Equipment My first out of air situation

[scubadada]

Hmm, I DO appreciate the y=mx+b comment...that is my native language. And the problem seems to be mostly m.
If it were mine, I'd first try getting an RMA from Huish before trying to fiddle the electronics:

"All returns, service, warranty, and exchanges require a return merchandise authorization (RMA). To submit a request for an RMA, please send the following information to TAC@huishoutdoors.com:​

​

1. Dealer/customer number (if available)
2. Product information and specifications (i.e. part number, model, size, color, serial number, etc.)
3. Reason for return"

Good luck! Always nice to have a trustworthy spare, instead of something you'd only use on a pony.

That is a good idea, but I don't think Huish will service Aqualung transmitters, serial number prefix FC or FO rather than BM. Of course, nothing to lose by sending the information to Huish by email.

Question Post in thread 'Serial number prefixes on Pelagic Pressure Systems MH8A transmitters'

Mar 11, 2025

I communicated with Huish in January. They still service BM prefix transmitters except for flooding, which includes failure of the OPV. Here are 2 messages from Huish, the second to clarify flooding:

• scubadada

 

[Hatul]

i've not gone over every reply, but the question is what was the tank pressure when you got back on the boat. If the tank still had air it points to a blockage in the air flow, if the tank was empty it means you had a leak or the pressure gauge was bad.

And I agree with others that you should have immediately accepted the divemaster's octo when you found it hard to breathe.

 

[clownfishsydney]

My first thoughts from looking at the screen dump of the dive, a blocked intake on the valve. I have seen this happen before, person thought they were out of air but in fact the valve was blocked by rust particles. Did the OP check air pressure later or did anyone empty the tank and open it?

 

[tiacalypso]

I too would like to see the depth graph.

I don't use AI, but the air consumption graph does not make sense to me: it shows a remarkably constant slope, with ~100 bar used in ~35 min. This is regardless of changes in depth during decent or any changes in diver activity. For folks who do use AI: shouldn't there be greater variation in air consumption rate during decent and during the dive, and not a completely straight slope?

100 bar in say a 12 L tank is 1200 L - so the slope of the graph is 1200L/35 min = 34 L/m at 3 bar/20m. That equates to 11 bar/min on the surface: which is far lower than most experienced divers.

However assuming a more typical breathing rate for an inexperienced diver (say 22 bar/min) would empty a 12l tank in ~35 mins: close to what's seen.

As lizardland points out - I think the issue is with the AI/computer.

Cheers
Rohan.

I‘m an AI diver and my air consumption profiles are pretty linear.

 

[gamon]

I‘m an AI diver and my air consumption profiles are pretty linear.

You gotta watch the terminology or the nature of your reality will be in doubt.

You're a human diver who utilizes Air Integration.

 

[Subcooled]

Hello fellow divers. I'm a newcomer to the diving hobby. I got OW certified this year and have only 30 dives.

That's a nice amount of dives for the first year (or less).

At about 30 minutes from the start of the dive I checked my air and I had around 110 BAR.

Nice

At about minute 35 I noticed that taking a breath started to require a lot of effort

You spent 110 bar in five minutes??? Something does not add up.
Anyway, you are out of air. It has happened to me too, once unplanned at 60 ft.

I only had 3 BAR left . I immediately went to the dive master and gave him the out of air signal. He understood me and double-checked my computer. He offered me his backup 2nd stage,

Nice

but I didn't take it immediately, because I was still breathing (harder and harder, but still doable).

I have done the same thing myself, and it was not a wise choice. What if you would have lost contact with the dive master a bit later? You would have had absolutely no air!

You can indeed do a free swimming ascent from 60 feet, no problem, but it is always better to have one or two extra options.

I still had a strange feeling of uncertainty.

That is very wise unless, of course, it turns into panic.

We made it to around 5 meters and we started our safety stop.

A safety stop is completely optional. It is not a mandatory decompression stop. You might have continued directly to the surface, or if it feels better, made a short stop. Stopping, of course, gives a more gentle resurfacing experience to the body.

At minute 2 of the safety stop I had the same feeling again - taking a breath required a lot of effort and I was not able to take a full breath - clear sign the DM's tanks was running low.

