Is an Oxygen Tank Flammable? (A Comprehensive Overview)

Is an Oxygen Tank Flammable?

An oxygen tank is not flammable, nor is oxygen. However tanks containing oxygen in gas or liquid form pose risks for explosions, as is the case for most pressurized compartments. 

Additionally, if accompanied by heat and a material that can catch on fire (a combustible material), they have a secondary hazard of fire, or fire followed by explosion.

Oxygen Tank Related Fire Hazards

Materials that are not flammable under ordinary circumstances can catch on fire more easily if a large amount of oxygen is present.

Unlike air, compressed air, nitrogen gas (N2), argon gas (Ar) and helium gas (He), oxygen is considerably unstable.

Regular air has around 21% volume of oxygen. If the concentration of oxygen in air is increased to only 24%, dangerous situations may take place:

Fires are more likely to start, said fires burn hotter and with higher increments to pressure than everyday fires. Fires caused in this manner are also harder to pull out.

High concentrations of pure oxygen, as is the case in oxygen cylinders, can react violently with oils, grease, textiles, rubber and metals.

An oxygen tank can can cause a fire or an explosion if:

  • Container is heated.
  • Container is mechanically damaged.
  • Valves being damaged.
  • Oxygen enrichment from leaking equipment.
  • Contact with materials not compatible with oxygen.
  • Using the oxygen with equipment not well suited for oxygen procedures.
  • Too much oxygen is released at once.
  • If the oxygen tank or oxygen gas is in contact with a fire.

Oxygen Enrichment

When the oxygen level (oxygen concentration in the ambient air) is higher than 21% (21% is the normal oxygen concentration in air) it can be said that the ambient has an oxygen enrichment.

The main hazard associated with an oxygen enriched atmosphere is that people’s clothes or hair can easily catch on fire under these circumstances. 

A fairly possible scenario is if smoking near an oxygen tank is being used for therapeutic purposes. This can cause clothing, bedding and or hair to catch on fire causing possibly fatal injuries.

Common causes for oxygen enrichment include:

  • Damaged or poorly maintained connections,hoses, pipes and valves.
  • Left open valves (deliberately or accidentally).
  • Excessive use of oxygen in flame cutting welding or related procedures.
  • Lack of ventilation in spaces where oxygen is being used.

Recommended Measures to Prevent Oxygen Enrichment

Following are some methods to reduce the likelihood of oxygen enrichment to occur:

  • Monitor the conditions of the oxygen tank and associated equipment.
  • Make sure the room has good air ventilation.

Oxygen should never be employed to:

  • To cool or refresh the ambient air (especially in confined rooms).
  • To dust benches, cloth or machinery.

Recommendations to Follow In Case of Oxygen Enrichment

In case of confirmed or suspected oxygen enrichment in a given space, the following are some important recommendations:

  • Cut off the oxygen source (usually closing the oxygen tank valve).
  • Ensure there are no flames or parks in the vicinity.
  • If there is no ventilation in the room, proceed to open windows and doors if possible.
  • Verify if there’s any oxygen leakages. If that’s the case, repair it.

Oxygen can, in some cases, accumulate in clothing, sheets and towels in case of contamination or suspicion of, remove the clothing and provide ventilation.

In case of a fire starting, personal evacuation may be the safest procedure.

Fire Hazards in Confined Spaces

A confined space can be considered any room which has no openings, poorly ventilated rooms also pose dangers. When a given pressurized gas is released in a confined space, the concentration of said gas will start to increase. 

If said gas is oxygen the risk for a fire to start is very high since the ability of any material to catch on fire increases proportionally to the oxygen concentration.

Gas cylinders or tanks must not be taken inside confined spaces. Instead, hoses to feed the gas in should be used.

It is recommended to use oxygen monitoring apparatus when there is possibility for oxygen enrichment.

Recommendations for Commonly Used Equipment in Oxygen Gas Systems

The equipment and apparatus designed for oxygen gas delivery systems are made of oxygen compatible materials. Said equipment and apparatus have been properly evaluated and tested and are considered safe for this purpose.

Accidents are prone to happen if equipment that is similar but not proven safe for oxygen gas systems.

The design, construction and installation of oxygen gas systems must always be performed by competent personnel with the proper knowledge.

Any oxygen apparatus and equipment must be properly labeled with the gas name

and with the safe working pressure.

Following are some general equipments and their respective recommendations for usage in oxygen systems:

O-Rings and Gaskets

A huge number of the different types of rubber are made of materials incompatible with oxygen.

A proper information source (such as the oxygen tank provider) should be consulted prior to using any elastomer or rubber.

Metal Components

Many metals and alloys are not suitable for use with oxygen. Most metal made materials will readily be oxidized by oxygen, when oxygen is present at concentrations higher than 21%. 

Such strong oxidations can produce enough heat to cause fires or even explosions if at pressurized or confined spaces.

Pressure Regulators

The pressure rating of the pressure regulator must be at least equal to the tank or cylinder supply pressure output.

