A bump test, also called a functional test, is a brief check in which a portable gas detector's sensors are exposed to a known concentration of test gas that exceeds the alarm setpoints. It confirms that the sensors respond and that the audible, visual and vibrating alarms activate. A bump test does not adjust the instrument.
Bump tests matter because gas sensors can fail or lose sensitivity without any visible sign, leaving a worker relying on a detector that will not alarm.
Bump Test vs. Calibration
- Bump test: a qualitative check that sensors respond and alarms work.
- Calibration check: a quantitative check that the readings fall within the manufacturer's accuracy tolerance when exposed to a known gas.
- Full calibration: adjusting the instrument so its readings match the known test gas concentration.
If a detector fails a bump test or calibration check, it should be fully calibrated, or removed from service, before use.
How Often Should You Bump Test?
OSHA's Safety and Health Information Bulletin on verifying calibration of direct-reading portable gas monitors, and the International Safety Equipment Association (ISEA), recommend a bump test or calibration check before each day's use, in accordance with the manufacturer's instructions. Additional testing is recommended if the detector is dropped, exposed to high gas concentrations, or exposed to substances that can poison sensors, such as silicones.
OSHA's permit-required confined space standard requires atmospheric testing with a calibrated direct-reading instrument, and bump testing is a common way to confirm the instrument is working before entry.
How to Perform a Bump Test Step by Step
- Check the test gas. Confirm the cylinder has the right gases and concentrations and is within its expiration date.
- Turn on the detector in clean air. Let it complete its startup and confirm it reads zero or normal oxygen.
- Connect the test gas. Use the manufacturer's cap, regulator or docking station.
- Apply gas. Flow gas until each sensor goes into alarm.
- Confirm alarms. Verify the audible, visual and vibrating alarms all activate.
- Record the result. Document pass or fail, date, instrument ID and the person testing.
- Act on failures. Calibrate and retest, or tag the instrument out of service.
Common Mistakes to Avoid
- Skipping the bump test because the detector was fine yesterday.
- Using expired or incorrect test gas.
- Blocking or covering alarm outlets during the test.
- Not keeping records, which makes it hard to prove instruments were checked.
- Ignoring a slow sensor response, which can signal a failing sensor.
How SMS360 Helps
SMS360's Audit Management module lets teams build simple equipment check forms, such as daily gas detector bump tests, and complete them on mobile devices in the field. Failed checks can become assigned actions, and completed checks are stored as records that can be reviewed across sites.
Frequently Asked Questions
How often should a gas detector be bump tested?
OSHA guidance and ISEA recommend a bump test or calibration check before each day's use, following the manufacturer's instructions. More frequent testing is advised after a drop, exposure to high gas levels, or exposure to sensor poisons.
Is a bump test the same as calibration?
No. A bump test confirms that sensors respond and alarms work, but it does not check or adjust accuracy. Calibration compares readings with a known gas concentration and adjusts the instrument if needed.
What happens if a gas detector fails a bump test?
The detector should not be used. It should be fully calibrated and bump tested again. If it still fails, it should be tagged out of service and repaired or replaced according to the manufacturer's instructions.
