Free flow at depth

[rjack321]

Many fill stations don't meet the maximum allowable "normal" moisture limits of 24ppm (grade E air). For true ice diving the moisture content should be as low as possible and below these concentrations.

In the tropics air >24ppm moisture is indicative of filter breakthrough. Hopcalite which is a catalyst removing CO won't work and at even higher moisture levels the activated charcoal will become saturated and allow gaseous hydrocarbons to pass. Wetter still oil mists will pass the filter. Many filters in the tropics are so bad they are at the oil mist passing stage and the resulting "breathing gas" which includes CO, water, gaseous hydrocarbons, and oil mists is completely unfit to breath leading to fatalities.

 

[dpaustex]

Interesting discussion.

The physics of air (or any gas) is that it cools upon expansion. Compressed gas house air-conditioners use this very principle by first compressing the gas, then expanding it through an expansion valve inside the home, inside a set of coils, where cooling takes place.

The same thing happens in your regulator. The job of the first stage is to do the intermediate step of reducing the high-pressure gas in your cylinder down to a working pressure that your second stage can handle, yet is high enough to keep working at depth.

However, at the surface, the pressure differential between your tank and ambient pressure is the greatest difference (there is no water pressure), so the maximum expansion - and therefore cooling - of the gas is taking place. If you add in temperature differentials, you could very well have caused internal icing.

It could have been a part in your first or second stage. I don't know if you have a piston reg or a diaphragm. I don't know the condition of all of your seats, seals, etc., and if it is environmentally sealed.

Like others have posted, if you have excess moisture in the air (again, goes to fill standards of your gas supplier), this moisture can freeze up as the gas goes through the first stage, wrecking havoc on your setup.