Gradient factors and the depth at which the first deco stop is planned

ken chung ar

hi connoisseurs in tech diving,

i have been learning gradient factors used in the decompression planning in deep diving and read "clearing up the confusion about deep stops" and "understanding M-values", both of which were written by EC Baker.

it is my understanding that, in order to reduce the inert gas pressure gradient, a gradient factor (GF) is introduced. it is a percentage of the M-value gradient, i.e. a division of the inert gas pressure gradient by M-value gradient.

now, GF-Low determines the depth at which the first deco stop is planned. the lower the GF-Low setting is, the deeper the first stop needs to be. this is consistent with my understanding.

however, when i saw Figures 1 and 3 in "clearing up the confusion about deep stops", the relationship between GF-Low and the first deco stop depth seemed reversed! the conservatism factor was minimal (15%), and the deco started at -33m in Figure 1; whereas GF-Low was 20%, and the deco started at -54m in Figure 3.

i am more confused and cannot explain this apparent contradiction. at least, this paper does not clear up my confusion, and so i need your help it.

thank you in advance.

ken chung ar

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hoppyinca

Look at the article again...
Figure 1: profile generated with the conventional Calc method (the conservatism factor IS NOT a GF).
Figure 2: profile generated using the empirical method developed and published by Richard Pyle (again conservatism factor IS NOT a GF).
Figure 3: profile generated using GFs...

basically it is a progression from the most aggressive profile to the most conservative. With only the last and most conservative actually using GFs.

BTW, I am not an expert; this is merely my interpetation/ understanding...

Hope that helps.
Hoppyinca