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AP Diving – Oxygen Cell supply

Due to interruptions in cell supply this year, steps have been taken to secure a second supplier. The cell from the new supplier, the same supplier as the Narked @ 90 cell, will have the designation APD16 and has a white label.

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Accuracy of cells
While the Narked @ 90 cell and the APD16 cell are very stable they have an unfortunate trait in that once the Inspiration scrubber warms up from top to bottom, which is 15 to 20 mins after the start of the dive, the cells read 0.05 bar higher than the actual PO2
i.e. while the cells display 1.30 bar ( the setpoint) – the actual PO2, measured on a calibrated fast response external analyser, is in fact 1.25 bar.
Although undesirable, this trait is repeatable and reliable and so is easily compensated for.. simply by reducing the High Gradient factor slightly.

Typically reducing the GF High by 5 is sufficient: If you use 90 normally – use 85; if you use 85 normally – use 80 etc.

Trimix Deco Software GF High Values 

APD14 APD16
95 90
90 85
85 80

If you have Nitrox decompression software you can achieve the same decompression safety level you are used to by changing the Conservatism level:

Nitrox Deco Software Conservatism 

APD14 APD16
1 3
2 4
3 5
4 5

Extreme dives will require specific fore-planning and calculation of appropriate GF High values.

Cell mixing
It is quite in order to use a mixture of the two types of cell, APD14 and APD16, but please bear in mind the dominant two will determine whether you need to adjust the GF high or not. i.e. if you have two APD14s and one APD16 then you wouldn’t need to make the GF high adjustment.