Calibration of gas detectors is vital to be sure that they are in good working order and able to alert the user to gas hazards in their vicinity. A calibration is a “resetting” of the detector’s response against a known concentration of target gas, in a balance of synthetic air or nitrogen. This will determine the relationship between the detector’s reading and the actual concentration of the component gas of interest. Adjustment involves modification of the detectors response to bring the reading into line with what is expected while exposing the instrument to the known source. This is fundamentally different to bump testing which is a brief exposure to gas in order to verify that the sensors respond within a specific boundary and the detector’s alarms function properly.