Air Consumption Curiosity

[EFX]

To reduce gas consumption: Get your weight right (no more than +2 lbs[1 kg] heavy).

A warning to new divers:

My weight is down to within 2 lbs and while remaining still (no finning) at the surface I have to exhale completely to descend. I hold my breath until I get about 8 ft down then take a small inhale. When I'm below 15 ft I take a deeper breath and breath normally after that. Oh, I'm wearing a 7 mm full, hood, gloves, and diving with an AL80. I'm also talking about a vertical head-up descent. I know ... it breaks the cardinal rule of "breath all the time" but I have a brain and the danger is on ascent not descent. If this scares the hell out of you then add weight (probably just 2 more lbs) until you can descend slowly on a normal breath.

 

[boulderjohn]

A warning to new divers:

My weight is down to within 2 lbs and while remaining still (no finning) at the surface I have to exhale completely to descend. I hold my breath until I get about 8 ft down then take a small inhale. When I'm below 15 ft I take a deeper breath and breath normally after that. Oh, I'm wearing a 7 mm full, hood, gloves, and diving with an AL80. I'm also talking about a vertical head-up descent. I know ... it breaks the cardinal rule of "breath all the time" but I have a brain and the danger is on ascent not descent. If this scares the hell out of you then add weight (probably just 2 more lbs) until you can descend slowly on a normal breath.

It is especially important to get weight right when wearing as much as a 7mm suit, hood, and gloves. Even if you do as EFX describes, you will be overweighted once you reach depth. You have no choice. Your wet suit, hood, and gloves will compress significantly, so that the amount of weight you needed to begin the descent will not be needed once you are deeper. Unfortunately, you can't hand those weights off to a "weighter" during the dive and then retrieve them for the ascent.

 

[EFX]

It is especially important to get weight right when wearing as much as a 7mm suit, hood, and gloves. Even if you do as EFX describes, you will be overweighted once you reach depth. You have no choice. Your wet suit, hood, and gloves will compress significantly, so that the amount of weight you needed to begin the descent will not be needed once you are deeper. Unfortunately, you can't hand those weights off to a "weighter" during the dive and then retrieve them for the ascent.

Yes, very good point. According to DIR: the fundamentals of diving, a 7mm full wetsuit loses 9 lbs of buoyancy at 100 ft. Most novice divers are probably at least 10 lbs overweight. The BC has to compensate for about 9(60/100) + 10 or about 16 lbs at 60 feet assuming a constant rate of compression. That's huge. Having excess weight can also create big swings in buoyancy not to mention bad trim, and buoyancy issues are a main contributor to diving fatalities.