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When I tested mine, it lost 100 psi in an hour when charged and turned off. Not something you'd stage in a cave overnight, but I would have no issue using it for a pony.

Some will bungee the "face" of the 2nd stage at the valve so it doesn't slip down when you're not looking. Could also do the mouthpiece, but that seems less secure to me.

Welcome! Local diving may be less than stellar, but that OW ticket opens the door to a new world. The vacation diving in clear/warm water will seem easy by comparison. Good luck today!

Sounds like progress, as there are many more CCR divers today. The lack of a denominator is a widely acknowledged issue.

FYI, grade E is basically nitrox 21 -- very clean. I don't know what "normal" air is graded. Also no idea if fire stations use the same grades...

Bungee once in the water. Until then, use a double-ender and a short loop of paracord around each valve.

I would suspect some byproduct of debris decomposition which doesn't dissipate due to lack of water movement. Chemical reaction is also possible, with the notable example of a hydrogen sulfide layer, but other compounds like calcium hydroxide are possible.

The trace amount of CO2 in ambient air enters the keg when opened, but is quickly reacted/removed and the reaction halted until opened again. I believe the impact on CO2 absorption capacity is negligible, as a single exhale has more CO2 than enters the keg when opened. Also, if your keg takes...

When horizontal, the bottle sags down and the wing lifts up, creating space for your hand to reach the dump valve.

That is at odds with a peer-reviewed journal article (reference below) that cites losing 30% of the surface volume at 10m, 60% at 60m, and 65% at 100m. I interpolate that as 51% at 30 m/100 ft. (Surface buoyancy of my XL 7mm is 16 lbs.) Losing a mere 2.5 lbs (as the video states) suggests a...

I workaround similar behavior with my CCR by telling the cylinder that cannot be deleted to use the transmitter. (Right-click the header row to turn on the Sensor column.) Edit the gas info accordingly. I don't know if this will work for a gas switch, but I suspect it might.

When calibrating, the computer locks in a conversion factor of actual/measured, so C=1.0 bar/43 mV. When later measuring 65 mV, that is multiplied by the conversion factor, yielding 1.51 bar for the displayed PO2. The relative error is (displayed/actual - 1) = (1.51/1.6 - 1) = -5.5%.

While Bobby's blog brings up many good points (especially the in-water test), it does neglect the impact of calibration. The example data he gives are 1.0 PO2 gives 43 mV (10% error from linear) -- 0% error after single-point calibration 1.6 PO2 gives 65 mV (15% error from linear) -- 5.5% error...

As would any class prioritizing proper weighting.

I should walk back my earlier reply a bit. I do check for nonlinearity (of which I regard current limiting to be a severe form) periodically throughout the dive by looking at the *change* in PO2 in a descent. After a descent by 10m/33 fsw (from any depth), the PO2 should increase by the fraction...

The calibration records the conversion between mV and PO2. Why not use a consistent and intuitive number (i.e., the PO2)?

Hitting 1.6 at the bottom doesn't necessarily mean it *is* 1.6 because of that potential nonlinearity. It's unlikely all cells would be similarly impaired and agree, but it's not impossible. Seeing them hit the value you *know* is correct eliminates all doubt.

Diving at altitude, l can only see up to a PO2 of 0.8 pre-dive, which is simply not close enough to the setpoint. My pressure pot is at 27 ffw.

I can certainly see @dmaziuk's point, it's the first stop that is in question. (Thereafter, it's just as you describe.) The simple implementation looks for the depth at which the GFL line crosses the (max) tissue saturation pressure. In this case, though, that would cross at a negative depth...

I believe you need at least 25 posts, and your above post was #25. Can you see the DM button now?