Is Gas Flammable? (A Comprehensive Overview)

Is Gas Flammable?

Yes, gasoline is flammable since its vapors will ignite if subjected to a naked flame or an electrical spark under regular conditions (atmospheric air, ordinary temperature and pressure). Gasoline also poses a significant risk for explosions.

Besides, gasoline vapors can travel relatively long distances until a source of ignition. The exact distance is very dependent on the ambient temperature, wind speed and amount of gasoline vapors.

The main physical properties that indicate the flammability of gasoline are 

the flash point, the fire point and the autoignition temperature. Said properties will be discussed below and followed by additional important information about gasoline.

Gasoline Flash Point

The lowest temperature at which gasoline under air has vapors that can be ignited when subjected to a spark or naked flame usually stays in the range between -42 ºC and -23 ºC (-45 ºF and -9 ºF).

The main factor that influences the flash point of gasoline is its composition. Gasoline with higher amounts of aliphatic hydrocarbon tend to have lower flash points. In many cases, ethanol (CH3CH2OH) is added to the gasoline formulation, the flash point of ethanol is higher than gasoline.

In the case of gasoline reaching its exact flash point temperature, it will still be under its fire point. In such a situation if an ignition source is applied to the gasoline vapors, they will burn as a momentary flash, but the combustion will not sustain.

Nonetheless, the flash point of gasoline can vary substantially depending on the ambient conditions and the specific composition of the gasoline. Normally, the flash point is  -42 ºC and -23 ºC (-45 ºF and -9 ºF), as mentioned above.

Gasoline Fire Point

The temperature at which gasoline vapors can be ignited and sustain fire for at least 5 seconds, its fire point. Often, the fire point of a material is roughly 10 ºC above its flash point. So, for gasoline the fire point is roughly between -32 ºC and -13 ºC (-26 ºF and 8 ºF).

For a fire to start and be sustained only a very small area must have reached the fire point temperature, it is not necessary for the whole area to be heated. In fact, many fires start by the ignition of an extremely small portion of the gasoline vapors.

Since the combustion reaction causing the fire releases more heat (the reaction is said to be exothermic when it releases more heat than it requires to take place) the amount of vapors and therefore its pressure will rise with the increase in temperature.

Gasoline vapor can ignite without the addition of an ignition source if the temperature is increased past the fire point until the autoignition temperature.

Gasoline Autoignition Temperature

Under regular air and pressure gasoline spontaneously ignites at around 280 ºC (536 ºF). Gasoline can reach this temperature, for instance, if it is in contact with a hot surface, but if gasoline is highly pressurized it will heat and its possible for it to ignite as well.

What Happens To Gasoline When It Evaporates?

As gasoline is a mixture of hydrocarbons, and each different hydrocarbon has a different boiling point, when gasoline evaporates, hydrocarbons with lower boiling evaporate first. While the ones with higher boiling points will increase in concentration in the liquid.

The alkylbenzenes with three carbon alkylic chains are still present in most gasoline formulations up to 95% evaporated. However the alkylbenzenes with two carbons in the alkylic chain quickly evaporate completely.

What Fumes Are Released From Burning Gasoline?

The combustion of gasoline usually produces majorly carbon dioxide (CO2), along with carbon monoxide (CO) in smaller quantities. Carbon monoxide can lead to death if it is inhaled in high concentrations or for prolonged periods of time.

Gasoline Composition

Gasoline is composed of a mixture of many different hydrocarbons  (substances made of only carbon and hydrogen elements) with 4 to 12 carbon atoms in their molecules with varying proportions of each.

Alkyl benzenes are usually the most common class of hydrocarbons in most gasoline formulations. Other hydrocarbon classes commonly found include: olefins (alkenes), naphthene derivatives, and aliphatic hydrocarbons (alkanes and cycloalkanes).

Gasolines may also have substances containing sulfur (S), nitrogen (N), and oxygen (O) atoms in their structures in quantities smaller than 0.1% (by volume).

