Yelled at for MOF

[boulderjohn]

Re mask around the neck concept, I've heard a story of a diver who suffered a broken neck when a large wave hit the boat he was standing on with his mask under his chin and his head hit the upper deck. I wonder, if this was a true story or an urban legend.

I've never heard of it, and I've been paying close attention to dive accident reports for 13 years now.

I used to wear it around my neck. I stopped doing it when I started wearing a bungeed alternate and there was no longer any room for it there. If I didn't have a bungeed alternate, it would be around my neck again.

 

[TMHeimer]

FinnMom, Don't think I'd trust putting mask in a pocket and even less inside a fin. Even though you haven't ever lost one, seems more riskier than any of the other methods mentioned. As well, I have seen someone drop a fin into deep water while near the boat.

 

[bmorescuba]

The inanity of the MOF rule aside, I would like to commend the OP (@stuartv ) for his use of the word "natatorium". I had never heard that word before. Scubaboard=Leanring! I plan to use this in pool classes now - welcome, students, to the Natatorium!

 

[TMHeimer]

Hi Tom
To illustrate why this isn't correct, turn on your tank valve and read your pressure gauge. Purge your regulator wide open and watch your pressure gauge. You will not see any drop in pressure. The gauge sees full pressure, always. You can save that air now and use it under water.

I am more likely to slide my mask to the back or down on my neck if I'm wearing a hood. If my hair is out, my mask is likely on my forehead when not in use. Comfort counts. I have a backup mask for other reasons. If I ever lose a mask on the surface, I'm good. MOF is a sign of nothing.

This isn't a dual thread but the title should have been, "things my OW instructor taught me that seem silly". Can we add the one about turning the valve handle back a 1/4 turn after opening it? All these things have caveats that are bigger than they are.

Whoa. I stand corrected, you're right. The gauge did go up to 3000--to be honest, I never in all these years thought to look at the gauge (it was usually pointed away from my face). Was the CD completely wrong? Can anyone heavy into physics give any reason why holding the purge open briefly would be any benefit in preventing an accident? Is it possible that this is another example (albeit an obscure one) of a myth that some past instructor heard and passed it on to that CD?

 

[boulderjohn]

Holding the purge valve open is often cited as a practice to use to prevent an air hammer effect hitting the second stage, which is what is being purged. It would have no effect on the SPG.

 

[kelemvor]

I've never heard of it, and I've been paying close attention to dive accident reports for 13 years now.

I used to wear it around my neck. I stopped doing it when I started wearing a bungeed alternate and there was no longer any room for it there. If I didn't have a bungeed alternate, it would be around my neck again.

I wear my mask around my neck with a bungeed alternate. Usually by the time I don the regulator I'm putting the mask onto my face anyway. However, I have on occasion had both around my neck both simultaneously and at the same time. It's important to make sure the mask is "on top".

 

[Dan]

Whoa. I stand corrected, you're right. The gauge did go up to 3000--to be honest, I never in all these years thought to look at the gauge (it was usually pointed away from my face). Was the CD completely wrong? Can anyone heavy into physics give any reason why holding the purge open briefly would be any benefit in preventing an accident? Is it possible that this is another example (albeit an obscure one) of a myth that some past instructor heard and passed it on to that CD?

You may notice on your 1st stage regulator there are HP (high pressure) ports (2 in Scubapro MK25) and LP (Low Pressure) ports (5 in MK25). The HP posts basically just tunnels connecting to the tank valve, upstream from the 1st stage chamber that drops the tank pressure to ~150 psig for the LP ports. By purging the 150psig to zero, you would not affect the HP port pressure unless the tank is near empty.

To avoid the slamming (hammering) on the SPG, HP hose and the SPG spindle internal (the part in the middle with 2 dynamic o-rings in the picture, below, has a tiny orifice to reduce the gas flow as you open the valve. Turning the valve slowly will also help in reducing the hammering effect.

 

[gypsyjim]

Even when diving my Kraken DH instead of long hose, bungied rig, I still place my mask around my neck to make sure it remains safe.
Yes, it can be a bit awkward, but it beats. losing a mask in a rough entry or exit

 

[boulderjohn]

in a rough entry or exit

If I am doing a rough entry or exit, the mask will be on my face.

 

[gypsyjim]

If I am doing a rough entry or exit, the mask will be on my face.

Agreed, most times, but if not on my face it sure is not perched on top of my head.