Nitrox Cylinder Label
Follow the steps with your cylinder in front of you: the tool fills in your label, you just copy it.
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Understand the nitrox label
Why every nitrox cylinder carries a label
A nitrox cylinder looks just like an air cylinder: only the label tells you what is really inside. It shows the analysed mix, the maximum operating depth, the pressure, the date and the initials of whoever analysed it. Before every dive, each diver analyses their own cylinder, even if the blender already did: the label proves the check was done and stops you diving a mix that is too rich for the planned depth.
Analysing your cylinder step by step
Wait until the cylinder has cooled down: a hot cylinder gives a false pressure. Calibrate the analyser in open air, it should read 20.9%. Open the valve gently, just a trickle of gas over the sensor, and wait until the reading stops moving. Compare it with the mix you asked for: this tool accepts a one-point O2 gap. Beyond that, analyse again, then tell the blender if the gap remains. The mix and maximum depth are always based on your analysis, never on the requested mix. For the fill itself, use the gas blender.
Maximum depth: 1 bar at the surface, +1 bar every 10 m
The deeper you go, the higher the pressure: 1 bar at the surface, then 1 more bar every 10 m. The oxygen partial pressure (ppO2) rises with it, and above 1.4 bar oxygen becomes toxic to the nervous system. The maximum operating depth (MOD) is where your mix reaches the chosen ppO2: with EAN32, 1.4 bar is reached at 4.38 bar, so 33 m; at 1.6 bar, the regulatory maximum, 40 m. The tool always rounds the MOD down to the metre. For EAD or CNS toxicity, use the nitrox calculator.
Safety rounding: label and dive computer
An analysis gives one decimal, the label a whole number. On the label, the O2 percentage is rounded up: 32.4% becomes Nx33, and the MOD is computed with that richer mix, so slightly shallower. In the computer, the tool rounds down: 32%, so the computer counts a little more nitrogen and plans a more conservative off-gassing. Then copy the label with a marker, stick it on the cylinder and fill in your line in the fill log, which you sign.
Frequently asked questions
What goes on a nitrox cylinder label?
The analysed mix (for example Nx32), the maximum operating depth (MOD) with the chosen ppO2, the cylinder pressure, the analysis date and the initials of the person who analysed it. Each item goes in its own box, in marker, and the label is stuck on the cylinder before the dive.
Do I have to analyse my nitrox cylinder myself?
Yes. Even if the blender has already analysed it, every diver analyses the cylinder they are going to use, then writes their initials on the label. It is the only way to be sure of the mix you breathe and of the depth you must not exceed.
How big a gap is acceptable between the requested mix and the analysis?
This tool accepts a one-point O2 gap: for a requested EAN32, an analysis between 31 and 33% passes. Beyond that, recalibrate the analyser and analyse again, then tell the blender if the gap remains. Either way, the label and the maximum depth use your analysis, not the requested mix.
How do you calculate the maximum depth of a nitrox mix?
Divide the maximum ppO2 by the O2 fraction to get the limiting absolute pressure, subtract 1 bar and count 10 m per bar. EAN32 at ppO2 1.4: 1.4 ÷ 0.32 = 4.375 bar, so 33 m rounded down. At ppO2 1.6: 40 m.
Why round the O2 percentage up on the label?
For safety: a richer mix gives a shallower maximum depth. If your analyser reads 32.4%, you write Nx33 and the MOD is computed with 33%, which keeps a small margin below the chosen ppO2.
What is the fill log?
It is the fill station logbook. The blender records the mix, their analysis and the pressure; the diver completes their line with the date, cylinder number, name, analysis, mix used, pressure and MOD, then signs. The tool prepares your line so you only have to copy it.