What Is An Aromatic Compound?

The majority of the hydrocarbons are hydrocarbons containing aromatic portions. An aromatic molecule or portion of a molecule is one that has the following chemical properties:

  • All or some of its atoms form a coplanar cyclic structure (made up of one or more rings).
  • The atoms forming the cyclic structure are making single and double chemical bonds in an alternate manner. This makes it possible for some of the electrons forming the chemical bonds to be ‘delocalized’.
  • The number of delocalized electrons must be even and not multiple of 4.

Gasoline Grades And The Octane Rating

Gasoline usually has three different grades, having lower or higher aliphatic hydrocarbons. In general, higher aliphatic hydrocarbon content translates into high octane rating, that is the gasoline has higher performance.

The specific  composition of the gasoline directly influences its performance. A commonly employed scale to address the performance is the octane rating. Gasoline can have an octane rating as low as 85 or as high as above 100.

The octane rating is not influenced by the number of carbons in the hydrocarbons in the gasoline but by their specific structure. For instance, the octane rating of isooctane (2,2,4-trimethylpentane) is 100, while the octane rating of normal octane is less than zero. 

Is It Safe To Transport Or Store Gasoline?

In this section, the main safety measures involving the transportation and storage of gasoline in day to day activities are presented.

Transportation

 Only listed, labeled, and approved containers with a cap are permitted to be used in transportation of gasoline. The following are safety measure involving gasoline transportation:

  • Don’t transport a large amount.
  • Use a proper gas can that is listed and sealed.
  • Ensure there is air ventilation.
  • Never transport a gasoline can in the passenger seat.

Storage

If to be stored in garages or sheds, gasoline must be inside an approved, labeled, and listed container with a cap. The following are recommended safety measures to adopt when storing gasoline:

  • Never store gas containers in or near areas where an open flame is or can be located. 
  • Also avoid contact of the gas container with any source of heat or electrical sparks (electric motors for instance).
  • Avoid leaving portable containers inside a vehicle or in the bed of a truck.
  • Never bring gasoline inside houses.

Is Gasoline Toxic?

Gasoline is highly dangerous if ingested. Additionally, gasoline easily produces vapors which can cause mild symptoms of asphyxiation. Below are some details regarding gasoline inhalation, ingestion and skin and eye contact.

What Happens If Gasoline Is Inhaled?

Gasoline has a characteristic strong odor, its odor threshold is around 0.025 ppm. In enclosed areas, gasoline vapors may cause asphyxiation.

Children are at higher health risks than adults.

Gasoline Ingestion Can Cause Death

For adults, severe intoxication can arise from ingestion of about 20 to 50 g and 350 g can lead to death. For children, 10 g may be fatal.

Possible symptoms of intoxication by ingestion of gasoline include:

  • Confusion and loss of consciousness.
  • Convulsion.
  • Drowsiness.
  • Hemorrhaging of internal organs.
  • Irritation to the gastrointestinal mucosa.
  • Pulmonary aspiration, which  can cause chemical pneumonitis.
  • Vomiting.
  • Vertigo.

Gasoline In Contact With Skin Or Eyes

If in contact with the eyes, gasoline vapors are mildly irritating. Liquid gasoline in the eyes can result in transient corneal injury.

Skin contact with liquid gasoline can cause irritation and dermatitis by degreasing the skin. Continuous contact with liquid gasoline for several hours can cause first- and second-degree skin burns.

What Are Gasoline Additives?

Additives are usually added in very low concentration (ppm range). They act providing oxidation stability, corrosion inhibition, demulsification, specific colors, anti-icing properties, and dragging decrease.

In the past decades the most common additive used in gasoline was tetraethyl lead ((CH3CH2)4Pb). Given the high toxicity of lead (Pb) this additive started to be gradually discontinued in 1976.