Very low, actually.
WTF was he/she thinking allowing this scenario to take place?
PAID dive masters are supposed to be professionals.

I am loosing sleep over what actually happened.

Relax. I have ran out of air at 60 feet and the swimming ascent was quite nice. As the ambient pressure dropped, the relative overpressure in my scuba tank grew double upon ascent to the shallows and I could even waste some gas on a completely unnecessary safety stop.

Freediving 25m or 75ft is very much doable, too.

Maybe something blew up and all of my gas went out.

"Blew up" means bubbles and noise.

I was hearing bubbles going out.

Yes.

I don't know what to trust - what I heard or what my computer is telling me.

You should trust both. Hearing is more susceptible to misinterpretations but it is worth noting, though.

According to the DM it was sort of malfunction in the regulator, because it was due for a service.

Ouch! I once dove with a regulator that had not been serviced in five years and it was hard to breathe, but it still gave air on demand. On demand, indeed, as I had to suck. But it was different from the growing breathing resistance over a couple of breaths of an out of air situation.

I am confused

Me too

I am also wondering if I tightened the 1st stage to tank good enough. These were DIN tanks.

If you did not, you would have heard constant bubbles.

what can I do to reduce the risk of that happening again?

You can reduce the risks by relaxing.
These things sometimes happen and they are not a big deal if you are prepared and aware of your surroundings and situation

I am buying a set of personal regulators so that I can be responsible for cleaning and maintaining them.

 

[sena_akutsa]

At about 30 minutes from the start of the dive I checked my air and I had around 110 BAR. We were at 22 meters. At about minute 35 I noticed that taking a breath started to require a lot of effort, Looking at my computer I saw that I only had 3 BAR left We made it to around 5 meters and we started our safety stop. At minute 2 of the safety stop I had the same feeling again - By the end of it there was no air inside the tank.

According to my computer I lost my air in a very short time. I don't know what to trust -
According to the DM it was sort of malfunction in the regulator, I am also wondering if I tightened the 1st stage to tank good enough. These were DIN tanks.

View attachment 914044

Hello,
like others said, if there was an air Leak then you, someone else from your group, or the dive master would notice that.

I encountered 2 mechanical SPG that went bad in our club within 3 years,
but can say nothing about your "air integrated" transmitter reliability.
Still your graph looks like a mechanical problem encountered (like clogged valve).

....what bothers me more is:
your DM and You "emptied his tank" at the safety stop;
with which pressure the DM was planning to start the group ascend if you didn't run out of air ??
50 bar is more than enough for 2 buddies to stay more than 7 min at a safety stop depth, tried many times with a 12L tank.

 

[bipolarbear]

You've got 30 dives, and all your own gear, yet you consider yourself a newbie and you act like one.

Not monitoring your air, not taking the DM's octo when you were already breathing hard were huge mistakes, offering your primary reg to the DM to see if you were doing something "wrong" when you were obviously OOA, completing your safety stop when you AND the DM are BOTH out of air were others, although that last one is on the DM although it's hard to believe there is such a level of incompetence in a supposedly trained professional that would require both of you to make an emergency ascent from safety stop depth and risk an AGE because you just HAD to complete that last 60 seconds of safety stop following a relatively shallow dive. I don't think I've seen this level of combined ineptitude in a single dive.

Where was your dive buddy when all of this was happening?

I think this is unfair on OP.

Based on the the pressure chart the OP has provided (which no one seems to bother reviewing), and the fact that there was no catastrophic gas loss reported, it seems quite clear that what OP experienced was some obstruction / clog in either the valve assembly or the first stage itself. Can be caused by rust, water ingress or other contamination.

We can discount tank roll off (which would have become more breathable as OP shallowed up), free flow / gas rupture and OP inexperience (because as they rightly point out, it's not humanly possible to consume 110 bar from an AL80 i.e. over 1000L of gas in two minutes at 20m).

Agree that safety stop should have been skipped in these circumstances. Also very confused how DM did not have sufficient gas to air share a diver to the surface at the halfway point of a recreational dive. More blame should be attributed to the DM than to the OP here.

OP should have the tanks and first stage inspected. If there is contamination then second stages should probably be looked at also in case some of the particulate has migrated up to the regs.