Is Chlorine Gas Flammable? (A Comprehensive Overview)

Is Chlorine Gas Flammable?

Chlorine gas(Cl2 or Cl2(g)), itself is not flammable or combustible, but it can cause fires or explosions by reacting with other substances such as hydrogen gas (H2). Also, chlorine can form flammable compounds when mixed with other substances such as ammonia (NH3).

Chlorine is a strong oxidizer and as such it can promote violent chemical reactions. Some such chemical reactions can produce enough heat to cause a fire or an explosion.

At regular conditions chlorine is a yellow-green gas with a pungent smell similar to bleach (NaClO). If inhaled, chlorine gas can cause severe health issues and even be lethal.

Nonetheless, chlorine is widely used in the production (as a raw material or as an additive in the process of production) of chemicals present in everyday life such as bleach, pesticides, rubber and solvents.

What Is The Difference Between The Chlorine Element And Chlorine Gas?

The chlorine element (Cl) has highly different properties than chlorine gas and it is present in many natural and synthetic compounds. The chlorine element usually performs either on covalent bond with another element or an ionic bond when it is in the form of an anion.

The chloride anion (Cl) is present in human physiology, in salt (NaCl), in food preservatives and many other materials.

Chlorine gas is a substance made of molecules of two chlorine atoms having on covalent bond with each other (Cl-Cl or Cl2). At regular pressure chlorine gas turns into liquid chlorine at temperature below -34 ºC (-29 ºF) and into a solid below -101 ºC (-150 ºF).

Chlorine gas has a density 2.4 times that of air, for that reason  it tends to stay near the ground when it is released or leaked in the ambient.

Some chlorine gas properties at 20 ºC (68 ºF) and/or 1 atm of pressure.

AppearanceYellow gas
Melting point-101 ºC (-150 ºF)
Boiling point-34 ºC (-29 ºF)
Vapor pressure6.4 hPa
Relative density (air = 1)2.44
Water solubility7.4 g/l

Fire Hazards Of Chlorine Gas

Chlorine is a strong oxidizer and as such it can cause fires when in contact with both a flammable material and an ignition source.

Chlorine can also intensify an already occurring fire.

Chlorine does not catch on fire by itself or in the presence of only air or only oxygen.

Chlorine Can Cause A Fire If In Contact With Some Metals

When in contact with some chemicals that are pron to be oxidized there is risk for fire start or explosions.Metals that can react violently with chlorine  include:

  • Copper (Cu0).
  • Aluminum (Al0).
  • Tin (Pb0).
  • Iron (Fe0).
  • Metals from the group 1 and 2 on the periodic table.

For instance, when a hot metal such as copper goes in contact with chlorine gas the metal is rapidly oxidized to copperII chloride (CuCl2) producing a large amount of heat.

The heat produced in the oxidation of copper by chlorine gas can lead to an explosion or serious incidents.

Reaction Between Chlorine Gas and Hydrogen Gas can Cause Serious Incidents

The oxidation of hydrogen gas (H2) by chlorine gas produces hydrochloric acid (HCl) and is highly exothermic (that is releases a high amount of heat). The heat generated can promote the ignition of the mixture or promote the oxidation of hydrogen by oxygen (O2).

Furthermore the product of the reaction, hydrochloric acid, can itself be very dangerous as it is a highly corrosive, nocive and unstable gas.

Mixing Chlorine Gas And Ammonia Is extremely Dangerous

The highly toxic gas monochloramine (ClNH2 or just chloramine) is formed from chlorine gas and ammonia (NH3). Monochloramine can be formed in aqueous solution as well and is used in water treatment at maximum allowed concentration of 4 parts per million (ppm).

The median lethal oral dose of pure monochloramine in rats is 935 mg/kg and short exposure to it can cause severe health problems.

Monochloramine is combustible and can ignite in the presence of an ignition source if it is heated for some amount of time.

Unsaturated Hydrocarbons Can Combust In Contact With Chlorine Gas

Unsaturated hydrocarbons such as ethene (C2H4) and acetylene (C2H2, also known as thyne) when combined with chlorine gas is readly and strongly oxidized. Since molecules such as acetylene and ethene are highly flammable the heat can easily generate a fire or explosion.

Reaction between acetylene and chlorine gas ultimately forms hydrochloric acid and carbon in reaction that may proceed by a radical mechanism. One of the factors that led to the mixture igniting is the high amount of heat that the reaction produces.

Turpentine oil (a mixture of mostly unsaturated hydrocarbons) also ignites in contact with chlorine gas as well as with fluorine gas (F2).

How To Put Out Chlorine Fire?

The suitable extinguishing media for chlorine fire is: water spray, alcohol-resistant foam, dry chemical, or carbon dioxide. To cool unopened containers/tanks with chlorine use water spray.

