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OSTC2 (v. 2015) with hwOS 3.18 firmware

Hi,
The gas density warning threshold seems identical in OC and CC configuration. Is it normal?
(there is normally more tolerance in open circuit)
Rgds,
Michel

Hi Michel,

you are right, the thresholds are independent of the operating mode. They can be changed, but only with external software (but probably that's not supported yet in subsurface / libdivecomputer etc.). Do you have a source on why OC should be more tolerable than CC? I can't really make my mind if cold & dry vs. warm & humid makes a significant difference (and in what direction) to the gas flow turbulences in the airways that gas density warning is all about.

BR
Ralph

Hi Ralph,

I've read this on shearwater petrel 2 release notes:
(I'm really sorry, I have a shearwater too )

For Closed Circuit Diving: The gas density display turns yellow at 5.2 g/L and red at 6.3 g/L. No other warnings are generated.
For Open Circuit Diving: The gas density display turns yellow at 6.3 g/L. No other warnings are generated.
You may be surprised at how shallow these warning colors appear. Read more about why we chose these levels starting on page 66 here (recommendations on page 73):
https://www.omao.noaa.gov/sites/default ... 202016.pdf

Maybe there are answers in this article.

Rgds, Michel K

Hi Michael,

thanks for the post and the link to the article!

The OSTC also defaults to 5.2 & 6.3 g/l as attention (yellow) & warning (red) threshold.

What i was wrong with in my earlier post is that the OSTC only tracks the gas density in CC mode, not in OC. This decision was based on the fact that in OC gas mix planning for the target depth is done before the dive and so gas density considerations for the mix can be figured in "offline". But in CC gas mixture is constantly changing, with density going up on O2 injection, so an "online" checking becomes beneficial.

best regards,
Ralph