Gas detector calibration is the process of adjusting a gas monitor so its readings match a known, certified concentration of calibration gas. Done right, it keeps your instrument accurate and your records audit-ready. This complete guide walks through what calibration does, the equipment you need, the step-by-step process, frequency, and troubleshooting.
What calibration does: zero and span
Calibration has two steps. Zeroing sets the detector's baseline using clean zero air (or fresh air for some sensors). Spanning exposes the detector to a known concentration of span gas and adjusts the reading to match. Together they correct for sensor drift.
Equipment you need
- Calibration gas of the correct mixture and concentration, within its expiration date.
- A regulator — fixed-flow or demand-flow — with the correct fitting (C-10 is standard for disposable cylinders).
- The calibration cap and tubing for your detector.
Step-by-step calibration
- Turn on the detector and let it warm up and stabilize in clean air.
- Enter calibration mode and run the zero step.
- Connect the cylinder through the regulator and apply span gas for the specified time.
- Let readings stabilize; the instrument adjusts each sensor to the certified value.
- Confirm the pass, then run a bump test to verify alarms.
- Record the calibration date, gas lot, and result.
Calibration by detector brand
The exact menu steps and recommended gas vary by model. See the dedicated pages for the MSA Altair 4X, Ventis MX4, BW GasAlert Quattro and more on our calibration gas by detector index.
How often to calibrate
Bump test before each day's use and fully calibrate per the manufacturer's interval — often at least every 6 months. See how often to calibrate a gas detector.
Troubleshooting failed calibrations
- Won't span: check gas is in date, regulator flow is correct, and tubing isn't leaking.
- Drifts after calibration: sensor may be near end of life and need replacement.
- Wrong reading on one sensor: verify the gas mixture matches the sensor and the correlation factor is set.
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Frequently asked questions
What is gas detector calibration?
Adjusting a gas monitor so its readings match a known concentration of certified calibration gas, correcting for sensor drift.
What is the difference between zeroing and spanning?
Zeroing sets the baseline with clean/zero air; spanning sets the response using a known concentration of span gas.
What equipment do I need to calibrate a gas detector?
In-date calibration gas, a regulator with the correct fitting (usually C-10), and the calibration cap and tubing for your detector.