sea_otter
Contributor
I've been looking at dive planners for a couple 30/30 dives, comparing GUE's minimum deco tables and multideco, and I was quite surprised to see a significant discrepancy between the two.
For example, if I'm planning a dive to 100 ft on 30/30 for 25 minutes (per GUE, within min deco limits with some margin), a planner set to 20/85 gives me a mandatory 7 minute stop at 20'. If I push this to the GUE min deco limit of 30 minutes, I see a mandatory 11 minute stop at 20' (this assumes staying on back gas to the surface - not plan A in our case - but an option).
I questioned my instructor on what I thought was a slight variance (though after punching the numbers, I'd call that more than a slight difference), and his response was that the constants for Bühlmann's constants related to helium were never really tested when the algorithm was developed, and that as a gas, it behaves more like nitrogen. I'm curious to learn more about this - is it really valid to have tables that show the same min-deco limits for 32% as 30/30?
For example, if I'm planning a dive to 100 ft on 30/30 for 25 minutes (per GUE, within min deco limits with some margin), a planner set to 20/85 gives me a mandatory 7 minute stop at 20'. If I push this to the GUE min deco limit of 30 minutes, I see a mandatory 11 minute stop at 20' (this assumes staying on back gas to the surface - not plan A in our case - but an option).
I questioned my instructor on what I thought was a slight variance (though after punching the numbers, I'd call that more than a slight difference), and his response was that the constants for Bühlmann's constants related to helium were never really tested when the algorithm was developed, and that as a gas, it behaves more like nitrogen. I'm curious to learn more about this - is it really valid to have tables that show the same min-deco limits for 32% as 30/30?