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You're choosing your gradient factors wrong...

Sun, September 20, 2020 12:26 PM Comment(s) By Team DSS

Choosing your gradient factors (GFs) is a contentious subject for new and experienced technical divers. . If you do, and you’re not confident in the numbers on the computer, then, welcome to the club! I want to break down some common misconceptions about what constitutes a good idea when choosing gradient factors.


If you don’t have a good grasp on what a gradient factor is check out this resource:

Learn about GFs

“Someone else does it [and isn’t getting bent]”

“Not getting bent” isn’t a great metric for choosing a gradient factor. In fact, it's a horrible metric as it can easily lead to serious normalization of deviance. Another person not getting bent is an even worse metric. How many successful dives (no DCS) were made on Haldane, Workman or Buhlmann tables? Lots! How many “extreme” dives have been conducted with no ill effects on “aggressive” profiles (higher gradient factors)?  Conversely, there have been plenty of “normal” dives done on “conservative” profiles (lower gradient factors)*. There’s more at play than just a choice of gradient factors

“I feel better after the dive now that I use XX/YY”

There is obviously a range in which this phrase is valid. If a diver is extremely fatigued after every dive and they do more decompression and they are no longer fatigued, that sounds like the right move. But, this statement in general is attributing a change in arbitrary feeling to gradient factors, when that probably isn’t the major contributor. In my experience this is typically the result of someone deciding to change their GFs and then, because they just changed something, begin to pay more attention to how they feel after a dive. Other variables, like predive fatigue, hydration, thermal stress and diet probably play a much bigger factor here. The other problem with this line of thinking is that we’re using our bodies as test dummies. While decompression isn’t an exact science, the idea that you can use a nonspecific highly variable factor as a test parameter is pretty silly.

“As you dive more you figure out the correct gradient factors”

See above. Unless you’re getting bent after diving (and considering the amount of different stressors, even then really) this idea of dialing GFs as dive experience increases doesn’t make any sense. As dive knowledge increases is completely reasonable, but not as dive ability increases.

The discussion on GFs always leaves a key component out. Decompression algorithms are not the holy grail of mitigating risk. They are a piece of the puzzle, and not necessarily the largest piece.


Is selecting a GF important? YES. 

Is understanding the logic behind GFs and decompression models important? YES.


But the other stressors are too often ignored. Fitness, fatigue, hydration, thermal stress and exercise are components that are a consideration for every single technical dive. Having hours of discussion on GFs and no consideration for the other factors is seeing a tree, but not the forest. It’s just as big of a blunder as high technical skill proficiency without any non-technical (human factors) proficiency. Further, picking any two (i.e. GFs and hydration) is missing the point.

Decompression Stressors

How should you choose a gradient factor?

Here is the ultimate question. The short answer is: Eh, there’s nothing set in stone.**

The long answer is: You need to be educated on what a GF is, what it’s based on, and the research that backs up low VS high methodology without ignoring the other factors.  It’s every technical diver’s responsibility to understand these factors and mitigate them to the best of their abilities. 

*Aggressive and conservative profiles are in quotations as a lower gradient factor isn't necessarily a more conservative profile.
** While nothing is set in stone, there are important recommendations to mitigate risk. This sentence is not designed to imply that GF selection doesn't matter.

Team DSS

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