Nitrox Gas Blending Guide
Why Blending Matters
Nitrox blending supports dives that need controlled oxygen content. It is not a casual guessing task. Small pressure errors can shift the mix. Analyzer checks remain required before use.
Calculation Purpose
A calculator helps organize pressure steps. It estimates how much rich source gas enters first. It then estimates the top-off gas needed to reach final pressure. The method works for partial pressure fills. It also shows whether the source choice can reach the target.
Required Inputs
Good inputs matter. Enter the current cylinder pressure and its oxygen reading. Add the desired final pressure and oxygen percentage. Choose the source gas percentage and top-off percentage. Pure oxygen is often used as the source in partial pressure blending. Air is often used as the top-off. Other banked nitrox mixes can be modeled when values are known.
Dive Planning Values
The calculator estimates dive planning values. Maximum operating depth uses the oxygen limit. Equivalent air depth uses the nitrogen fraction in the mix. Planned depth oxygen exposure is shown as a partial pressure check. These outputs do not replace tables, training, or agency procedures. They simply give a clear numerical review.
Safety Notes
Use conservative settings when planning fills. Confirm that every cylinder, valve, whip, and regulator path is suitable for the oxygen percentage used during blending. Oxygen service rules are especially important when source oxygen enters the cylinder. Heat, contamination, and fast fills can create serious hazards. Follow laws and shop procedures.
Final Analysis
After filling, let the cylinder cool and mix. Analyze the gas with a calibrated oxygen analyzer. Mark the cylinder with oxygen percentage, maximum depth, date, and blender details. Compare the analyzer result with the calculator target. If the measured mix differs, use the measured value for all dive planning. The safest blend is the one that is verified, labeled, and understood.
Record Keeping
Recording each fill improves repeatability. Keep notes for starting pressure, analyzed starting mix, added source pressure, top-off pressure, final pressure, and final analyzer reading. These records help spot leaks, gauge errors, and analyzer drift. They also support training reviews. A clear log is valuable when several similar cylinders are filled during one session and later shop audits.