There are many reasons why a portable gas detector may not react to gas, some of which are not visibly evident to the user. When an instrument is turned on, you can see that the battery and display are working properly, but what about the internal electronics which play a critical role in protection? Do the sensors and alarms all work, have they been inhibited by using the wrong cleaning solution or have their openings become obstructed by mud? How do you know?
A bump test is the only way to ensure the whole gas detector unit is working properly. It checks that the sensors respond to the target gas, it also verifies that the display reacts. It confirms that all the alarms are activated, and the detector goes properly into alarm.
How does it work?
The aim of the bump test is to make sure a gas monitor is working at its optimum by briefly exposing the unit to a known concentration of the target gas. The reading is compared to the actual quantity of gas present, as stated on the test gas cylinder, and if the detector goes into alarm within an acceptable range of the actual concentration, usually within 10%, then it is working safely. If the bump test results are not within the acceptable range, or it takes more than 30-40 seconds to alarm, the gas detector must not be used until a full calibration has been conducted.
So why are people still not bump testing regularly?
The list of reasons is always the same:
- It takes too long
- It’s too hard and takes training
- There’s no law saying we have to
However, the average time to bump test is 20-30 seconds – less time than it takes to put on the rest of PPE! Depending on the detector used, there may be semi-automated or automated systems available to perform the bump test, so making the procedure very simple. The best of these can be configured so that the detector only has to be inserted, and it does the rest, from applying the gas to recording the results for compliance purposes. Little to no training is required, though this does not remove the need for training on why it is necessary!
The manufacturer’s recommendation will suggest a frequency for testing, although how frequently the unit is used can also be relevant. The user should perform a risk assessment with regard to how often they bump test to ensure they keep their operators safe and bear in mind the ATEX recommendations. True, the laws are not clear, but they are written in such a manner to make bump/function testing a requirement. After all, if something does go wrong, what would justify not bump testing to the authorities?
Please remember, however frequently you bump test, this does not remove the need to have gas detectors inspected, calibrated and serviced periodically by a competent individual.