Personal Gas Detectors

Calibration and Bump Testing

What is Calibration

Every gas detector contains sensors that take readings of their surrounding atmosphere. Over time, the visual reading displayed on the detector can drift and lose accuracy. In order to avoid getting inaccurate readings a detector needs to be recalibrated regularly. Calibration does not replace a bump test, which is another important component of a gas monitoring program.

Calibration involves applying a known concentration of gas to a detector while it is in calibration mode. The instrument's electronic display reading will adjust to match the desired value based on the concentration being applied, thus realigning the accuracy of your display.

One of the most frequently asked questions about calibration is how often it should be done. The amount of time between calibrations can vary, but should at minimum follow the manufacturers' recommendations. You may need to calibrate more often based on provincial regulations or your own company policies. The date and time of each detector's calibrations should be recorded and tracked throughout the life of the detector.

Docking modules, such as the MicroDock II from BW, can simplify this process by automatically performing your calibrations and storing this information electronically. All you need to do is insert the detector into the module and press a few buttons to begin the calibration. The MicroDock II takes care of the rest!

What is Bump Testing

Bump testing a close relative to calibration. While calibration is periodic maintenance to realign a gas detector's readings, a bump test should be done daily (at least!) to verify that the sensors are actually functioning. It only takes a few seconds, and is done by applying a known concentration of the target gas to make sure that the detector goes into alarm mode when that gas reaches the sensors.

Ideally a gas detector should be bump tested at each shift change or every time it moves to a new user. At a minimum it should be done once per day. This is because a detector's sensors can fail to alarm for a wide variety of reasons:

• The sensor is at the end of its life
• The ports for the sensors have become blocked by dirt or debris
• One or more of the sensors has become damaged or 'poisoned' by any number of sources, including solvents, silicones, or overexposure to combustible gases