Breathing the gas from your BCD

[Blackcrusader]

Ditch and don is much easier with a weight belt than it is with integrated weights, especially with a thicker wetsuit. Ask me how I know.

Yeah my scuba pro black is 8kg in the four inserts. I get out of my bcd I float to the surface.
Like you I have never had to wet my tank strap once I close the metal buckles never had a tank slip.

 

[inquis]

the pCO2 matters A LOT

You're correct the partial pressure is the crux of the matter, but I disagree as to how fast it builds up. As I see it, the PCO2 in your lungs prior to a normal exhalation remains the same regardless of depth. The number of molecules of CO2 produced in a given time is the same (being tied to metabolism), but the total number of molecules is far greater. This means the fraction of CO2 in the lungs during exhalation at 4 ATA is only 1%, so PCO2 is still 0.04 atm, just as it was at the surface.

Exhaling into an empty bag is equivalent to holding your breath as far as PCO2 buildup. Your lung volume decreases while the bag volume increases. As soon as you inhale again, it's all back in your lungs, just as if it never left. You will not be incapacitated in the span of a few breaths any more than you would by holding your breath for 15 seconds (roughly the time required for those breaths).

In the case that there is air in the bag, the CO2 will be diluted. A subsequent inhalation will result in fewer CO2 molecules in the lungs compared to holding your breath. However, this scenario is most likely at the end of the dive when the wing should be nearly empty and therefore of little benefit.

Realistically for a recreational diver, going for the surface with an open glottis (i.e., exhaling) is going to drop the PCO2 more quickly than messing about breathing from the wing. The latter also stands a good chance of screwing up your buoyancy, slowing (or halting!) progress to the surface. An even better option is to not be in such a situation to begin with, through proper gas planning and redundancy (either from a buddy or carry your own).

 

[Chavodel8en]

That's hardly an emergency.

Its enough of a problem that I would recommend that all divers wet their strap if it hasnt been wet in awhile. Not necessarily dunk it, a few well placed sprays from a water bottle will do.

 

[TMHeimer]

This thread is the first time I've heard of breathing (or sucking) air from the BC except in a dire emergency.

 

[Allen-1]

Its enough of a problem that I would recommend that all divers wet their strap if it hasnt been wet in awhile. Not necessarily dunk it, a few well placed sprays from a water bottle will do.

A month ago I was diving in Florida with a brand new BC. I forgot to soak the strap beforehand, and my tank was most certainly loose.

 

[tursiops]

A month ago I was diving in Florida with a brand new BC. I forgot to soak the strap beforehand, and my tank was most certainly loose.

This is completely normal with a standard cam strap. It is why peo[ple spend money to get the better/stronger kind of non-cam bands, such as made by multiple manufacturers. Here is an example.

Another solution is TWO cam bands, but it is still possible that both will slip.
Another solution is....wet the band before putting it on the tank.

 

[Allen-1]

This is completely normal with a standard cam strap. It is why peo[ple spend money to get the better/stronger kind of non-cam bands, such as made by multiple manufacturers. Here is an example.
View attachment 861714
Another solution is TWO cam bands, but it is still possible that both will slip.
Another solution is....wet the band before putting it on the tank.

This was absolutely failure on my part. I was taught to dunk the bc in order to wet the strap. I failed.

 

[BoltSnap]

This is completely normal with a standard cam strap. It is why peo[ple spend money to get the better/stronger kind of non-cam bands, such as made by multiple manufacturers. Here is an example.
View attachment 861714
Another solution is TWO cam bands, but it is still possible that both will slip.
Another solution is....wet the band before putting it on the tank.

Is the strap shown in the picture similar to Scubapro's tank strap in design/function? What brand is it please?

 

[tursiops]

Is the strap shown in the picture similar to Scubapro's tank strap in design/function? What brand is it please?

It is similar to ScubaPro's. It is a generic brand.

 

[inquis]

Is the strap shown in the picture similar to Scubapro's tank strap in design/function?

Lots of options. Aqualung makes a similar one for about $50, HOG has one for about $35, and OTG Dive (out of China) is around $25.