City Technology Ltd recommends users of portable gas detectors containing electrochemical or catalytic bead sensors conduct a daily ‘bump’ check before relying on the unit to verify an atmosphere is free from hazard.

A ’bump’ test is a means of verifying that an instrument is working within acceptable limits by briefly exposing to a known gas mixture formulated to change the output of all the sensors present. This is different from a calibration where the instrument is also exposed to a known gas mixture but is allowed to settle to a steady figure and the reading adjusted to the stated gas concentration of the test mixture.

For oxygen monitors a level of confidence that the unit is working adequately may be gained by exhaling over the sensor inlet and viewing the reduction in reading obtained. In many cases the reduction in Oxygen concentration obtained is sufficient to trigger the low oxygen alarm.