For gas welding the pressure regulators should be in accord with BS EN ISO 25033. For oxygen cylinders used in medical installations they should be in accord to BS EN ISO 10524.4

Oxygen hoses

Oxygen hoses to be used must be used according to BS EN ISO 38215 or BS EN ISO 5359.6.

Lubricants

Lubricants which contain any amount of organic substances pose a high risk of igniting under high concentrations of oxygen. Lubrificants fabricated specifically for oxygen usage procedures should be used.

Tape

Some common tapes may be unstable and can catch on fire if in atmospheres rich in oxygen. The only tape that can be used are the ones specified by the specific oxygen tank supplier.

The Flammability of a Given Material is Proportional to the Concentration of Oxygen

Air has a pretty constant concentration of oxygen, if no oxygen was present in the air most materials would not catch on fire at all.

Fires are essentially  the result of a combustion reaction of some sort. This type of chemical reaction requires an oxidizing agent, the most prevalent oxidizing agent on Earth is oxygen.

Therefore the flammability of materials is usually measured related to the concentration of oxygen in the air.

If the concentration would be different, the flammability range of a given material would also be different. Generally, if the concentration of oxygen in the air increases, materials in the same environment will be more likely to catch on fire in comparison to the regular air.

In other words, an increase in the oxygen concentration will induce an increase in the likelihood of things catching on fire.

This can be better explained using a flammability diagram.

Oxygen Tank Uses

Oxygen tank is used in flame cutting, steelworks and welding. In treatments for people with breathing related health issues or in hyperbaric chambers as medical treatment.

In chemical procedures both in industry and research. And also in food preservation and packaging.

Oxygen General Characteristics and Properties

Bellow some properties of the oxygen gas are presented:

Property denominationProperty value
Appearance, odor and taste in gaseous stateColorless, odorless and tasteless
Density at 0 ºC and 1 atm1429 kg/m3
Boiling point at 1 atm−183 °C
Melting point at 1 atm-218 ºC
Molecular formulaO2
Molecular weight32 g/mol
Typical oxygen tank inner pressure (full tank)2,000 to 3,000 psi (136 to 204 atm)

Conclusion

The question: is an oxygen tank flammable answered. Some important recommendations and fundamentals regarding oxygen tanks were discussed.

Frequently Asked Questions (FAQ): Is an Oxygen Tank Flammable?

Can oxygen ignite flammable vapors?

Flammable vapors can be ignited as long as there is an ignition source even without any source of oxygen besides the air. If an oxygen source, such as an oxygen tank is providing oxygen into the same space where there’s flammable vapors the risks of fires and explosions is significantly higher. Not only will the flammable vapors be more easily ignited in comparison to regular air, but the ignition will be more violent and explosive. It is of note that in cases of absurdly high concentrations of the flammable vapor or the oxygen, ignition may not be possible, but such situations are extremely unlikely.

Will fire continue its flame in the absence of oxygen?

An existing fire can only continue if there is an oxidizing agent that is capable of oxidizing the fuel (the combustible) at a specific rate. By far, the most common oxidizing agent in a fire is oxygen (O2). So, in the vast majority of fires, absence of oxygen will lead to absence of fire. But, it is completely possible to initiate, increase or maintain a fire without oxygen, as long as there is a proper oxidizing agent present in the mixture.

Can an oxygen tank catch fire?

No, but if an oxygen tank is in contact with a fire, the tan can be damaged enough to release the pressurized oxygen. If that happens, the fire will surely increase drastically and a strong explosion may take place. High pressure oxygen can also cause otherwise non-flammable materials to turn flammable (e.g. clothing)

Are oxygen tanks explosive?

As long as the proper equipment is used by professionals in the subject, oxygen tanks are not explosive. Using oxygen tanks without the proper safety recommendations can lead to serious accidents, including explosions.

At what percent does oxygen become flammable?

Oxygen itself is not flammable. Flammable materials are so considering the normal oxygen concentration in air (21% in volume). If less oxygen than 21% is present in the atmosphere the flammability of materials decreases (that is, they are harder to ignite). On the contrary, if the concentration of oxygen exceeds 21%, flammable materials will become more flammable, and some non-flammable materials will become flammable.

How does oxygen cause fire?

Fire is the result of a series of processes, the initial process is a combustion reaction. A combustion reaction is an oxidation reaction in which a substance is oxidized by an oxidizing agent. The fuel in a fire is the substance that is oxidized and the substance that causes the oxidation is the oxidizing agent (which is commonly the oxygen, O2, in the air). Not every combustion reaction leads to fire, a fire also requires that the combustion reaction releases a sufficient amount of energy that is capable of ionizing the gas molecules being produced during the combustion. The flame we see is a result of the ionization of molecules in the gaseous state.

References

https://www.cdc.gov/niosh/mining/userfiles/works/pdfs/tloca.pdfhttps://www.cdc.gov/niosh/mining/userfiles/works/pdfs/tloca.pdf

https://www.nfpa.org/~/media/4B6B534171E04E369864672EBB319C4F.pdf
https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=55
https://www.hse.gov.uk/pubns/indg459.pdf

www.hse.gov.uk/pubns/INDG258.htm

www.hse.gov.uk/pubns/books/HSG139.htm 

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