Dental chair ramblings.

[Kern]

Yes. It's something I've observed on hundreds of occasions, when teaching scuba classes.

It's the sole reason why divers are taught to press the top of the mask against their heads when performing a mask clear. What did you think the reason for that was?

If you orient your mask in the right direction, touching the mask is unnecessary. If your taught skills on your knees, & not to orient your mask correctly, maybe you need to.

 

[DevonDiver]

If you orient your mask in the right direction, touching the mask is unnecessary. If your taught skills on your knees, & not to orient your mask correctly, maybe you need to.

We're talking about accident/non-deliberate exhalation from the nose are we not?

The mask is orientated wherever the diver happens to be looking when breathing.

With specific regard to training/mask clearing... the diver is looking forwards (head horizontal) to clear. That doesn't change whether they are on their knees or in horizontal trim.

 

[Kern]

If the mask is properly fitted, with the straps at the right tension, the pressure differential will not allow anything more than a drop or two to enter the mask when exhaling through the nose.

I regularly, & deliberately exhale through my nose to equalise the pressure inside the mask with the ambient water pressure. No water enters the mask.

To clear a flooded mask, I role while exhaling, forcing the water out of the mask. While looking up, all of the skirt against the face is the lowest part of the mask. No hands required.

If exhaling while looking forward & holding the top of the mask firmly against the forehead wont allow water into the mask, exhaling while looking in any direction without holding the mask will also not allow water into the mask. In both instances, the pressure differential prevents water from entering the mask, not holding the top of the mask. Of course if you want to force the water out of the mask while looking forward, you have to ensure the gas can only escape from the lowest part of the skirt by forcing it against the forehead.

While gravity points in one direction, water pressure points in every direction.

 

[DevonDiver]

It depends on the volume of air leaving the mask. Over-pressure isn't enough to prevent some water entering. I respect your right to believe otherwise, but as I've said - it's something that I've encountered (and remediated divers on) hundreds of times.

In 'theory' no water should ever enter any mask, because it can be over-pressured through regular nasal exhalation. Funny how that doesn't happen in reality?

 

[Kern]

Funny how it's worked in my reality for almost 20 years. Funny how when we ascend, the internal mask pressure increases & gas vents to equalise pressure, that they don't flood.

I usually remediate others with the problem by suggesting the loosening of the straps to prevent skirt distortion, &/or getting a mask that fits better.

 

[Linedog]

OK, I have tried 9 different masks, I now have a Scubapro frameless that fits like a dang suction cup to my face. When I exhale I'm sideways, face down, face up, hell I'm even upside down! it not a full blown flooding issue, it's a slow leak. If I did nothing about it my mask may be "full" when I'm done. It's just enough to be annoying.

 

[DevonDiver]

Funny how it's worked in my reality for almost 20 years. Funny how when we ascend, the internal mask pressure increases & gas vents to equalise pressure, that they don't flood.

I usually remediate others with the problem by suggesting the loosening of the straps to prevent skirt distortion, &/or getting a mask that fits better.

So...you're saying that any leaking mask is the result of bad fit or over-tight straps?

I've used the same mask for the last 9 years. It has a velcro strap... the fit of which hasn't changed in the last 9 years.

Can you explain how I can make it leak by exhaling from my nose?

From the sounds of it... you never get water into your mask when diving. Is that true? You've not done a partial mask clearance in 20 years?