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Whoa.
What just happened???
Let’s watch that again.
What you’re seeing is called flame jetting.
It requires a perfect storm of circumstances, but pouring gasoline or some other fuel from
a container can shoot out a ten-foot jet of flame.
This has happened.
People have been seriously burned, and in some cases they HAVE died.
So just to be clear: We at Reactions did not make these videos.
They were produced by trained professionals from the ATF at their Fire Research Lab.
In other words, we didn’t try to make flame jetting happen, and neither should you.
Part of the reason flame jetting is so dangerous is that we have certain expectations of how fire normally behaves.
Those expectations do not include shooting out of a small container and engulfing a victim 10 feet away.
The ATF set out to investigate how this happens.
How do the flames jump like this?
Why doesn’t the liquid just burn without jetting?
And how do we prevent flame jetting from happening?
The good news is, for flame jetting to occur, the circumstances have to be exactly right.
First, the bottle needs to have room for air above the fuel.
Fuel evaporates into this space and mixes with the air, making a potentially flammable
mix of fuel and oxygen.
Second, that mix has to be in balance.
If too much fuel evaporates, it crowds out most of the air and the mixture won’t burn.
This is the case with fresh gasoline.
But older, “weathered” gasoline -- gas that’s been sitting around for a long time
-- evaporates much more slowly, so it could burn.
Most fuels don’t need to be weathered like this - alcohols, for example, evaporate at just
the right rate to produce a flammable mix no matter how long they’ve been sitting around.
Third is the bottle itself.
The neck of the bottle needs to be wide enough to let the mixture of fuel and oxygen out
where it will be exposed to the flames.
But it can’t be too wide, or there will be no vapor buildup and no jet.
So, for example this measuring cup - not gonna jet.
So here the ATF is pouring a partly empty, narrow-necked bottle of fuel over a fire.
Two things are gonna happen.
First, some of the gasoline vapors come out of the container and air rushes in.
Oxygen enters, and the space is primed to burn.
Second, the vapors falling out of the container ignite, leading the flames into the container.
Then, the gases ignite in a good ol’ combustion reaction, where hydrocarbons and oxygen become
CO2 and water, releasing a ton of energy.
That drives the temperature up, so the gases expand and the pressure in the container increases,
which forces the remaining liquid to come out as millions of tiny droplets.
Those droplets and the vapors coming off of them create the flame jet.
All of this happens in a split second.
You cannot dodge this.
But you can prevent flame jetting in the first place.
First, don’t pour flammable liquids anywhere near open flames or, you know, any ignition
source… please!?
Any flammable liquid in a narrow-necked container could potentially jet -- and that does include
liquor bottles at your friendly neighborhood watering hole, as well as all of these things
you might have around the house.
There is one more thing you can do.
Here’s a container with a neck and plenty of air space pouring alcohol over a flame,
but there’s no jet.
So what's going on? Look closer -- there's this little mesh dealio over the opening.
It's called a flame arrestor.
These little guys do seem to prevent jetting by stopping flames from getting into the container.
So they’re a useful precaution as well.
But the best thing you can do is not put yourself in this situation in the first place.
Just don’t mix fire and flammable liquids.
Stay safe out there.
Huge thanks to Adam St. John and the ATF for their help with this video.
Also, Thank you to CuriosityStream for supporting PBS Digital Studios.
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We’ll see you next week.