Recently I was having a discussion with an end-user who was asking the question “should I be doing a bump test or a calibration check and what is the difference?”
Interesting question. By most definitions, a bump test is a brief exposure of the monitor to gas in order to verify that the sensors respond and the instrument alarms function accordingly. The bump test, by this definition, does not check the accuracy of the instrument.
This is where the calibration check comes in. A calibration check is performed by exposing the monitor to a certified concentration of gas for a particular time to verify that it provides an accurate reading.
What was confusing to this customer was that the manufacturer of his monitor was telling him to bump test and verify the accuracy of the monitor before use but was not specifying how long the gas should be applied and what the reading tolerance should be. Hmm….what should he do?
In most applications, knowing that the instrument will respond and produce an alarm that might save your life if a threatening gas hazard is encountered is all you need. In other applications, the accuracy of the reading is more important. With the instruments available today, if you are concerned about the accuracy of your readings before you use your instrument, you are better off to calibrate it rather than do a calibration check. It will generally take the same amount of time, use the same amount of gas, and will guarantee the accuracy of the instrument readings when it is completed. If you are doing a calibration check, and the readings fall outside of the desired or specified accuracy, you will have to do the calibration anyway, so you might as well do it the first time and get the guaranteed result.
In the end, it really doesn’t matter whether you choose to do the bump test, a calibration check or a full calibration. Pick the one that is right for you. The important thing is that before you take your gas monitor out and use it on a job where your life might be in danger, check it with gas in some manner.
Remember, the only way that you can be sure that your gas detector will respond to gas is to check it with gas. Do it every time!