Why do a Bump Test?

Bump Test on a Gas Detector

Bump testing is the only way to ensure sensor and alarm functionality. A bump test is the process of briefly exposing sensors in a gas detector to an expected concentration of gas that is above the alarm levels set. The purpose of the bump test is to check for sensor and alarm functionality. It does not however check for accuracy which is ensured through calibration, which is a different process than bump testing.

All sensors have a life span and at some time will fail. Some will fail suddenly and some will fail over a longer period. Bump testing alerts the user of non-functioning sensors. This failed condition could be a loss of sensitivity, a loss of response time or both that could be caused from various factors. One of these is gases or vapours not being able to reach the sensor due to dirt or contamination. Bump testing will alert the user if a gas inlet has become blocked, even if the blockage is not visible to the human eye.

Toxic and combustible sensors have a typical output in clean air of zero. An oxygen sensor though should read around 20.9% volume in ambient air. Therefore, the only way to know if these sensors will respond to gas is by exposing them to gas. A bump test on a standard four-gas instrument will drive the gas readings up on your toxic and combustible sensors, while driving the reading for the oxygen sensor down.

Bump testing takes as little as 15 seconds up to around 3 minutes, dependent upon the model, to ensure your detector is working as you would expect.

If you bump test your unit and all 3 or more sensors fail bump due to slow response times this is quite often that the filters are blocked, although some sensors may not be working correctly either. In the first instance change all of the sensor filters and re-bump, if this now results in a pass then the problem has been sorted. If the bump test still fails return it to an authorised service centre.