and the final reading could easily be misleading, perhaps dangerously so, possibly leading to central nervous system (CNS) oxygen toxicity or decompression sickness. One Analyzer? Really? Many dive resorts and liveaboards have one or two work- ing analyzers for the entire operation. Sometimes, that an- alyzer hasn’t had its sensor replaced in a year. That same analyzer might be tethered to the deck or passed around hastily as the crew rushes to get everyone geared up and off the dock on time. Improperly trained crew are often seen adjusting the calibration knob between samplings to return it to zero, which negates the accuracy of subsequent samples. TRAINING continued
proof ink and securely attached. Anything less invites dan- gerous mix-ups. Proper labeling is not just helpful – it's essential. The label should include: Oxygen percentage ▪ MOD (Maximum Operating Depth) ▪ Fill date ▪ Fill pressure ▪ Name or initials of the person analyzing ▪ Signature of the diver accepting the mix ▪ Flushing Fill Whips: The Invisible Contaminant
One of the more hidden yet widespread issues occurs at the fill station. Many resorts use long fill whips to fill cylinders at their dock or on their boats from storage tanks. But few flush these whips between fills, especially if the previous gas in those fill whips was air. If no final analysis is per- formed after filling, the result- ing mix may not accurately reflect the intended mix, poten- tially resulting in a higher nitro-
This practice contradicts the pri- mary reason gas analysis is con- ducted: individual accountability and precision. NOAA standards recommend using two calibrated analyzers when available. Not one for 30 people. Not one operated by a distracted divemaster who's juggling gear bags and departure times.
Every diver should analyze their own gas, record the result, and initial the contents label. If we cut corners here, we chip away at the foundational safety principle of mixed gas diving: know your gas. Sloppy Labeling = Lost Information Another disturbing trend is sloppy cylinder labeling. I've
Proper gas analysis in action: A DiveSoft Analyzer sampling through a 2 LPM flow regulator. This setup ensures consistent pressure against the sensor for accurate readings.
gen content. Every fill whip should be flushed thoroughly with the target gas before filling the next cylinder. Failing to do so means your mix is not what you think it is. Nitrox Membrane System Maintenance Mixing nitrox with pure oxy- gen can be inconvenient and costly, but membrane systems simplify and reduce the cost of nitrox blending. Regular mainte- nance is crucial; expert Danny Graham notes that membranes rarely fail if pre-filters are well- maintained and the heater works properly. Pre-filters should be changed every 250 hours with a refrigerated air dryer or every 50 hours without one. Neglecting maintenance can affect gas qual- ity, so it's essential to follow a strict schedule for pre-filter
seen tanks marked only with masking tape, "EANx" or "32" sometimes just a green band – no date, MOD, initials, or pres- sure. If a diver sets down their tank mid-dive, how does anyone know what's inside? Proper labeling is essential. Every label should include the oxygen percentage, MOD, fill date, pressure, name or initials of the person analyzing, and diver signature. Permanent labels should be filled out with water-
An incomplete cylinder label: displaying only a number and percent sign, with no indication of gas type, analysis date, or analyst. A casual shortcut that risks safety.
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