Are aerosol cans flammable? (A 5-point guide)

This article will answer the following question: “Are aerosol cans flammable?”. We will discuss the dangers of aerosol cans, investigate if and in which conditions they might be flammable, and other pertinent issues.

Are aerosol cans flammable?

Yes, they’re highly flammable. Aerosol cans are made of metals that are normally not flammable, but they might contain under-pressure flammable vapors that can be very fire hazardous. Even if the can appears to be empty, we can’t assume it really is.

What is aerosol?

We normally name products as aerosols when they can push aerosols out of a can.

An aerosol is a suspension of fine solid particles or liquid droplets, normally in the air. Effectively, we can say that aerosols are thin solid particles suspended in the air.

We often believe that anything in its powdery form can be flammable, or at least combustible, but it’s not so simple.

Aerosol is not a thing, is a class of things. Is a specific physical state a certain substance can present itself at some point.

For example, we input aerosols into the air every time we sneeze.

Commercially, we name aerosol any kind of canned gas.

Aerosols are used due to the rapid mechanism of action. A can of an aerosol is normally the only tool required to use. After applying it, its solvents will fly away, and then the job is done. But this easiness often comes with a price: flammability.

Aerosol properties

Aerosols can be made of many things. 

For example, organic molecules, sulfates, nitrates, mineral dust, and sea salt are things that can become airborne in the form of an aerosol. Each has its own associated risks for health and the environment.

The action of aerosol substances happens by applying the product to a certain surface. 

Some of the ingredients will remain or stick to the surface, others will evaporate in the air. Propellants, for example, don’t do much besides carrying other compounds into a surface. 

But all aerosol ingredients are equally important to the final product.

Aerosol products formulas are created considering 4 basic components: 

  • Active ingredient(s), are the things that have active participation in the labor that’s being done;
  • Solvents, which are substances in bigger quantities, are often required to mix the active ingredient, or dissolve something else in the region that’s being applied;
  • Propellants are gases used to carry the other ingredients out of the can. Normally, they will dissipate right after squeezing the can’s button.
  • Binders. These molecules play secondary roles, acting like binding agents that make the other ingredients mix while inside the can.

All these ingredients combined can formulate the mist, dust, fume, smoke, or fog that comes out of the can. Some compounds used in aerosols may possess more than one functionality.

The composition of an aerosol flask may vary, but it’s essentially made with a metal can, a valve, and a button.

The reason why they’re made of metal is that metal can sustain pressure. In an eventual mechanical shock, the material will bend before breaking. The flasks can’t suffer much oxidation, so they can’t burn as well (combustion is a reaction with oxygen).

The U.S OSHA

OSHA (the United States Department of Labor) classifies flammable aerosols in two categories:

  • Category 1: Extremely flammable substances.
    Substances that contain over 85% flammable components, and that the heat of combustion is bigger or equal to 30kJ/g. Spray and foam aerosols are included. There are also other properties like flame duration and height.
  • Category 2: Flammable substances.
    Substances that contain around 1% or more of flammable components, or that the heat of combustion is bigger or equal to 20kJ/g. It’s valid for spray and foam aerosols as well, each having its criteria

Flammability

Aerosol products are often associated with high and extreme flammability and explosions. How flammable a certain content of an aerosol can will depend on its ingredients. 

Although, the ingredients alone can only satisfy part of the answer because substances can behave differently according to the mixture.

Also, the specific composition of most aerosol products is a trade secret. The companies usually present a range of values for each ingredient at best.

Nevertheless, by knowing which solvent is used in each formulation we can assume rather an aerosol substance can catch fire or not.

But there’s another and more reliable way to understand if an aerosol product is flammable or not: its Safety Data Sheet (SDS). This is a document that compiles all relevant information regarding the safety of a product, under a set of conditions. 

The easiest way to find SDS is to simply google the product’s name followed by the words “safety data sheet”, or simply “SDS”. If you feel that there’s too much information on it, try localizing the word “flammable” or “flammability” in the document.

But of course, we will always be here to assist you.

The same compound can have different safety information bound to it, depending on if it’s meant to be used domestically or industrially, for example.

