Why not 30%?

[stairman]

Of course 32% is the most common but it seems 30% should be for the many systems in the 100 ft range, keeping the 02pp below the 1.4 or 1.5 range.

[Kelly Jessop]

Of course 32% is the most common but it seems 30% should be for the many systems in the 100 ft range, keeping the 02pp below the 1.4 or 1.5 range.

I agree,and prefer a lower mix for deeper,high flow systems. I know at one time 34% used to be banked,which always made me nervous,and I would thin it out with air. What is real scarry,when nitrox was first really introduced we used to dive Ginnie with 36% to 38%,and Ginnie used to really pump then-surprised in retrospect that we didn't have more cases of oxtox.

[Marc Bryan]

I dive 30%. I think it is the best choice for a number of reasons.

In high flow systems like Ginnie and JB where the depth can reach 90-100ft, I think it is crucial to keep the PO's low. The extra exertion just tips the scale IMO.

When you look at studies the incidence of tox at 1.4 is very low, but at 1.2 it is significantly lower (on my iPhone so don't have the numbers, but is way lower on the curve).

The extra minute or two of deco is insignificant to me.

Here in cave country almost everyone (except Jim Wyatt, he pumps 30%) pumps 32%. I always squirt some air in before filling to bring the % down.

[amphipod06]

Well, I keep my setpoint to 1.0 for most dives and only up it on deco, does that count?

Dive safe,

Celia

[aainslie]

i agree, 32% is definitely aggressive for a lot of the "standard" Florida caves. And for the shallower ones, it matters less anyway since the deco is less. Dropping to 30% would be really nice.

[Marc Bryan]

I have made a point to mention the studies and present a case to a couple of the local shops.

The response I get is, "Well everybody likes 32%, that is what they are used to.".......

Some people have actually claimed that "All of the standard Nitrox tables are for 32%"

Or my favorite, "I like the extra O2 to lower my chances of getting bent." To which I always reply, "Yeah, I would much rather tox than get bent....."

[Marc Bryan]

Well, I keep my setpoint to 1.0 for most dives and only up it on deco, does that count?

Dive safe,

Celia

Since females seem to be more susceptible to O2 hits, I always have my wife dive a 1.0 or lower on a high current, high work type of dive.

[Sludge]

Some people have actually claimed that "All of the standard Nitrox tables are for 32%"

I work at an open water shop that still teaches there are two nitrox mixes, 32% and 36%.

[Marc Bryan]

I work at an open water shop that still teaches there are two nitrox mixes, 32% and 36%.

Good Ol' NOAA I & II

[ScubaBob-Squaretank]

If I dive with several stages at Devils I mix it to 29 %. It sseemed that 30 was still pushing the O2 still higher than I prefered.
Bob Klauck