Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
Ability to post and comment on topics and discussions.
A Free photo gallery to share your dive photos with the world.
I have paid attention to my gear with regards to this issue; with my analog gauge reading ~250 psi, fully inflating my Large SeaQuest vest BC takes just less than 100 psi (80 cft).
I always orally inflate before the dive, unless it is a negative entry.
How many breaths is that? I'm guessing you're taking it to the extreme and blowing it up completely and that it has a large volume bladder anyway. Cos inflating my BC on the surface does not use up 3.3% of my gas for the dive.
If I'm wrong on this general point - and god knows I have been before - I'll reconsider orally inflating before diving.
To whip a dead donkey a little more - not only do I not care about power inflating my BC, I generally breath from my regs for a few minutes before jumping in. This allows me to be sure gas is on and check for any other sundry gas delivery issues there might be. The gas I use for both activities is negligible from observing my gauges (but I haven't made any exact record)
I am never first to finish a dive.
I have never gone OOG.
My dives (typically going 30m+) are usually longer than an hour.
I often dive in strong current.
I smoke
I drink
I'm overweight (a little)
My simple point being - orally inflating your BC is not going to make any difference to your bottom time and absolutely negligible difference to any safety margin. At least with my BC anyhow which is a bog standard Mares dragon poodle jacket.
To whip a dead donkey a little more - not only do I not care about power inflating my BC, I generally breath from my regs for a few minutes before jumping in. This allows me to be sure gas is on and check for any other sundry gas delivery issues there might be. The gas I use for both activities is negligible from observing my gauges (but I haven't made any exact record)
I am never first to finish a dive.
I have never gone OOG.
My dives (typically going 30m+) are usually longer than an hour.
I often dive in strong current.
I smoke
I drink
I'm overweight (a little)
My simple point being - orally inflating your BC is not going to make any difference to your bottom time and absolutely negligible difference to any safety margin. At least with my BC anyhow which is a bog standard Mares dragon poodle jacket.
I have paid attention to my gear with regards to this issue; with my analog gauge reading ~250 psi, fully inflating my Large SeaQuest vest BC takes just less than 100 psi (80 cft).
I always orally inflate before the dive, unless it is a negative entry.
Sounds like the accuracy of my gauge from 250 psi to 160 psi is being questioned! If you just lay on the button until the relief valve burps do you think 90 psi from 3000-2910 is more air than from 250-160?
Lamont is correct, SPGs are notoriously inaccurate and nonlinear down towards the end of the scale. The only thing that the manufacturers try to assure is that when the SPG goes to zero there is still a little air left in the tank.
The second question was the one less tongue in cheek. You did check out 160 psi on that gauge didn't you? So, with a digital gauge, would 100 psi from the tank be the same cubic feet off the top of a full tank compared to 250-150?
My simple point being - orally inflating your BC is not going to make any difference to your bottom time and absolutely negligible difference to any safety margin.
You see, there's your problem. When you finally exhaust your tank trying to get the last bug out from under the rock, then you are thinking you wish you had just a little bit more.
I have no research or data to support this but my dive instructor stated during training one time that oral inflation during the dive actually wastes more air than manual inflation because of the way it changes your breathing patterns when you do it. So you save some air in your tank by orally inflating but then make up for it by breathing harder after you do so.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
- I'll reconsider orally inflating before diving. 
