Back in college I had a part-time job delivering prescirptions and surgical supplies. At a few places there were patient who required oxygen and would drag around their tanks. There would be stickers and signs pasted everywhere warning “Danger: Oxygen - No smoking.” “NO OPEN FLAME!” “Danger! Risk of explosion.” etc.
So I was wondering… Firefighters carry tanks of oxygen on their backs and run into burning buildings. Is there a danger of an explosion from their tanks? Is the air formulated a little differently (as opposed to the pure O[sub]2[/sub] of the hospital patients). Are the masks super air-tight? Do they just weigh the risk differently?
Fire fighters’ airmasks are certainly not airtight - where do you think the air goes to?
And the air is indeed “formaulated” a bit differently to pure Oxygen - it’s air!
The possibility of an explosion is considered a reasonable trade-off with the guarantee of no smoke-free, room-temperature air to breathe. I’m guessing they have more heat-resistant tubing and such on their rigs.
They don’t carry pure oxygen on their backs. (IIRC breathing pure Oxygen for long periods will destroy your lungs)
Instead they carry a mixture which has no more oxygen than what you would normally breathe.
If you go to a firehouse, they will gladly show you the unit which mixes the tanks for them. ( I used to know the name, but it has been years since I did the firefighting thing)
Sooo…To answer your question: No, they will not go ‘boom’ in a house. Not any more than the air which is already inside.
The air exits the mask through one-way valves. I have in fact examined one that was constructed the same way as a gas mask. I was wondering about leakage.
Which is why I’m asking.
I would have thought there would be some benefit to a slightly more oxygen-rich formula considering the physical demands of the firefighters in such adverse conditions.
So the tank then does not contain more oxygen rich air – just your standard air compressor pumping air from whatever environment? Great.
Thanks, Spit. Your post was most helpful. I was aware that pure oxygen is for compromised lungs (ie/ pulmonary fibrosis) but I thought firefighter tanks were perhaps mixed differently and I had also assumed that pressurized air might be more volatile.
I’ll have the mods close this thread and I’ll contact the stations down the street.
A little confusion here. You are talking about an air purifier here, not an SCBA (self contained breathing apparatus). These are basically gas masks. They do not have an air supply, and are designed not to leaks around the seals. The SCBAs that firefighters use are positive pressure systems that supply air from a bottle. The masks are designed to leak - outwards, keeping all the toxic fumes away from the guy inside.
It is not oxygen but air (although the dew point is controlled for the air). Read here about the construction of a firefighter’s Self-Contained Breathing Apparatus (SCBA).
There is also a pressure valve at the bottom of each of the tanks. If the temperature rises too extreme, the valve will simply blow out. This would prevent an explosion of another sort…not one from the mask itself, but from the increased pressure from within the air tank.
My father has been in the NYFD for close to 30 years now, and says that he has never had his tank blow this valve. Not sure as to what temperature would have to be reached for this to happen.
Just to confirm what everyone else has been saying, firefighting SCBAs simply contain compressed air. It’s really no different from a SCUBA tank. We fill ours off a cascasde system at our fire hall. We also have a compressor so we can fill our cascade tanks, and we can also use it to top off or fill SCBA tanks.
Tapioca is about half right. It is a positive-pressure system. However, exhaled air is released through a one-way valve. The mask shouldn’t be leaking anywhere else. In fact, OSHA requirements include a fit-test of masks for all firefighters. The fit test checks the seal of the mask without any airflow from the tank.
Cool, thanks. That was the other aspect I was wondering about. I had assumed that for temperatures to be high enough for the pressurized tank to blow, the firefighter was sure to be in such deep trouble that an exploding tank would be the least of his/her worries, but I was still wondering.
That’s what I saw – it looked pretty leak-proof and kind of wrapped around one’s head with a one-way valve (the one I saw was damaged so the valve buzzed a little.)
One more question about the masks: Do they fog up/how do you control fogging?
Yes, they do. Especially in Minnesota in the winter. However, once you start breathing air from the tank, the mask usually defogs itself. (This is an issue because usually we’re suited up with a mask on, but without air, while waiting for orders to enter, or while on a Rapid Intervention Team). Aside from that, keeping the inside clean usually helps, too.
If your SCBA air cylinder is compromised, in any way, you will get f**ked up. And it does happen on occasion, although I don’t know of it personally happenning on anyone’s back. In a structural fire, which at some point becomes “oxygen controlled”, the rupturing of an air cylinder will be problems for the wearer for certain; if the bottle were filled with oxygen, and it ruptured, your crew would be hurting as well. Cylinders are pressurized to several thousand PSI; even if you blew a valve, the cylinder could “rocket.”
Face masks DO NOT leak, but you must be concerned with cutting the air hose or damaging the regulator.
Face masks do fog up, especially if you don’t have a nosepiece, but who cares, you can’t see jack anyway in a structure.
Some firefighters DO use pure oxygen tanks - rebreathers, for instance, the HazTechs in their suits use them. You may need a pure oxygen rebreather for an extended period of time in a toxic atmosphere, as most air SCBA are only good for about 20 minutes. However, no one is too keen on wearing one of those bombs into a fire.
Portable O2 bottles (for folks with breathing problems) can be a problem. A normal Buick Park Avenue fire with an O2 bottle inside will increase your pucker factor by about 10 when it blows.
I am a fire fighter and have used SCBA on countless occasions. The mask does fit air tight but it has 2 1-way valves. One for inhale and one for exhale. The air dont always run only when you inhale do you git air. it is made like that so you dont just run out of air in a show time. And as far as exploding we naver actually fill the tank to the max we usually leave 10 mins of air out to account for the expansion. The mixture is this, normal air with the moisture taken out. Some new tanks are actually fiberglass and very lightweight.