Question Solved - Peregrine MOD 59m for air??

[batdiver_82]

Hi!
My Peregrine shows a MOD of 59m for air (PPO2 1.40). My calculations would be 57m 1.4/0.21=66.66 ata - 0.966 shown surface pressure). How comes that the Peregrine calculates 59m?

 

[inquis]

I suspect it is set to fresh water.

 

[tursiops]

Are you assuming salt water but the Peregrine is assuming fresh water?

 

[batdiver_82]

Thanks a lot... "Problem" solved - both of u are completely right!! The problem was the user!

 

[justinthedeeps]

So the question is answered, but anyone care to debate what we should today consider the "maximum operating depth" for a gas?

1. ppO2 < 1.4 (or 1.6 for a 'deco gas')
2. narcotic effect < ~40m EAD/END MAX? (but ideally more like 20-30m, aka ppN2 < ~3atm)
3. gas density < 7 g/L at depth
4. ...?

Modern definitions beyond just ppO2 put the maximum operating depth (=MOD) of air more around ~40 metres

People still do occasionally go to 60 metres on air (I have, as an experiment) but it is not recommended.
That applies whether it is a primary breathing gas, a bailout, or a diluent, for the same reasons (narcosis & density)

An accident happens at 70 metres on air... Was ppO2 the cause? Maybe... Or was it a super narc'ed out, CO2 loaded diver running low on gas making bad decisions?