Ice diving full face mask free flow

[oldflounder]

Well I finally had my first freeflow with the ffm the other day. I am just writing this to share my experience with others that may be interested in acquiring one and trying to decide whether or not to go for it. I have been using the mask as much as I can this winter and really love it in the cold water.

I was out this past Saturday, got geared up and entered the water. The air temp was 36* and the water was the same at 36. I was shore diving in a lake with open water along the shore. I got the mask on and got down about 5' and could hear bubbles leaking out around my cheeks. I fussed and fussed with it, thinking it wasn't sealing with my latex hood where it's over my chin. I yanked it away from my face several times trying to get a better seal [not even noticing the cold water on my face by the way.] I just couldn't get it to seal. It had a lot of positive pressure inside the mask but was not very forceful. I surfaced to see what was going on and realized it was freeflowing because the air would not stop escaping from the mouthpiece.

Again I repeat that it was not escaping any quicker than if I just held the purge button down 3/4 of the way. I could have easily breathed off it while surfacing from depth if I'd had to. I now realize that even though you still need to carry a spare mask and pony bottle with you, in a freeflow you can probably still function with the ffm staying on your face without freaking out and ripping the mask off. And then trying to grab the spare mask and octo. All you have to do is keep your face pointed down toward the bottom and the gently escaping air stays against your face with plenty to breath. The emergency situation, where you rip the mask off, comes into play when the air has all escaped!! How long this takes to happen in a real situation depends upon all those factors [depth, size of tank/how much to start with when freeflow occurs, breathing rate, length of safety stop, etc., etc..]

I think the majority of the time that I would experience this situation in my style of winter diving would be as I am first starting the shore dive and am relatively close to the surface. The big problem I see with the ffm is that (1) you must start breathing through it while still above the surface and exposed to the air and (2) as you enter the water with the mask dangling/hanging off you somewhere, the reg will flow if it is upside down as it enters the water, if it is tuned properly. If you are not aware that it is flowing as you are getting into the chest deep water and putting on your fins, you are just begging for a freeflow. When I got up on shore and removed the unit, the first stage was totally incased in thick ice from the pressure release effect sucking the "warmth" out of the surrounding metal.


Lots of good lessons learned...............

 

[lowviz]

Nice write-up.

...//... [not even noticing the cold water on my face by the way.] ...//...

-funny how true that is, focussed on other things...

 

[mntdiver]

A free flow should never be a catastrophic event. You're mask will, as you experienced, exhaust the excess gas. Use the gas as it goes by and terminate the dive safely. One thing often not taken into consideration is that it may not be your second stage that's frozen, first stages can freeze as well. This turns your second stage into an expensive OPV. Also, you might try making it a habit to not flood your mask prior to diving. Easily done with a mask fitted with an ABV (Ambient Breathing Valve), less so with a basic ffm, such as a ScubaPro or Mantis.

 

[oldflounder]

A free flow should never be a catastrophic event. You're mask will, as you experienced, exhaust the excess gas. Use the gas as it goes by and terminate the dive safely. One thing often not taken into consideration is that it may not be your second stage that's frozen, first stages can freeze as well. This turns your second stage into an expensive OPV. Also, you might try making it a habit to not flood your mask prior to diving. Easily done with a mask fitted with an ABV (Ambient Breathing Valve), less so with a basic ffm, such as a ScubaPro or Mantis.

mtndiver --- Thank you for the advice. My 1st stage was freeflowing because it was totally incased in ice when I took the unit off. But I think the 2nd stage on the ffm started it because it is too finely tuned. This weekend I am going to have it "detuned" a little to see if that stops the auto purge when it gets turned upside down in the water. I can also remove the ambient plug in the mask as you suggest and don the mask while it is still above the surface. That might help.

Stay tuned for further updates.

 

[mntdiver]

One of the primary issues with a mask like the ScubaPro and Mantis is the location of the purge in the chin. When you're in a face down attitude, with the second stage diaphragm being lower than the purge, the hydrostatic pressure will cause the reg to free flow. You could have the regulator detuned to reduce this, however, you might end up with a bit of a pig of a regulator. Have a look at your mask, if you're looking straight down, note the position of the diaphragm in relation to the purge. Depending on the second stage you've mounted to the mask, it could be a couple of inches. When you're diving, this is the hydrostatic pressure that is influencing the regulator. As an example, if your second stage is cracking at about 1.5 inches of water column, as measured on the magnahelic, and the diaphragm is 2.5 inches below the purge, then the free flow will be initiated. The pressure blowing through the mask will be equivalent to the distance. This is why masks such as the Guardian, Divator and Atmosphere are designed to exhaust through the main diaphragm. You could resolve this by blocking the purge. I've used a nickle in the purge of a Mantis mask before. But then you'll have difficulty clearing the mask, leaving a bit of a puddle in the chin. You can also use the dive/pre-dive to restrict the gas, but this means a lot of work just to be able to look around when you're diving.

