Is Tear Gas Flammable? (A Comprehensive Overview)

Is Tear Gas Flammable?

Tear gas has a low flammability. When subjected to an ignition source such as a naked flame or an electrical spark, most common tear gasses will only catch on fire if they are priorly exposed to high temperatures.

In cases of very high tear gas concentration on air, contact with flames can produce a momentaneous fire that is unlikely to be sustained for more than a few seconds. But a momentaneous fire can ignite flammable materials near it.

That being said, to properly answer whether or not a given tear gas is flammable it is essential to consider the exact composition of the tear gas, as that is the main factor to consider its likelihood of catching on fire.

The composition of tear gasses commonly has two main ingredients: the lachrymatory agent and a medium to cause it to be effectively dispersed in the air.

Furthermore, if tear gasses go in contact with fire, highly hazardous gasses can be released. For instance, burning CS gas releases the deadly gas hydrogen cyanide gas (HCN).

In this article, fire related hazards, health hazards and some physical and chemical properties of the following tear gasses will be presented:

  • CS gas
  • CR gas
  • CN gas
  • Pepper spray

Hazards Related To Tear Gas Usage

Common hazards related to tear gasses are:

  • Symptoms directly caused by contact and inhalation with tear gas.
  • Tear gas cartridges hitting someone.
  • Fire related hazards.

Contact with tar gasses causes:

irritation of mucous membranes in the eyes, nose, mouth and lungs. 

crying, sneezing, coughing, difficulty breathing, pain in the eyes, and temporary blindness. 

The most common tar gas, CS gas, starts to cause symptoms after 20 to 60 seconds of exposure lasting for 30 minutes after contact with the gas is cut.

Tear gas cartridges can cause severe trauma if they directly hit a person. This can cause  bruising, skull fracture, vascular injuries and even death.

Fire hazards associated with tear gasses include potentially very toxic fumes produced by the burning of tear gas and flash fires. Normally, tear gasses are not capable of bursting into flames and starting a fire.

Is CS Gas Flammable?

CS gas is the most common tear gas used in riot control. The lachrymatory agent in CS gas is  2-chlorobenzalmalononitrile (or [(2-Chlorophenyl)methylidene]propanedinitrile, chemical structure represented below).

This substance is combustible, but for it to ignite under an ignition source preheating is necessary. In the table below are shown some physical properties of  2-chlorobenzalmalononitrile (the main ingredient in CS gas).

AppearanceWhyte powder
Melting point at 100 kPa93 °C (199 °F)
Boiling point at 100 kPa310 °C (590 °F)
Vapor pressure at 20 ºC3.4×10−5 mmHg

The means of delivery of this gas varies and so the likelihood of it causing a fire varies as well. Overall, the risks of CS increasing or causing a fire are not very high.

Aerosol Forms Of CS Gas:

  • Melted
  • Dissolved in volatile organic solvent.
  • Micro-pulverized dry powder with silicon (Si)
  • With hot gasses generated from thermal grenades

Burning CS Gas Produces Hydrogen Cyanide Gas

One of the major hazards associated with CS gas and fire is the production of highly dangerous cyanide gas. If the lachrymatory agent in CS gas is subjected to a fire it can release among other gasses, hydrogen cyanide (or cyanide gas).

If inhaled, hydrogen cyanide can be lethal at concentrations of around 100 ppm in air for a few minutes.

Not to mention that hydrogen cyanide is itself highly flammable with a flash point of −17.8 °C (0 °F) and an autoignition temperature of 538 °C (1,000 °F) and with explosive limits between 5 and 40%.

Is CS Gas Toxic?

Aside from the well known effects, CS can cause severe damage to lungs, heart and liver.

In Egypt, during the November 2011 protests CS gas was used and it was reported to be the cause of death of several protesters in Mohamed Mahmoud Street.

The Exposure Limits of CS gas is, on skin, 0.4 mg/m³ (by the NIOSH method). The immediate danger to health or life (IDLH) concentration in air is 2 mg/m³.

Is CR Gas Flammable?

