Exit bag gas CO Helium N2

[orca87]

As far as I understand, helium is the preferred method for the exit bag because it is lighter than air, and thus a constant flow of He pushes the CO2 that you exhale out of the bag.

Nitrogen (N) on the other hand seems more suitable for SCBA method as it has roughly the same weight as air and hence works with demand valves.

CO (carbon monoxide) is a gas that is oder less and shouldn't cause respiratory irritations, just like the other gasses. It should, however, be more "toxic". At least it is my understanding that CO causes a quicker death and renders you unconscious after just one Inhale.

CO however, is hard to get as a pure gas in a cylinder. Highly regulated chemical.

I might have found a source of 5% CO in N2. How does N2 differ from N in terms of its effect for our purpose and would the 5% CO have any benefit?

Thanks

 

[ThisIsLife]

Between He, N2 and Ar, He is the lighter in density and Ar the heavier.

You're right about the fact that He being lighter than air, it can "push" exhaled CO2 out of the bag more easily, since it fills the space logically from the top to the bottom, but N2 is not dramatically heavier, at least not enough to make such a difference of pushing CO2 out of the bag less rapidly, but adjusting the flow can help. Ar, on the other hand, is so dense that i can't recommend using it with EB, only with SCBA setup.

The main difference with these gases and CO is that He, N2 and Ar can't trigger any automatic survival response since your body will only monitor CO levels. They will replace O2 and your body won't notice.

How does N2 differ from N in terms of its effect for our purpose and would the 5% CO have any benefit?

N2 doesn't differ very much from N in its effect since your whole nervous system shuts down rapidly in both cases, so you won't be able to notice anything, you'd blackout in seconds and the body won't be able to respond to the threat in any way.

CO doesn't have any benefit at all.

Don't overcomplicate things: the purest He or N2 you can get (grade over 2.8) will do the job perfectly.

 

[GasMonkey]

Nitrogen (N) on the other hand seems more suitable for SCBA method as it has roughly the same weight as air and hence works with demand valves.

N₂ is perfectly suitable for the ExitBag, in fact the optimal flow rate was determined using Air which as you have said has roughly the same weight as N₂ (28.96 g/mol vs 28.0134 g/mol).
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5% CO have any benefit?

No, totally the opposite. With inert gas you can abort if you want with no consequences (O₂ saturation will be restored and that's it) which isn't the case with CO (if you abort the CO will still be inside you and it will fuck you up).​