A quick question about FIRE

[David Evil Overlord]

A character is using an empty fire extinguisher as an improvised shield.

He is being attacked by a super villain who is trying to set fire to part of his anatomy he really doesn't want her to burn.

Is it possible for her to:

A) use her fire-based super powers to heat up the extinguisher so he (a non-super-powered mere mortal) can't hold it and has to drop it?

and

B) heat it up without making it explode (aerosol cans must not be incinerated, fire extinguishers, I don't know)?

I want to have A happen, not B. But I need to know if it will work that way.

 

[HareBrain]

Non-expert here, but: fire extinguisher canisters are able to cope with huge pressures. The increase in pressure of the air inside an empty extinguisher caused by heat would be a tiny, tiny fraction of the pressure of the contents it was built to hold in the first place. So yes, perfectly possible, I'd say.

I now await contradiction by someone who knows what they're talking about.

 

[Dave]

My daughter went to the Reading Festival a few years ago. Apparently, at the end of it, it is traditional to set fire to tents, clothes, anything that will burn, and even some things that will not burn. Someone in the field where she was camped made a huge bonfire and threw the fire extinguisher on it. The Fire Brigade arrived, the area was cordoned off, and everyone told to pack up their tents and move away for Health & Safety reasons. I know it isn't a scientifically conducted experiment, but if it helps, she said that the fire extinguisher never exploded.

 

[Mirannan]

There's a big difference between an empty fire extinguisher and a full one. A full one usually has some liquid or other inside it, and heating that up will generate huge pressures as the liquid "tries" to boil. Your B is probably possible, because air doesn't do that.

As for being able to heat up a non-flammable item such as a fire extinguisher, it depends on how the pyrokinesis works. If it works by pumping energy into whatever it is you are trying to burn, then A should work. However, there is another way fire powers might work. (Science geek hat on)

The only reason why anything flammable in air doesn't instantly burst into flames is because the reactions involved in fire have something called an "activation energy"; energy has to be put in for the reactions to start. Of course, once started the energy coming from the flames is enough to keep this going. In fact, there are a considerable number of substances that do burn spontaneously in air, cesium being one of them - in these cases the activation energy is low or absent.

So, it's possible that fire powers might work by lowering this energy barrier, in which case A won't work.

It's up to you. Decide how the powers work (telling the reader how is up to you, but it probably isn't relevant to the story) and then you'll know.

 

[prizzley]

A character is using an empty fire extinguisher as an improvised shield.

In an ideal world, there wouldn't be an empty fire extinguisher. H&S demands regular checks in commercial premises. Fire extinguishers are dated when checked and replaced before their expiry date. If used - and their sole purpose to extinguish flames on an exit route to enable people to escape the building - they would be replaced. That's not to say a commercial one couldn't be dumped.

Dunno about about the weight of an empty one, but a full one (full-sized) weighs a ton. You need panic-induced adrenalin to heft one, and you wouldn't want to hold it long. On my try, supervised by a fireman after his safety talk, I couldn't lift one.

 

[AMB]

Are fire extinguishers flammable? I know some contain flammable gas, but I was wondering more on the pressurized cannister thing.

If the character is using it as a shield after emptying it onto the fire, it might help you to know what sort of fire it is and whether it was the right one for the job (and if the pressurized cannister thing is only relevant dependent on context, whether using it as a shield is a mistake).

 

[Kylara]

Fire extinguishers are designed not to explode - lots have pressure valves so that they don't - they let out the increased pressure slowly...they can go to 500psi internal pressure so heating up the outside of an empty extinguisher probably won't get the air to that pressure, and if it does then the pressure release valve should come into play...also depending on the extinguisher type it will have a specific pressure max and will either have or not have a release valve. Extinguishers also don't tend to explode in the conventional way, they will rupture at a weak point (normally near the top) rather than exploding in a bomb style way

 

[Ursa major]

How is the fire extinguisher being held?

If there are no handles on the back, at least one of the hands will be visible, and so, presumably, this will be vulnerable to the fire-based power. And as the person only has two hands, he can only swap hands the one time, before he has the two of them roasted.

 

[David Evil Overlord]

The victim has just emptied the extinguisher onto the fire that's blocking the exit.

The super villain who started the fire is able to throw fireballs so big you couldn't use a fire engine as a shield. Not for long.

BUT, she's toying with him.

 

[jastius]

wouldn't it also matter whether it was a powder filled type or a foamy filled type. powder is used for an ABC fire and is kept in places with electronics. the foamy type would have a propellant which could be pressurized.
if it was me as soon as the extinguisher got hot I would pitch it at her face.

 

[paranoid marvin]

How is the fire extinguisher being held?

If there are no handles on the back, at least one of the hands will be visible, and so, presumably, this will be vulnerable to the fire-based power. And as the person only has two hands, he can only swap hands the one time, before he has the two of them roasted.

I hope you're talking about his hands there!

 

[David Evil Overlord]

wouldn't it also matter whether it was a powder filled type or a foamy filled type. powder is used for an ABC fire and is kept in places with electronics. the foamy type would have a propellant which could be pressurized.
if it was me as soon as the extinguisher got hot I would pitch it at her face.

She's a little bit tougher than your average person. He's already tried punching her, and hurt his hand. Then he hit her in the face with the extinguisher, and all that did was split her lip and annoy her.

 

[Harpo]

How about a change of tactics? Where there's a fire extinguisher there ought to be other things, including water pipes? Use the fire etinguisher to smash open the water pipes, then fight fire with water.
As for protecting a certain part of the anatomy, can't he turn around first and soak himself before he fights back?

 

[David Evil Overlord]

I don't know if wetting his pants can be seen as heroic.

The villain wants the cinema to burn, along with everyone inside. She's sabotaged the sprinkler system and water pipes. She left a couple of extinguishers since she couldn't get to them without being seen.

But there is still one other thing he could use...

 

[Biskit]

My daughter went to the Reading Festival a few years ago. Apparently, at the end of it, it is traditional to set fire to tents, clothes, anything that will burn, and even some things that will not burn. Someone in the field where she was camped made a huge bonfire and threw the fire extinguisher on it. The Fire Brigade arrived, the area was cordoned off, and everyone told to pack up their tents and move away for Health & Safety reasons. I know it isn't a scientifically conducted experiment, but if it helps, she said that the fire extinguisher never exploded.

As various people have pointed out, fire extinguishers are designed to cope with serious internal pressure. The problem (and I would guess this is what the fire brigade were worried about) is if the heat damages the casing and allows it to rupture. There is also the other worry with a 'fully loaded' fire extinguisher (or any other pressurised gas cylinder) that the valve assembly lets go abruptly and the beast goes off like a rocket.

Back in my days working in a lab, gas cylinder safety really had two aspects. What to do if the stuff inside was nasty and got loose, and how to minimise the chance of a cylinder toppling over and shearing off the valve head. A fully laden nitrogen cylinder (maybe shoulder high on me, and I'm just under 6') with its valve gone was described as a torpedo. The advice given at the time: if you were in the lab and this (rare) event should happen, try to get out of the way and hope if finds a weak spot in one of the walls.

So, if the arch villain really wants to ruin the hero's day, don't just heat the fire extinguisher, concentrate the heat somewhere useful and make the thing go pop. It does not take much to make pieces of metal go far and fast.