Zero vis air management

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muddiver

Contributor
Scuba Instructor
Divemaster
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Location
West Coast USA
# of dives
500 - 999
Ok, dumb question time.

Since most PSD teams use SCUBA to do search, rescue and recovery work, how does your team train to monitor the amount of breathing gas remaining in the diver's cylinder during a zero visability dive? And I am not talking a low vis 6" to 3' dive, I am talking a "you run into things and really can't tell what they are" dive.
 
The black water or no-lights method used by some military guys is to dive a set of doubles with the isolator closed.

When you run out of air, you know you have used up 1/2 of your air. Open the isolator a few seconds and then close it. When you run out again you are down to 1/4 of your air.

What would be a much better system is the vibrator and bell sort of gizmo on a fireman's breathing apparatus. Is there an underwater version of that?
 
About 80% of our dives are black, mostly all are under 30 ft, even in the worse vis i dont think its ever been a problem to see your gauge.Once you wipe the muck off the glass.I have had to hold it up to my aga with a light, but really were most of our bad call outs are if you run out you just stand up and switch out.
 
There is a need for the divers to take some responsiblity for their air consumption rates and know what time period they can achieve from the cylinder size they dive. Due to thermal considerations along with stress of recoveries, our policy has been to limit divers to 20 minute intervals. (Note that our dives are at worst 40' in depth) Depending on the number of divers and conditions, they will have an opportunity to get back into rotation after a break and a fresh tank. If somone burns through an 80 in less than 20 minutes, they probably should not be participating in these types of dives.

By implementing this time limit, it has worked out well for us.

Dan
 
Due to thermal considerations along with stress of recoveries, our policy has been to limit divers to 20 minute intervals.

By implementing this time limit, it has worked out well for us.
For zero viz dives where the diver cannot see a watch, I assume you are doing tethered dives and terminate the dive via line pull signals. Correct?
 
Not a PSD and never dove absolutely zero vis, so I hope you'll excuse the noob question, but if you have a fluorescent gauge, can't you press the gauge against your mask? Or are there reasons not to do this?
 
If we are in zero viz and using self contained, we limit each diver's bottom time to 25 mins. We usually work with surface supplied air in zero viz when we can not read our guages. We pretty much know what body of water is going to require each system.
 
Sounds like a good place for a J-valve or a scubapro Mk7.
 
https://www.shearwater.com/products/swift/

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