How Toxic Is Chlorine Gas?

Exposure to chlorine chlorine can cause:

  • Mild nose irritation
  • Eye irritation
  • Throat irritation.
  • Immediate chest pain, vomiting, changes in breathing rate, and cough
  • lung injury and pulmonary edema
  • Death after 30 minute to 430 ppm
  • Death after a few minute exposure to 1,000 ppm 

Subjects who are regular smokers, or that suffer from respiratory conditions, are more likely to present more severe symptoms than healthy individuals or nonsmokers.

Where Is Chlorine Gas Found?

Chlorine gas is widely used by the chemical industry and in water treatment.

Since chlorine gas is highly unstable it is hardly found in the environment.

As chlorine gas is more dense than air, if it is released in the environment it stays near the ground and can travel some distance until it is completely decomposed.

What Is Chlorine Gas Used For?

Chlorine gas is widely used in water treatment.

Water and chlorine gas undergo a chemical reaction when they are mixed together in which hypochlorous acid (HClO) and hydrochloric acid (HCl) are primarily formed (in this reaction chlorine is going through a disproportionation reaction).

Hypochlorous acid is very effective for eliminating microorganisms. This acid acts both by decreasing the pH (increasing the acidity) and by oxidizing organic matter.

While in water hypochlorous acid is partially converted to chlorateI (CIO) and hydronium (H3O+), chlorateI is also very effective in eliminating microorganisms.

Conclusion

Chlorine gas has high exposure and fire hazards.

Chlorine gas is widely used as a raw material of important chemicals.

Chlorine gas should only be handled in well prepared facilities using the proper safety measures.

Frequently Asked Questions (FAQ): Is Chlorine Gas Flammable?

Does chlorine burn in air?

Chlorine gas does not burn in air alone. Chlorine gas can cause or support combustion of a series of flammable substances under certain conditions. Flammable substances such as hydrogen gas or acetylene can catch on when mixed with chlorine gas, even in absence of oxygen.

Is chlorine water flammable?

Chlorine gas is not flammable but it can cause some flammable materials to ignite. The chlorine in water is not chlorine gas but hypochlorite acid and chlorateI anion (those substances are formed when chlorine gas is dissolved in water) and these are not flammable either. 

Is bleach flammable?

No, bleach is not flammable. But as a strong oxidizer it can cause other materials to catch on fire if under heating for some period of time. Bleach can also produce toxic gasses when mixed with chemicals.

Does chlorine gas go away on its own?

Chlorine gas has a half-life in the environment of around 1.3 to 5 hours. Chlorine is denser than air and so it does not easily dissipitas but since chlorine is quite reactive with water and with sunlight it usually decomposes in a few hours.

How do you get rid of chlorine gas?

Since there are no antidotes for chlorine exposure. The recommended treatment is removing the chlorine from the body as quickly as possible and providing medical attention such as inhaled breathing treatments for wheezing.

How do you handle chlorine gas?

The recommended wear is: a face shield, safety goggles, chemical protective clothing.

Is bleach the same as chlorine?

No, bleach usually refers to a powder or aqueous solution containing the chemical sodium hypochlorite (NaClO), which does contain the element chlorine but is not the same as chlorine. Chlorine can refer to either the element chlorine (Cl) or the chlorine gas (Cl2). The chlorine element is present in many different materials in anionic, and even in cationic form in many different types of materials, dissolved in the ocean and in most living organisms. Chlorine gas is a unstable and hazardous chemical with many applications in industry.

References

Chlorine safety data sheet: 

https://www.sigmaaldrich.com/US/en/sds/aldrich/295132 (Accessed August 09th, 2022)

Some general information on chlorine gas:

https://emergency.cdc.gov/agent/chlorine/index.asp (Accessed August 09th, 2022)

Toxicological information on chlorine:

https://wwwn.cdc.gov/TSP/substances/ToxSubstance.aspx?toxid=36 (Accessed August 09th, 2022)

https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=1079&tid=36 (Accessed August 09th, 2022)

https://www.atsdr.cdc.gov/ToxProfiles/tp172-c1.pdf (Accessed August 09th, 2022)

Some hazards of chlorine:

https://www.chlorineinstitute.org/stewardship/chlorine/other-hazards/  (Accessed August 09th, 2022)

Information on firefighting measures on chlorine fire:

https://webwiser.nlm.nih.gov/substance?substanceId=338&catId=60 (Accessed August 09th, 2022)

Information on the reaction between chlorine and acetylene:

https://edu.rsc.org/experiments/the-reaction-of-ethyne-with-chlorine/1780.article (Accessed August 10th, 2022)

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