Aerosol cans

Components inside an aerosol can are normally flammable.

Adhesives, bug sprays, solvents, cleaners, varnishes, paints, and many others normally contain flammable compounds. 

Some of them may adhere to the inside of the can, so it doesn’t matter if the can looks empty or not: it can always be flammable.

Can overheating

You can never safely heat an aerosol can. There will always be a fire hazard attached to this action.

For example, you must not leave an aerosol can in the sun, inside a car, a hot machine, or placed anywhere near a heat source. The gas inside the can will raise its temperature, try to expand, and eventually find a weak spot in the can valve.

The pressure inside the can will quickly escape from that weak spot. Since the gases are normally flammable, and the can is already hot, there’s a big risk of explosion by heating a can, even if it appears to be empty.

Can piercing

Any disposable aerosol can never be pierced or reused.

A rupture in an aerosol can is always bad. Highly volatile organic compounds may be set free, unleashing hazardous gases for our health and really big fire hazards.

Also, the danger of piercing, rupturing, or damaging a can is not only present by doing it on purpose. 

If your labor or hobby requires the use of any kind of force, machinery, tools, or heat of any kind, an object can always fly off and reach the can. This could even happen in a harmless parking lot that has gravel on the ground.

Can impacting

Especially during transportation, aerosol cans may be easily knocked over, dropped, or impacted by passing machinery and vehicles, which could leak their content.

When a can burst, it can also become a projectile that can really harm people, animals, and infrastructures. Besides, the can itself can fly to another ignition source that’s not so close by.

Cold burns

Another important danger an aerosol can possess is the possibility of inflicting frostbites, in an eventual leaking.

You have probably already noted that when we squeeze the button of a can, the can gets colder. This is because the gas steals energy from inside so it can burst, in something we call adiabatic expansion.

This happens because the process of leaving the can happens too quickly, so both the aerosol can and content have no time to heat, using the surrounding energy (also in the form of heat).

So, since the spraying happens quickly, the gas comes out cold (and can get colder if you keep squeezing the button). Likewise, the can itself gets cold, and it takes some to heat again.

If a can gets pierced, especially big ones, it will rapidly lower its temperature. Sometimes it’s even possible to see the can freezes because the air moisture can condense around it, forming ice.

This is the main reason why you can never hold a leaking can with your bare hands. It may cause severe cold burnings on your skin.

Conclusion

Aerosol cans are not flammable themselves, but their content is normally highly flammable. It doesn’t matter if the can looks empty, it can still burn. If an aerosol product fits under the flammability category of 1, the danger is even worse.

Aerosol cans must never be damaged, heated, left in the sunlight, or emptied too quickly. When a flammable compound it’s in aerosol form, it is the most flammable scenario possible, especially if it’s under pressure.

Frequently Asked Questions (FAQS): Are aerosol cans flammable?

Are aerosol cans easily recyclable?

Yes. Aerosol cans are usually made from steel or aluminum, which are metals that have high recyclability. 

Aluminum recycling is tremendously good for the environment because the mining process is very hazardous to the environment. Recycling aluminum usually requires only 5% of the energy needed to extract it from the soil.

Are aerosol cans bad for the environment?

The gases trapped inside the cans are normally hazardous to the environment. Besides, the metal cans themselves are considered hazardous waste because there are still remainings of the products inside, which are normally hazardous.

Although, this is only true if the cans are incorrectly discarded. Industries appreciate recycling aluminum overall because they save a lot of money by doing so. Recycling is good for everyone.

Are aerosol cans hazardous waste?

They can be considered hazardous waste if there’s still content inside.

Many aerosol products use ingredients that are really bad for the environment, even in low concentrations, so the cans that hold the compounds can be considered hazardous as well.

Citations

https://en.wikipedia.org/wiki/Aerosol
https://en.wikipedia.org/wiki/Aerosol_burn
https://en.wikipedia.org/wiki/Adiabatic_process
https://www.schc.org/assets/docs/ghs_info_sheets/schc_osha_flammable_aerosols_approved_3-22-16.pdf
https://www.justrite.com/osha-violations/aerosol

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