SCBA's

[backdraft663]

No its not a post about which ones better.


I have heard many different things about SCBA's, bhat is actually in them. What kind of air?

[ChiefDog]

In 99.9% of the ones I know about it is the same air you are breathing in your station. (Or place you get them filled.)

You only compress the air, run it through filters/dryer and then into the cascade. From the cascade the bottles are filled to your needs 2216/3000/4500psi.

Rebreathers, (very limited use in Fire Service to my knowledge.) may give a shot of O2 in to the air to keep the O2 level up.

[SamsonFCDES]

There can also be things like carbon monoxide and polutants from apparatus exhaust unless you have your compressor set up properly to draw air from the cleanest place possible.

NASA developed a liquid air SCBA that last for a very long time but is open circute. It has just plain old air compressed and then chilled to be liquid, sort of like a propane tank.

Rebreathers recylce the air from your lungs, have small oxygen bottles to add O2 into the mix, and CO2 scrubbers to clean out C02.

Drager makes one that is still used for fire fighting in situation that require long duration use, IE 4 hours and such.

But when it all comes down to it you are just breathing regular air.

For SCUBA there are special mixes, IE NITROX and such that are designed to lessing the ill effects of diving deep and such. Some are helium and oxygen IIRC.

[HM604OH]

OSHA has minimum requirements for breathing air used in SCBAs:

1910.134(i)(1)(ii)
Compressed breathing air shall meet at least the requirements for Grade D breathing air described in ANSI/Compressed Gas Association Commodity Specification for Air, G-7.1-1989, to include:

Oxygen content of 19.5-23.5%;
Hydrocarbon (condensed) content of 5 milligrams per cubic meter of air or less;
Carbon monoxide (CO) content of 10 ppm or less;
Carbon dioxide content of 1,000 ppm or less; and
Lack of noticeable odor.

You should have your air supply tested on a regular basis.

I once had a situation where several firefighters became ill during a training session in a non IDLH atmosphere. We used some detector tubes to test the air and discovered that it contained contaminants. The dept. sent a sample out for a regular test and the results confirmed what we suspected. The compressor was repaired and additional tests were conducted to determine that the problem was resolved.

We had another case where a dept filled their tanks from a cascade system that used bottles from a local industrial gas supplier. Once again, we had firefighters report being light headed during an exercise. We tested the air with our O2 meter and discovered that the level of oxygen in the air was low.

Don't assume your air is Grade D unless it has been tested.

[Rescue101]

Ours is grade E and tested annually by an independant lab. T.C.

[Bones42]

Ditto to Rescue101 except our testing is quarterly. I believe Grade E is required for SCUBA tanks.