There is no single compound that is “tar”. However, we all know that black or dark brown, highly viscous and distinct smelling liquid that we consider to be “tar”. It can be made out of wood, peat, coal, or as a byproduct of petroleum distillation. But is the use of tar a risky business beyond getting sticky and are we introducing a fire hazard into our lives when we use tar?
Tar is usually flammable, but its ability to ignite and catch fire will depend on what kind of tar it is. The fumes or vapors that tar can give off will catch fire very easily and can be dangerous.
Tar can be a fire hazard, depending on the type and situation. This is what you need to know.
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Also read: What Makes Something Flammable?
Table of Contents
What Is Tar?
Tar is a thick fluid that contains hydrocarbons (compounds made of both hydrogen and carbon) as well as some percentage of “free carbon”. It is made by a process known as “destructive distillation” and from any hydrocarbon source including peat.
It may also be referred to as “pitch” or “asphalt” (though asphalt is often called “mineral tar” or “mineral pitch” too).
Pitch tends to be a little thicker than the substance called “tar” in building projects and road construction and is better at building solid “viscoelastic” end products.
Tar can occur naturally, the most famous location in the United States for natural tar is the La Brea Tar Pits outside of Los Angeles, for example.
There is also a product known as “wood tar” which was produced from pine wood, and which has similar properties to mineral tars.
It was mass-produced in Europe for a long period of time because it was an excellent sealing agent for ships and sailing vessels to prevent the wood from rotting.
Today, it is made in small quantities for use in traditional boats but the huge industry producing “wood tar” is long gone.
How Is It Used?
Tar has a surprisingly wide range of applications. It’s been used in shampoo (coal tar) to protect against psoriasis, for making roads, for waterproofing (not just in boats but also churches and roofing), for protecting the exterior of buildings, for flavoring candles, as a spice for food, for a sauna scent, and in cosmetic products too.
It was also once used for a very unpleasant punishment. “Tarring and feathering” was achieved by pouring hot tar on the victim and allowing it to cool, which would freeze the person in place, and then feathers were added to make the process more humiliating.
The victim would be left as a public example for the day before the tar was cracked and removed.
This practice ended because it would leave severe burn scars due to the application of hot tar in the skin.
Does Tar Catch On Fire?
Tar is flammable and it will catch light if the fumes are exposed to a spark or naked flame and it won’t take a lot of effort to set fire to liquid tar, either.
It may also spontaneously combust if left to sit on rags, etc. and it’s important to safely dispose of any rags used to clean up tar spills.
What Happens If You Set It On Fire?
One peculiar property of tar is its viscosity and when tar catches fire it will start to become less viscous (runnier) and foam up, this will cause it to quickly rise up inside the container it is in and potentially, depending on how much tar is present, start pouring down the sides of that container – while burning.
Tar doesn’t present much of a risk of an explosion but this change in volume can make it a more dangerous fire hazard than many other substances.
Why Is Burning Tar So Sticky?
Burning tar is sticky because of the motion of the molecules within the tar. It allows for the viscous liquid to become more elastic, and that property also makes it sticky.
It’s a good idea not to get burning tar on your skin for this reason.
Is Coal Tar Flammable?
Yes, coal tar and coal pitch are both considered to be flammable and dangerous fire hazards.
You should store them according to the instructions on the material safety data sheet and use them accordingly too.
Is Road Tar Flammable?
Road tar is not as flammable as some forms of tar, but it is still considered to be combustible, which means you should still keep it away from flames except when using the flame to melt the tar onto the road.
What About Dry Tar?
Yes, dry tar is highly flammable and is even something of an explosion hazard due to the ability of the tar to react violently with strong oxidizing agents.
Roofing tar is combustible, not flammable though if it is converted into a vapor, it will be flammable.
Are Tar Fumes Dangerous?
Tar fumes are a minor inhalation hazard, and they can irritate your respiratory tract.
This means that if you have asthma, for example, it’s best not to work with tar under any circumstances.
In most cases, however, you will be fine if you don’t inhale very much and immediately move away from the tar and go outside when you do inhale some.
If you were to inhale enough tar, it would cause choking and eventually asphyxiation and death but given the acridity of tar smoke, you should have moved away long before this becomes a possibility.
Is Tar A Carcinogen?
Yes. The tar produced by cigarettes is chemically similar to other tar and it can coat the inside of the lungs, over time this can lead to permanent damage to the lung and it may cause cancer or other health problems such as emphysema.