The lachrymatory agent in CR gas is dibenzoxazepine (or dibenz[b,f][1,4]oxazepine,chemical structure shown below), it also has a nickname of ‘firegas’. In its immediate effects CR gas is about twice as potent than CS gas.

In the table below are the main known thermal properties of dibenzoxazepine.

AppearanceWhyte powder.
Melting point  at 100 kPa73 °C (163 °F)
Boiling point  at 100 kPa339 °C (642 °F)
Vapor pressure at 20 °C0.000034 mmHg

Dibenzoxazepine is combustible (that is it can catch on fire) but since it needs considerable preheating for it to ignite it is not considered flammable. Moreover, when used as a tear gas, other substances are mixed with it and it is hard to properly determine its flammability.

Is CN Gas Flammable?

CN is the principal component of the aerosol agent Mace and is widely used in riot control (CN should not be confused with cyanide, CN). The lachrymatory agent in CN gas is Phenacyl chloride (the specific chemical name is 2-Chloro-1-phenylethan-1-one), its chemical structure is represented below. 

This substance is combustible but it requires preheating before it can burst into flames in the presence of an ignition source. Some physical properties of phenacyl chloride are shown below.

AppearanceGrey solid.
Melting point  at 100 kPa54 – 56 °C (129 – 133 °F)
Boiling point  at 100 kPa244 °C (472 °F)
Vapor pressure at 20 °C0.05 mmHg

As with the other tear gasses CN gas likelihood of catching on fire when subjected to an ignition source increases with the temperature and concentration. Under mild conditions CN gas does not immediately catch on fire when an ignition source is applied to it.

Is CN Gas Toxic?

Aside from the well known effects CN can cause syncope, temporary loss of balance and orientation.  In more rare cases, cutaneous irritating outbreaks and allergic contact permanent dermatitis.

When  at high concentrations, CN can lead to corneal epithelial damage and chemosis. CN gas can also cause  pulmonary injury and/or asphyxia, which has accounted for at least five deaths.

Is Pepper Spray Flammable?

Pepper spray composition usually consists of the lachrymatory agent capsaicin (chemical structure shown below), an emulsifier such as  propylene glycol (CH3CH(OH)CH2OH) and water.

Capsaicin can catch on fire only if preheated, while propylene glycol is flammable. However, since both these substances are mixed with water  they are pretty much inert in the presence of ignition sources.

Nonetheless, if pepper spray is ejected into a flame it will likely spread and increase the fire.

Conclusion

Tear gasses are used in diverse situations and in different formulations representing overall mild risks if used responsibly by the competent forces. But, they can be the cause of severe injuries to the population if used irresponsibly.

In this article some key properties and known characteristics of four of the most common tear gasses were briefly discussed.

Frequently Asked Questions

Does tear gas catch fire?

Tar gasses have the ability of catching on fire but for that to happen they need to meet somewhat extreme circumstances of temperature and concentration.

Can you survive in tear gas?

Tear gas immediate effects on most people are relatively mild and last less than an hour after resolving the contact. More extreme situations can take place in enclosed spaces in which cases tear gas can lead to asphyxiation. Furthermore, if a person is subjected to high concentrations or for long periods of time long term symptoms may appear.

Is tear gas poison gas?

Tear gas usually consists of aerosolized solid or liquid substances, meaning they are not gasses per say, but they are considered poison . Symptoms caused by exposure to tear gas range from mild eye irritation to even internal organs damage. The severity of the symptoms are dependent on a number of factors.

How long does tear gas last in a house?

The tear gas cloud dissipates faster if there is efficient ventilation with fresh air. The time also depends on the amount of gas initially propagated.

Is pepper spray the same as tear gas?

Tear gas usually refers to CS gas , CN gas or CR gas and they are used in riot control. Pepper spray is used on much smaller scales, but the effects are similar.

What stops tear gas?

Eye exposures can be treated by rinsing the eyes with water. No antidote exists for poisoning from riot control agents. Burnings in the skin can be treated with medicated bandages.

References

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