What are reasonable limiting PO2s for decompression diving?
By what amount do tech divers generally pad their expected gas requirements?
Can dive planning software be used to calculate the volume of gas needed for any given segment of a dive?
How do you use the NASE Gas Management Spreadsheet?
Key Points to Remember
Given the intensity and duration of exposures to high concentrations of oxygen, many tech divers — and, especially, those using rebreathers — will limit oxygen exposure during the active or “working” phase of the dive to 1.3 ATA. During your shallowest decompression stops, a limiting PO2 of 1.6 ATA is widely considered acceptable.
To allow for contingencies, it’s a common practice to “pad” the gas volume theoretically required for any dive segment by an additional 50 percent.
Some dive planning programs may include a function for calculating the volume of gas needed for any given segment of a dive, based on SAC rate and the resulting RMV.
To use the NASE Gas Management Spreadsheet, you need to know your “working” SAC rate and, if possible, your resting SAC rate as well. Other than that, entering the depths and times of your various dive segments is fairly intuitive.
