocarbons, nitric acid, etc.

In the ceramics and glass industry, oxygen is used for the complete combustion of the material as it aids the combustion process and makes it efficient. Use of oxygen results in lower consumption of energy, lower emissions and thereby saving fuel costs. 

In the pulp and paper industry, oxygen finds its application in the bleaching processes. Oxygen is used to remove the lignin in the pulp, and this is employed by using oxygen. When oxygen is employed in the combustion process, it increases the capacity of production of the reburning the kiln of lime and the capacity of production of soda recovery in a pulp mill. Oxygen is mainly employed, as the use of other elements may lead to air and water pollution.

Physiological uses:

Most of the living organisms use oxygen for respiration, such respiration involving oxygen is called aerobic respiration. This kind of respiration utilizes energy from the food that these organisms consume and convert it into energy. Humans with health disorders may have a lack of oxygen in their system which can lead to respiratory issues, hence oxygen is used in health care units for inhalation therapies, surgeries, etc.

At high elevations, mountaineers use compressed oxygen tanks to compensate for the decreased oxygen pressure.

For sterilization purposes, by exposing certain anaerobic bacteria to surplus oxygen, certain anaerobic bacteria can be killed.

Aerospace uses: 

Since oxygen is a strong oxidizing agent, it is used in rockets and missiles. During takeoff, liquid hydrogen reacts with oxygen to produce a tremendous thrust which is essential for such machines. 

The space suits used by astronauts require a pure form of oxygen (approximately 92-96%) for their respiration as there is no natural oxygen in outer space. 

In the generators of aeroplanes and helicopters, it is necessary to use oxygen gas to generate energy as they do not have their own electrical supply.

Hazards of Oxygen

We know that oxygen has numerous uses and it is very important for plants, animals and humans to survive. But, it is stunning that oxygen can be harmful in some situations, especially while using oxygen cylinders. The nature and reactivity of oxygen are quite different when it is in compressed form in cylinders. Pure oxygen, at high pressure, will react violently with common materials such as oil, rubber and metals. 

When the oxygen in the air increases, it can become dangerous when it reaches above 24%. This condition is called enrichment of oxygen. In such cases, it will be extremely difficult to put out a fire. 

Some of the causes of enrichment of oxygen are:

  • Leakages of oxygen are caused due to worn out valves and pipes.
  • Accidental leakage of oxygen from improper handling of hoses and pipes.
  • Improper closing of valves
  • Usage of surplus oxygen for welding and fitting purposes.
  • Bad ventilation area where oxygen is used.


This article addresses the question “Is Oxygen flammable?” 

The article has given a comprehensive overview of oxygen and its flammability. The article has also given information about the physical properties, discovery, uses and hazards of oxygen. 

Please do not hesitate to comment on the above content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): Is Oxygen flammable?

Why is oxygen not flammable?

It is not possible for oxygen to burn which is why it is not flammable. But, we can say that oxygen supports the burning process. This means that in the presence of oxygen, things tend to burn better.

What does oxygen do to the fire?

For a fire to occur, oxygen is necessary. Oxygen is one of the elements without which fire cannot be created. In cases when a fire has to be put off, the oxygen source should be removed, then the fire will be automatically stopped.  For example, when a burning candle is covered or sealed with glass, it immediately stops burning as the oxygen supply is cut off.

At what temperature does oxygen ignite?

Oxygen cannot ignite on its own as it is not a flammable gas. Oxygen can ignite when it is present in combination with other elements. In such cases, the ignition temperature varies according to the element with which oxygen is combined.

Do oxygen cylinders explode?

Since oxygen is not a flammable gas, explosions are very rare. However, it is possible for oxygen cylinders to explode if they come in contact with a flammable material or an element. Explosions are also possible if the storage of oxygen is not done in appropriate cylinders.

Can you have fire without oxygen?

As mentioned earlier, it is not possible to create fire without oxygen. Oxygen is one of the crucial elements without which fire cannot be created.


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