Oil is everywhere and not just motor oil or big oil. We use vegetable oils in our food, mineral oils in everything from furniture polish to heavy industry. We burn them, we cook in them, we lubricate with them, and they’re super useful. And as we all know, some oils can burn very easily, but is this true of all oils or are we overestimating the risk that oils present to us?
Most oils can catch fire but are not technically considered to be flammable. This is due to the OSHA standard that states flammable liquids are those that have a flashpoint at or below 199.4 degrees Fahrenheit (93 Celsius). Many oils can still present fire hazards though.
Let’s take a closer look at different types or oils and their ability to catch fire. Check it out.
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Also read: What Makes Something Flammable?
Which Oil Is Most Flammable?
This is akin to the question “how long is a piece of string?” There are so many oils in use and so many different blends of oil, as well as potentially undiscovered oils – you can’t say “that oil is the most flammable.”
Of course, as oils aren’t technically flammable – the technically accurate answer is “none of them”.
OSHA (1910.106(a)(19)) states that any liquids that have a flashpoint at or below 199.4 degrees Fahrenheit (93 Celsius) are flammable and others are not. Even if those liquids (like most oils) can still catch fire.
Flashpoint is the temperature at which a liquid emits enough fumes (flammable vapors) to ignite with a spark or flame.
Though that is just a technicality because most oils will catch fire if the temperature is high enough.
However, that’s not a very satisfactory answer and so, we’re opting for the simplest answer, which was to look for the oil with the lowest flashpoint in common use.
Coconut oil can be considered the most flammable cooking oil. It has a smoke point of around 385 degrees Fahrenheit (196 Celsius) and a flashpoint of 563 degrees Fahrenheit (295 Celsius).
Coconut oil burns well enough that it can even be used as a fire starter:
In fact, it means that while coconut oil can be used to great effect in cookery, it can’t be used to fry foods in because it’s too easy to set on fire and burned oil makes your food taste terrible.
However, 385 degrees Fahrenheit is not a very low temperature and coconut oil won’t catch fire easily in other circumstances. So, don’t worry about rubbing it into your hair or using it as a base for a homemade makeup experiment, it’s not going to burst into flame while you’re wearing it.
There are other oils that are more flammable then coconut oil, but used in other applications.
Motor/engine oil has a flashpoint of 300 to 400 degrees Fahrenheit (150 to 205 Celsius). This means it still doesn’t fit the standard as a flammable liquid, but it is easier to catch fire than many other oils.
For more information on motor oil and its flammability, read this article.
An exception is essential oils. These fragrant oils can catch fire at even lower temperatures, but they seem to vary based on the carrier oil used. Some even have a flashpoint of about 100 degrees Fahrenheit, which makes it a true flammable liquid.
This doesn’t mean that you should be completely careless about using oils in your home.
They should be stored properly because oil fires are difficult to tackle and burns from liquid oil are particularly severe. While the smoke points and flashpoints of most oils are high enough that they won’t spontaneously combust, in their containers, they can catch fire with relative ease near cooking flames, etc.
Also read: Is Olive Oil Flammable? Can it Catch Fire?
Other Oils That Can Catch Fire
No oils in common usage, or that we are currently aware of are technically flammable, except some essential oils. However, almost all can catch fire at higher temperatures.
You shouldn’t ignore oil that is smoking as it has reached its smoke point and is getting closer to the point at which it could ignite.
Mineral oils are, generally, slightly less combustible than cooking oils. But they should both be stored appropriately and kept away from naked flames when they’re in use.
Which Are Not Flammable?
All oils are not flammable, because of the flashpoint being above 199.4 degrees Fahrenheit.
But remember this doesn’t mean that they can’t catch fire. Most oils that I am aware of will catch fire at high temperatures.
Also read: Is Mineral Oil Flammable? Yes and No…
Why Is It So Flammable?
Oils can sustain fire well because, whether they are mineral or vegetable, they contain lots of hydrocarbons. Hydrocarbons are the basis of most fuels because they burn pretty easily.
The hydrogen and carbon bonds are not very strong and when they are exposed to a heat source of sufficient strength, they will break apart.
When they do this, they will release carbon and hydrogen. These will burn in the presence of oxygen and the carbon will become either carbon dioxide (the gas that we exhale) or carbon monoxide if it doesn’t burn fully. Carbon monoxide is a problem if it’s produced in large quantities and it can kill.
Hydrogen, on the other hand, burns in oxygen to produce water. And both the carbon and hydrogen reactions are exothermic – that means they release heat when they take place.
This heat helps to spread the fire within the oil and so, once oil starts burning, it’s quite hard to put the blaze out because it’s self-sustaining.
Also read: Is Vegetable Oil Flammable? Technically No…
Does It Actually Burn In A Fire?
Yes, oil will burn in a fire. In small quantities, the byproducts will be carbon dioxide and water and this isn’t going to be a problem.
However, in large quantities, you may find that the oil starts to release large amounts of carbon monoxide and this is potentially deadly.
If you find that an oil fire gets out of hand and you don’t feel it’s safe to try and extinguish the blaze, the best thing to do is call the fire department and wait for them to come and put it out.
Don’t, whatever you do, hang around and breathe in the fumes.
Also read: Why Are Doritos Flammable? Let’s See…
Can Cooking Oil Spontaneously Combust?
Most cooking oils can spontaneously combust (ignite without the presence of a spark or flame) if they get hot enough to reach their auto-ignition temperature.
However, it has to be under the right circumstances. Cooking oil doesn’t just set fire to itself in the bottle. If it is dried up with a rag though, there are certain exothermic reactions that take place as the oil dries.
The release of heat from this process can potentially catch the oil and the rag (and then whatever the rag is being stored or disposed of in) on fire.
This video talks about house fires that have started with linseed and other oil-soaked rags that spontaneously caught fire:
It’s important not to throw away rags into the standard garbage that has been used to mop up oil spills and you should never put them in the dryer, either.
Also read: Is Grease Flammable? It Depends…