I see people do things with fire extinguishers in TV shows and movies sometimes that don’t make sense to me, based on the fire extinguishers that I have experience with.
I wonder - is this Hollywood/Canada movie magic, or are there fire extinguishers I don’t have experience with (and can’t find on the Internet) that actually freeze the fire?
[ul][li]In one show, a character used the blast from a fire extinguisher to freeze a door, which he then kicked through with his foot.[/li][li]In another, several characters used fire extinguishers to freeze padlocks, which they then knocked off with a casual swipe from the extinguisher.[/li][li]Finally, I saw some characters lower the temperature of some small beings with blasts from the extinguishers. Their goal was to get them safely to 51 degrees, and apparently the extinguishers did that.[/li][/ul]
So - are there any actual extinguishers that do that?
Yep, CO2 fire extinguishers get very cold. CO2 extinguishers contain carbon dioxide, a non-flammable gas, and are highly pressurized. The pressure is so great that it is not uncommon for bits of dry ice to shoot out the nozzle. They work great for B and C type fires, which are grease fires and electrical fires, respectively. They don’t work very well on class A fires (the regular wood or paper-type fires) because they may not be able to displace enough oxygen to put the fire out, causing it to re-ignite.
During my CERT training they let us do a quick blast out of one, and at 20 feet away it was like an ice storm.
Just to amplify, CO2 extinguishers work by depriving the fire of oxygen. The reason they are not so good on wood is that they have only a limited cooling effect (the heat capacity of the gas is much less than water) and this is what allows the fire to reignite. They are also not very effective out of doors as the CO2 gets blown away allowing oxygen back in.
Not for use on paper as the blast of high pressure gas will scatter flaming pieces of paper all round the room. Spectacular but not too good for fire fighting:smack:
Close up the CO2 stream will freeze anything in its way and the nozzle will rapidly freeze your hand to it if you don’t read the instructions and hold the extinguisher wrong!
The fire triangle is heat, fuel, oxygen though - although CO2 extinguishers primarily deprive a fire of oxygen, the low temperature of the gas probably has some kind of secondary effect, especially on fires where the fuel is emitting copious flammable vapours (such as oil-soaked wood, maybe)
If a fire is at or very near the combustion temperature then the temp drop could aid in putting the fire out. The mass of the CO2 being used in comparison to the amount of energy that would have to be adsorbed means a very little temperature drop of a fire.
The movie bit where the door is frozen it just a movie. It would take a large extinguisher really large.
The white stuff that commes out of a horn of a CO2 extinguisher is a mixture of Dry Ice and Ice. That is why in classes it is taught to be careful on using it on a electrical fire, Never touch the horn always use the wooden handle.
So there are extinguishers that, through process of expanding gas, can lower the temperature of something it’s pointed at.
But it’s unlikely to be enough to freeze a padlock to the point where you can shatter the padlock with a casual swipe of the extinguisher, right?
And it’s unlikely to be enough to freeze a door so you can kick your way through it.
And if you are using the extinguisher to cool down little critters (a’la first season Sanctuary), the CO2 might affect them more than the lowered temperature of the extinguisher blast?
Or is it cold enough to put little critters into hibernation, shatter padlocks, and weaken doors?
Assuming the padlock’s made of something like metal, for instance? Not a chance.
Assuming, again, that the door’s made from the usual sort of door-making materials, that’s right.
Difficult to say for sure – are these real-life critters, or made-up TV fantasy critters?
If I ever find myself in a situation where my life depends on the answer to any of these questions, I’m going to assume the answer “No” and move on to Plan “B”.
On the other hand, Mythbusters has conclusively proven that a CO2 extinguisher will chill a six-pack of beer to frosty drinking temperature in under 30 seconds. So at least that’s something, yeah?
CO2 extinguishers are not so cold due to the expansion of gas. They are that cold because they contain mostly liquid CO2 rather than gas, so it is the latent heat of vaporization that the CO2 sucks from the air, rather than the much smaller temperature change associated with adiabatic expansion.
Nother Nit: Baking soda based extinguishers are better for some types of fires because they leave a fire retardant powder coating that keeps hot stuff from re-igniting. In contrast, the CO2 will quickly leave the scene allowing the fire to re-ignite due to stored heat or flame from another part of the fire. I once extinguished a burning motorcycle with a CO2 bottle, and it took several tries to get the two major parts of the fire out at the same time.
It is worth noting soda extinguishers typically contain nitrogen at much higher pressure than CO2 extinguishers, yet do not produce near the cooling.
There is a hollywood meme at play here that goes something like: “anything frozen will shatter into a thousand glittering shards”.
This might be true for some objects, and maybe more objects at very, very low temperatures, but just freezing something doesn’t automatically make it brittle enough that it will shatter. Drop a frozen leg of lamb on a concrete floor and it may chip the concrete.
In an episode of “Bones,” they thought that a frozen body part would explode into a million pieces. They threw or fired it it at a table and it bounced around breaking stuff in the lab.
Regarding the other posts, thanks for helping to clear all that up.
I took Fire Safety including learning how to put out a fire with an extinguisher. The trainer explained that extinguisher fires a powdery salt-like substance which puts a barrier between the fire and the oxygen. He explained how to spray it around the base of the fire to make sure we coat the entire area with the powder, and had each person in the class try it until they got it right.
At no point during that training did we cool anything down with the extinguishers.
Probably won’t freeze them but depending on the creature, the size of the CO2 extinguisher, the size of the room you’re in, etc. you might be able to suffocate them.
nitpick on nit pick.
I think you are taking about dry chemical extinguishers.
the only extinguishers with Baking Soda that I have seen were outlawed in most states aroung 1982. They were not really outlawed, it was just against the law to do a hydrostatic teat on them.
No, the tasty lamb dinner is what you feed the police detectives, as they are looking around the house & neighborhood trying to find the heavy, blunt object that was used to kill your husband.