SCBA and "the bends"

[newdiverAZ]

O.K. this may not be the place to post this question, if it is not please move and my apologies, but it kinda pertains to the same theory as scuba.
If a fireman breathing from an scba on land for 2 hours was to board a commercial flight, would he be at risk of dcs? I would think the nitrogen loading would be minimal but still possible. Am I way of base in this assumption?


Brian

 

[scuberd]

as far as I understand deco theory, the person has to be breathing under pressure. A fireman is taking on the same nitrogen load as he would breathing without scba and therefore no more at risk than any other passenger on the plane

 

[newdiverAZ]

but you are at a greater pressure than you would be at on an airliner? Was curious is all my brother in-law is a fireman here and we were talkin bout this stuff.



Brian

 

[Waterborne]

Scuberd is correct in his reply. Breathing from an SCBA on land is the same as breathing without it. You and the SCBA are under no more pressure than the average Joe therefore, not taking on any additional nitrogen load. As far as being under greater pressure on land than on the plane, airplanes cabins are pressurized. The air gets thinner with altitude which makes for a harder time exchanging gases. That is why airplane cabins are pressurized. Hence the reason that if cabin pressure is lost, masks drop down from the ceiling with O2 for passengers to breathe.

 

[DiverBuoy]

The compressed gas is being delivered to the recipient at ambient pressure (1 atmosphere) - when the user is just walking around on the ground at sea level. This is the same pressure you and I get from taking a normal breath without the aid of a self-contained breathing apparatus. There is no danger therefore doing this, any more than you or I experience when we fly at anytime. We're breathing at this pressure everyday.

At depth a greater amount of gas is delivered with each breath. Inert gases like nitrogen, argon and helium are not consumed by our bodies like oxygen. So these gases under pressure are being "packed" into our bodies tissues. When the pressure decreases these gases want to come back out of our tissues. If we decompress too quickly that is when it becomes dangerous. Instead of slowly coming out of the tissues, rapid decompression causes damage to the tissues, blocks blood flow, and bursts things that can't take the pressure that quickly.

The magic of all this happens in the regulator, it decides how much gas to let us have - by essentially "measuring" the pressure around us. If it failed to deliver enough gas at depth it would be so difficult to inhale - our lungs would not be strong enough to force back all that water pressing in on us so as to get a full breath. This simply isn't required for breathing at 1 atmosphere of pressure or at sea level, so these gases aren't being "packed" into our tissues so as to prevent us from flying.

moved thread with redirector to Dr. Decompression forum

 

[Dr Deco]

Dear Readers:

Self Contained Breathing Apparatus

As long as the firefighter is not breathing pressurized air, the risk is the same as an ordinary “earthling.” This is what the other respondents answered.

There is only a problem if the external pressure was increased, and the firefighter took on an increased load of nitrogen. It is not clear to me how that could be possible with SCBA gear. It might make a good story, and possibly Michael Creighton could find some masterful way for an exciting mystery novel. :wacko:

Dr Deco :doctor: