UWSojourner
Contributor
There is a calculation in the back of Deco for Divers for NDL but for a specific ascent time it gives you the partial pressure at which you must start ascending. There isn't anything in that equation that represents time spent at the current depth.
There is a formula in Baker's "Calculating the no-stop time" but it can only be used where Pi > Mo > Po (on-gassing) or Pi < Mo < Po (off-gassing). Pi is the inspired inert gas pressure, Mo is the surfacing m-value, and Po is the previous inert gas pressure of the particular tissue compartment being computed. I tried using it in an earlier version of the spreadsheet but I had to ditch it because there were some dive segments that didn't meet the conditions of the formula.
You can still use Baker's formula I think if you just look for conditions where you're already in deco (i.e. NDL=0) or where you can never reach deco (i.e NDL=999). For example,