What is the purpose of instrument calibration in industrial hygiene monitoring, and how is routine calibration typically performed?

• A. Calibration is unnecessary; measurements are valid without it.
• B. Calibration ensures accuracy and reliability; perform a span/gas calibration with a known standard and a zero check before and after sampling, plus periodic recalibration per manufacturer guidelines.
• C. Calibration only checks software; hardware remains unchanged.
• D. Calibration is only required for new instruments.

Answer: (B)

Calibration is about making sure the instrument’s readings reflect reality. In industrial hygiene, accurate measurements are essential for protecting workers, so the device must be adjusted against known references to account for drift, sensor aging, and environmental influences. Routine calibration typically includes a zero check and a span (gas) calibration using a known standard. The zero check uses clean air to confirm the instrument reads near zero (the baseline), confirming there’s no offset drift. The span calibration exposes the instrument to a precisely known concentration and adjusts the response so the reading matches that standard over the measurement range. Doing this before and after sampling helps ensure you start and end with accurate results and that the device wasn’t off during the run. Periodic recalibration per the manufacturer’s guidelines keeps the sensor performance reliable over time, since sensors can drift between calibrations. Calibrations should also be traceable to certified standards and properly documented.

The other options fall short because calibration is essential for accuracy, not optional; it addresses hardware and sensor response (not just software) and is not something only new instruments require—drift can occur anytime, so routine calibration is needed throughout a device’s life.