Why would a reg become difficult to breathe from?

[happy-diver]

And here we see people raising it can happenses, and presenting them to a naive unsupecting public
who already with their lack of knowledge have enough concerns about diving without adding fantasy

Engagement is why we're here, sometimes stuff happens because you were there and so was the stuff

 

[Angelo Farina]

Another possibility, which I have seen in the past. It has nothing to to with the the regulator itself:

Debris from the cylinder can partially block the dip tube of the valve. On aluminium cylinders a big ball of aluminium-oxide greater than 3cm in diameter can easily develop. On steel cylinders like ECS, the base metal does not form a powder, but big flakes of rust, very thin and a good 3cm long.

If a diver goes down head first or does a overambitious back roll, this debris can fall on to the dip tube, partially blocking it. As there is no imbalance between the cylinder and the inside of the valve until a diver inhales, the debris can just sit loosely lodged in the tube. Breathing becomes harder as the diver empties the air from inside the regulator and hoses, while some air may bleed past the partially blocked tube. If the pressure imbalance gets high enough, the debris may get dislodged and usually broken up into smaller pieces, allowing more or less normal breathing.

Chances of this are very low. I thought the first time I have seen it happen it's a one in a billion chance, but it did happen again at a later stage. It of course has nothing to do with you using the pre-dive switch. In a situation like this, the person usually abruptly moves his body, which may also help to dislodge whatever is in there.

As I could not believe it after I have seen it for the first time, I experimented with an old ECS cylinder in the workshop and sure enough, if the bottle is flipped as in a fast back-roll, this can happen.

Without the cylinder turning upside down at some stage, this is impossible to happen, as the air would not suck the debris up the cylinder.

This happened to my son with a rental tank (steel, very old, and we do not have VIP here in Italy). It was not the first case I heard of, and it is actually one of the reasons suggesting a yearly VIP.
The clogging material was rust.
It forced a complete rehaul of the reg, including both second stages.
However, my son did "the right thing" switching to the secondary air source. Which indeed was also not functional, as the clogging was at the filter inlet on first stage. However I did find some of that fine rust powder also inside hoses and second stages.
It is not clear if the OP switched to the secondary air source, and if this was working or not...

 

[Mobulai]

I had to suck pretty hard, but I did get air.

So high cracking effort „high“ flow; kinda like a Poseidon reg (so I hear about them)?

 

[34109411]

mmm, diaphragm of second stage got stuck ?

 

[buddhasummer]

mmm, diaphragm of second stage got stuck ?

How does that happen?

 

[lexvil]

There are countless possibilities but without the reg in hand all you’ll get is speculation.

best way to minimize the chance of this happening again is to bring a complete second regulator with you, yours that you maintain and use in rotation with your first one to stay aware of its condition.

if this were a spider or chunk of other random material you should have some sort of respiratory infection by now, or not.

 

[34109411]

How does that happen?

debris, torn out etc... it was a rental if it s salt water you could have accumulation of salt and it could get stuck...it could be one hypothesis

 

[Divin'Papaw]

There are countless possibilities but without the reg in hand all you’ll get is speculation.

best way to minimize the chance of this happening again is to bring a complete second regulator with you, yours that you maintain and use in rotation with your first one to stay aware of its condition.

if this were a spider or chunk of other random material you should have some sort of respiratory infection by now, or not.

This is how I mitigate this risk. I have a complete 2nd reg set with me.

I also have zero HP hoses on any of my regs … primary, backup, & pony. Just a transmitter directly attached to the 1st stage. If a hose is going to blow, it’s typically the HP hose.

 

[MidOH]

I bring a stripped extra 1st stage on warm water vacations. All plugged up, with the wrenches in my checked luggage.

Can remove my spg and use just my transmitter. If I lose a 2nd stage, I'll dive with just one.

Non-air travel, I bring a whole extra set, and a pony.

 

[scubadada]

This is how I mitigate this risk. I have a complete 2nd reg set with me.

I also have zero HP hoses on any of my regs … primary, backup, & pony. Just a transmitter directly attached to the 1st stage. If a hose is going to blow, it’s typically the HP hose.

Button gauge on your pony or also a transmitter?