If you manage portable gas detectors, two questions come up constantly: how often should you bump test, and how often should you run a full calibration? Here is the straightforward answer, what the standards actually say, and the factors that should make you calibrate more often.
The short answer
- Bump test: before each day's use.
- Full calibration: follow your manufacturer's recommended interval — many specify a full calibration at least every 6 months, and some recommend as often as every 30 days for demanding environments.
What OSHA and ISEA say
OSHA's safety guidance and the safety equipment association (ISEA) state that a bump test or full calibration of direct-reading portable gas monitors should be performed before each day's use, in accordance with the manufacturer's instructions. The instrument manufacturer's manual is the authoritative source for the full-calibration interval — always defer to it, because sensor technology and warranty terms vary by model. See our complete gas detector calibration guide for the procedure itself.
Factors that shorten the calibration interval
Calibrate more frequently when any of these apply:
- The detector was dropped, exposed to a high gas concentration, or alarmed.
- It operates in extreme temperatures, high humidity, or dusty/dirty atmospheres.
- It is exposed to sensor poisons or inhibitors (silicones, solvents, high H2S).
- Readings drift, or a bump test result is marginal.
- Your site or compliance program requires a tighter schedule.
Bump test vs. calibration cadence
A daily bump test is your routine confidence check; periodic calibration is the deeper correction. If a detector ever fails a bump test, calibrate it immediately rather than waiting for the scheduled interval. Learn the difference in what is a bump test.
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Frequently asked questions
How often should a 4-gas monitor be calibrated?
Follow the manufacturer's interval — commonly at least every 6 months — and bump test before each day's use.
Is calibration legally required?
OSHA references manufacturer instructions and ISEA guidance; following the manufacturer's bump and calibration schedule is the recognized practice.
Should I calibrate after dropping a detector?
Yes. Impact, high-gas exposure, or any alarm event are reasons to calibrate before next use.