Gas Math - Help

[AbyssalPlains]

Thirds are calculated AFTER you subtract your rock bottom, it's not a replacement. The way I understood it, if your rock bottom for two stressed divers at 100ft is, say, 1000psi, then your thirds calculation is reduced to 1640psi usable gas, so you have roughly 550psi in, 550psi out, 550 in reserve, and 1000psi for RB.

Interesting. I have never seen or heard it being done this way. In all the classes I have taken so far, including SDI solo diver and TDI Deco, the rule of thirds does not factor in a rock bottom. The way I understand it it is an alternative way of doing things. You either follow rock bottom or you follow rule of thirds.

 

[Gombessa]

Interesting. I have never seen or heard it being done this way. In all the classes I have taken so far, including SDI solo diver and TDI Deco, the rule of thirds does not factor in a rock bottom. The way I understand it it is an alternative way of doing things. You either follow rock bottom or you follow rule of thirds.

The posts immediately following that one include discussions on different ways of using thirds, and outlining some scenarios where thirds alone may be inadequate.

 

[raider11]

Thanks everybody for taking the time to comment on this threat.

I don´t plan to make dives that required deco stops for a long time, I will be diving rec only and within NDL. But I didn´t have my table at hand when I wrote and didn´t realize that more than 20´at 100f is a deco dive.

I was just thinking about different rec dives like TSand explained.

I´ll keep reading, learning and diving as much as possible. Thanks again to everyone.