Testing oral inflate as part of kit setup or buddy check ...

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roydude

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Scuba Instructor
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147
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Location
Scotland
# of dives
1000 - 2499
Howdy all!

During kit setup checks or buddy checks I've come across a few divers who, as well as testing that the LPH assembly will correctly dump air, also test that they can orally inflate with it.

I don't really want to question it because it doesn't cause any issues and takes a few seconds but this seems to me like a lack of understanding about how the LPI 'dump' assembly works. Pressing the deflate button on that assembly basically just creates a hole in the bladder (so air can escape or be pushed in). If you test it dumps, you've tested that air can move through the hole.

Surely if air can pass through a hole it in one direction, it can also pass through it in the other direction?

What value does checking oral inflation add if you know the assembly dumps correctly? Is there a situation that the hole may work in one direction (dumping air from the bladder) but not in the other direction (orally inflating)?

It sounds silly, but it's a genuine question: if there's a good reason for this test I'm totally going to include it in my OW classes. I don't want to add something unnecessary but also I wanted to check I'm not missing something important.
 
What value does checking oral inflation add if you know the assembly dumps correctly? Is there a situation that the hole may work in one direction (dumping air from the bladder) but not in the other direction (orally inflating)?

Possible scenario (I have personally seen this one):
There is some debris inside of the dump valve button mechanism that prevents the valve from opening all the way.

If you only test dumping air, it will work (you will hear air coming out, and call it a day)
But if you try to orally inflate, it will take much more effort and it will fill at a much slower rate (you don't want this underwater during a dive)

Test both ways. No reason not to do it, and valid reasons to do it.
 
It can also help as a repetitive drill that trains the brain to consider the oral-inflate option in an emergency.

Performed with the BCD in place / worn, it also ensures the LPI hose is not entangled and can actually reach the diver's mouth should it be necessary.
 
I always orally inflate my BCD prior to diving. Keeps me from using gas from my cylinder to fill the BCD. Just a habit that I have adopted.
 
I always orally inflate my BCD prior to diving. Keeps me from using gas from my cylinder to fill the BCD. Just a habit that I have adopted.

Never know when that precious .3 PSI might come in handy.

:D

But seriously, I "test" oral inflation the night before a dive; I fully inflate the wing before going to bed and check it in the morning to ensure that's it's airtight.
 
I must confess I am like DKL - especially shore diving I always inflate my BCD orally before the dive. I test inflate/deflate with the buttons as part of the buddy check when we kit up, but then orally inflate as we wade in. It is nothing to do with saving air, just a habit I developed. But as part of the buddy check itself? - I don't really see a benefit. _ Phil.
 
We teach it but in practice I don't think the risk of debris blocking it in one direction but not in the other direction is very high.

As an aside, I teach the buddy check in two major steps:

1) self test everything during set up, including all functions of the BCD and regulator
and
2) do the cross-check again once the gear is on.

Many instructors only do #2 but in my opinion, that's not enough given that in reality #2 sometimes gets glossed over. As a diver you always have full control over #1 and THAT, in my opinion, is the most important step of all.

If you really find it important to see if the oral inflator isn't blocked by some kind of debris that allows air out but not in, then do that in step #1.

YYMV.

R..
 
I always orally inflate prior to getting in the water, but the night before I do a positive pressure test on the wing to make sure it isn't leaking and that's done orally. I also orally inflate at the surface. Matter of habit as I was trained without a connected power inflator, so I orally inflate whenever I dive backmount, and always when at the surface.
 
Never know when that precious .3 PSI might come in handy.

Yup, you just never know. Better to have it and not need it, than to need it and not have it. :chuckle:
 
the risk of debris blocking it in one direction but not in the other direction is very high.

In the example I posted above, the debris was affecting the button, not just in one in one direction...basically not allowing the button to fully open the valve. And this is not that unlikely, specially on shore dives where sand/silt can get into the button mechanism.

Both deflating and inflating were affected.
But, deflation air flow is harder to discern(you still hear air coming out, and feel BCD deflating) than orally inflating (you feel how hard you need to exhale into inflator in order to inflate).
 
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