Gasoline additive examples include:

  • Butene (C4H8).
  • Ethanol (CH3CH2OH).
  • Methyl Tert-Butyl Ether (CH3OC(CH3)3).

Where Does Gasoline Come From?

Gasoline is a product of petroleum refining processes:

  • Petroleum crude oil is distilled and separated, by boiling temperature differences, in different fractions.
  • Cracking, branching/isomerization, and aromatizing of these fractions is performed.
  • Undesired  compounds. from the crude oil or produced in the above processes, such as sulfur and nitrogen containing compounds are removed by specific methods.

Before going in use some final steps are still required such as addition of additives and further purification.

Main Uses Of Gasoline

Gasoline characteristics should comply with the requirements of the engine in order to obtain the desired performance. The main use of motor gasoline is fuel for:

  • Automobiles.
  • Light trucks. 
  • Boats.
  • Recreational vehicles.
  • Power generators.

Conclusion

In this article the answer to the question, ‘’Is Gas Flammable?’’ was answered considering gas the same as gasoline. Further insight into gasoline fire related properties were presented. Some information regarding gasoline toxicity was also provided.

Frequently Asked Questions (FAQ): Is Gas Flammable?

Is gasoline flammable or inflammable?

Gasoline is flammable and inflammable. Flammable and inflammable have the same meaning, however the use of the word inflammable is highly discouraged given its potential misinterpretation.

Is gasoline the most flammable?

Although highly flammable, gasoline is not the most flammable material  out there.

Can gasoline ignite without a spark?

Yes, gasoline can ignite in absence of a spark or a flame. The exact conditions depend on factors such as the pressure and the oxygen content in the air, as well as the presence of other materials that could increase the chances of gasoline catching on fire. When gasoline reaches its autoignition temperature it will spontaneously ignite.

Is gas flammable or explosive?

Gasoline is both flammable and explosive. Gasoline is considered flammable because its vapors can be ignited if in contact with an ignition source at low temperatures. The explosive limits of gasoline are around 1.2% to 7.1% by volume in air.

What type of gas is flammable?

All gasoline types (or grades) are flammable.

What gas is not flammable?

In the case of gas meaning a substance or mixture in the gaseous phase, there are many examples of nonflammable gases. The prevalent gas in the atmosphere nitrogen (N2) is not flammable. Water in gaseous form is not flammable. Oxygen gas (O2), although present in most fires, is not flammable.

References

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M.A. Kamrin, Gasoline, Editor(s): Philip Wexler, Encyclopedia of Toxicology (Third Edition), Academic Press, 2014, Pages 700-701, ISBN 9780123864550, https://doi.org/10.1016/B978-0-12-386454-3.00391-2. (https://www.sciencedirect.com/science/article/pii/B9780123864543003912) (Accessed June 23th, 2022)

E. Lois, E.L. Keating, A.K. Gupta, Fuels, Editor(s): Robert A. Meyers, Encyclopedia of Physical Science and Technology (Third Edition), Academic Press, 2003, Pages 275-314, ISBN 9780122274107, https://doi.org/10.1016/B0-12-227410-5/00268-4. (https://www.sciencedirect.com/science/article/pii/B0122274105002684) (Accessed June 23th, 2022)

https://www.eia.gov/energyexplained/gasoline/ (Accessed June 20th, 2022)

https://www.nfpa.org/News-and-Research/Publications-and-media/Blogs-Landing-Page/NFPA-Today/Blog-Posts/2021/05/13/Stories-of-gasoline-hoarding-raise-fire-safety-concerns (Accessed June 23th, 2022)

https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=30 (Accessed June 23th, 2022)

https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=465&toxid=83 (Accessed June 23 th, 2022)

http://wyomingworkforce.org/_docs/osha/toolbox/facts-about-gas.pdf (Accessed June 30th, 2022)

https://www.medicalnewstoday.com/articles/323426#Burning-gasoline-releases-several-harmful,a-prolonged-period-of-time. (Accessed June 30th, 2022)

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