Gas Detector and Analyzer Calibration Guide
Gas detectors and analyzers require regular calibration to ensure accurate and reliable gas concentration measurements for personnel safety and process control.
I. Calibration Fundamentals
- Calibration Gas: Use certified calibration gas mixtures with traceability to national standards. The calibration gas concentration should be in the upper half of the instrument measurement range.
- Zero Gas: Use clean air or nitrogen that is free of the target gas and interfering compounds. Ambient air can be used for oxygen sensors.
- Calibration Frequency: Calibrate at intervals recommended by the manufacturer. Critical safety applications may require monthly or more frequent calibration.
- Bump Testing: Perform a bump test before each day of use to verify the instrument responds correctly to a known gas concentration. This is a functional check, not a full calibration.
II. Calibration Procedure
- Preparation: Allow the instrument to warm up in clean air. Verify the battery is charged.
- Zero Calibration: Apply zero gas and allow the reading to stabilize. Adjust the zero trim until the reading indicates zero.
- Span Calibration: Apply the calibration gas at a known concentration. Allow the reading to stabilize. Adjust the span trim until the reading matches the calibration gas concentration.
- Verification: Remove the calibration gas and allow the reading to return to zero. Re-apply the calibration gas and verify the reading remains within acceptable tolerance.
- Documentation: Record the calibration date, gas concentrations used, as-found and as-left readings, and the technician name.
III. Maintenance
- Check calibration gas expiration dates; expired gas causes inaccurate calibration
- Inspect the regulator, tubing, and calibration adapter for leaks or damage
- Replace sensors at the end of their expected service life, typically two to three years for electrochemical sensors
- Keep the instrument clean and protect from extreme temperatures and humidity
