If there’s one thing that everybody knows more about in the last 10 years than they ever did before, it’s pollution. And if there’s an image that’s used to illustrate the potential destruction of our environment more often than a bunch of burning tires, I’d be hard pushed to name it. So, are tires a massive fire risk? Do they really just catch fire all over the place or are tire fires something a little more sinister than we’re led to believe.
Tires are not particularly flammable in that they need to be heated to 750 degrees Fahrenheit (400 Celsius) for several minutes in order to ignite. However, once they do catch fire, they can burn for a long time and produce some very toxic smoke.
Many people would assume that tires are very flammable, but that depends on your definition of flammability. Let’s take a closer look at tires and their fire hazard risks. Here’s what you need to know.
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Also read: What Makes Something Flammable?
Can Tires Catch On Fire?
Yes, tires can catch on fire. And they can burn for a long time when they do.
They wouldn’t use burning tires as the shorthand for pollution if they couldn’t catch on fire.
The thing is; however, they aren’t all that flammable. They are not easy to ignite.
You can’t just drop a match on a tire and expect it to combust. In fact, it’s incredibly difficult to light a tire on fire under normal circumstances and you really have to be trying in order to make one burn.
The big problem with tire fires is not getting them started – it’s how they behave after they’ve started.
Also read: Is Rubber Highly Flammable?
Are They Combustible?
Yes, tires are combustible but to get one to combust you will need to heat it to about 400 degrees Celsius (that’s 750 degrees Fahrenheit) and then keep it at that temperature for a few minutes in order to ignite.
That means you need to heat the tire for several minutes at a temperature of more than 4 times that of boiling water before you can burn it.
That’s not very combustible and it explains why, despite rumors to the contrary, you’re not going to find tires suddenly bursting into flame by themselves.
They can’t and there’s not enough energy in sunlight to come remotely close to creating that kind of sustained heat, if there was – there would be no life, as we know it, on the planet.
Also read: Is Polyurethane Flammable? It Depends…
How Long Do These Fires Burn?
Tire fires are notorious for burning for a very long time and being difficult to extinguish. This is because they contain a ton of fuel (hydrocarbons) in the materials used to make tires.
Just take a look at this giant tire fire that burned for 17 days:
Despite the commonly held belief that tires must burn for periods of years or more, it’s entirely possible to burn tires quickly in a fast-burning fire with plenty of heat and oxygen.
The time burning will depend on the fuel loading (amount of tires to burn), ambient temperature and humidity, wind patterns, and a variety of other factors. But they don’t always burn for a very long time.
One tire burning by itself can burn for a while, but not days. It will run out of fuel to burn.
But there are also countless incidents of tires burning for days, weeks, months… even years?
This video goes into detail about the Virginia Tire Fire Story that burned 7 million tires and lasted for 9 months:
Also read: Is Tar Flammable?
Can They Burn For Years?
If a tire burns through a process known as pyrolysis, it can take its sweet time. There have been known instances of tires burning like this for more than a decade at a time – in Heyope in Wales, 10 million tires burned for, at least, 15 years.
This is one of the reasons that burning tires are so often used to illustrate pollution problems – it’s very easy to find a tire fire that’s constantly burning to take pictures of.
Unfortunately, this kind of fire is really bad news for people and the environment. The smoke contains carbon monoxide, sulfur dioxide, styrene, butadiene, and cyanide.
All of these chemicals are highly polluting and many of them are highly toxic too.
So, why is it that these fires are left to burn for a decade or more when they’re so polluting? Well, it’s because they’re super hard to put out.
How Do You Put Out These Fires?
Tire fires are among the most difficult fires to extinguish because of the way that they burn. We noted that you have to heat a tire up for a prolonged period of time before it will burn and that’s because the “thermal conductivity” of a tire is lousy.
What that means is it takes a lot of heat to warm a tire up all the way through, but once it’s warm? Well, then it takes a lot of cooling to cool it back down again because the heat finds it just as hard to leave the body of the tire as it did to get in there in the first place.
Worse, if you put out the tire fire so that it appears to be no longer burning, there’s a high percentage chance that you just put the fire on the outside of a tire out – inside, it’s still burning, give it a little while and it will burst into flame again.
You can smother tires in sand to remove oxygen supply to the fires, but this requires a lot of sand and when you’re talking about thousands of tires on fire, it’s not practical.
Firefighters may use firefighting foam to create a blanket that seals the oxygen from the fuel (tires) to smother it, as well as to try to prevent it from re-igniting. There are also some other specialty extinguishing agents that can help with these types of fires.
Here you can see that even when special extinguishing products are used, it is still tough to put out a tire fire:
What Class Of Fire Is A Tire Fire?
A tire fire is a class A fire and thus, you can, in theory, extinguish it with water, sand, etc. but as we’ve already seen a big tire fire is hugely challenging to extinguish.
The 4 classes of fire are:
- Class A – Ordinary Combustible (wood, paper, plastic, rubber, fabric)
- Class B – Flammable Liquids (gasoline, kerosene, acetone)
- Class C – Energized Electrical (fires with flowing electrical current)
- Class D – Flammable Metals (magnesium, titanium, lithium)
- Class K – Cooking Oils (vegetable oil, lard, grease)
Note: This applies to the U.S. There is a different fire class system used outside the United States.
Also read: How Do You Put Out A Magnesium Fire?
How Hot Do These Fires Get?
A tire fire burns at temperatures of over 750 degrees Fahrenheit, since this is the minimum temperature to get most tires to ignite, it will be at least this hot, usually much hotter.
Molten rubber from burning tires is very hazardous to human health and the smoke is toxic.
At What Temperature Do They Catch Fire?
A tire catches fire at 750 degrees Fahrenheit (400 Celsius), but it must be at this temperature for several minutes before ignition is possible due to the thermal resistance of the rubber.