 

[oldflounder]

One of the primary issues with a mask like the ScubaPro and Mantis is the location of the purge in the chin.

Thank you mntdiver - My Scubapro doesn't have a purge in the chin. Maybe the older models do. I took it out again this past Saturday and was more careful with it. I decided not to get it detuned [at your recommendation] and entered the water carefully so that it didn't get submerged and possibly start another freeflow. Air temp 40* - water 41. This time I put the mask on carefully and used the ambient air valve to breath so that I wasn't using the reg. I put the plug back in after submerging and spent 1/2 hour in the shallows without the freeflow re-occurring. I also learned that the mask does not flood
if the plug is not in place. The valve is oneway and if I suck on the reg hole it stays shut. I don't know how depth affects it though. I have to experiment more with this valve operation next time out.

 

[CristiC]

Two days ago I witnessed a free-flow while diving under ice in a mountain lake at high altitude. My buddy was wearing a Scubapro FFM. We were about 10 yards from the hole, just below the ice and the water temp was 36. His second stage was leaking air with a steady flow, not much, like continuously breathing out.

I asked him several times "let's get out of here", he denied and wanted to stay longer, since we were so close to the hole and he had plenty of air left. After two or three minutes our line tender pulled us out, in disregard of line signals, because he saw the bubbles and assumed free-flow and miscommunication.

That was just in time because the first stage, a piston type, froze shut and my buddy was in an out-of-air situation. Even worse, the BCD and drysuit were connected to the same regulator and my buddy was not able to inflate anything. All went well in the end.

Later he told me that he had no spare mask and was not willing to take off his FFM in cold water, in fact he never had done it before.

Lessons learned:
1. On free-flow abort the ice-dive immediately.
2. Good communication is very important, there should be no slack in the line, the tender should be a trained ice diver himself.
3. Have a spare mask. When wearing a FFM one shall be prepared to doff it in cold water and then don the spare "normal" mask.
4. There should be a redundancy regarding buoyancy compensators. BCD and drysuit LP hoses should go to a different first stage each.
5. Inexperienced divers with free-flowing regs tend to disregard buoyancy while dealing with the FFM problem.
The buddy should stay very close and keep the depth for both.

 

[oldflounder]

That was just in time because the first stage, a piston type, froze shut and my buddy was in an out-of-air situation. Even worse, the BCD and drysuit were connected to the same regulator and my buddy was not able to inflate anything. All went well in the end.

Thank you for posting thatCristiC -- I have understood that regs usually freeze in the open position. It's important to know otherwise.

I have been connecting my drysuit hose to my pony bottle, but now I think I will connect my BCD up also in case I need quick surface flotation in an emergency.

Never mind I said that---the hose routing would get too complicated. Inflating the drysuit a little on the surface would do me if need be. At least it would give me time to manually inflate the bc.

 

[CristiC]

Now I talked to my buddy on the phone to make sure that the first stage froze shut. It did not. There were three distinct problems, all happening at the same time.
1. There was a small continuous free-flow and he had air to breathe all the time, a little too much air in fact.
2. The temperature on the surface was 3 deg Celsius and it dropped to 1 deg Celsius at 30 feet depth. While diving down the drysuit inflation button froze stuck, my buddy was not able to inflate his drysuit.
3. The BCD inflator froze and my buddy was not able to deflate the BCD. It got a permanent inflation and leaked air through the overpressure valve. He rose to the surface and dragged me up too since I was attached to the buddy-line.

We were many divers at that event, alternatively playing the role of diver, line tender and safety diver in turns. My buddy was waiting on top in the cold for some time prior to our dive, as safety diver. That may have influenced point 2 and 3 above.

You were right, the regulator froze in the open position, as was the BCD inflator.

Again, to be very clear about redundancy: There should be a primary circuit that is composed of a first stage, a LP hose to the BCD/wing and a hose to the second stage on the FFM and nothing else.

The secondary circuit is on a separate valve/ different bottle. There should be another first stage with a LP hose going to the drysuit, an HP hose going to the pressure gauge and a hose going to the other second stage. This one won't be called an octopus, it's a secondary second stage.

Do not connect the BCD and the drysuit to the same first stage or you will loose redundancy. It doesn't matter if it is the pony bottle or the main one. BCD and drysuit inflation should be independent generally, when wearing a full face mask or not.