What is a bump test?
A bump test is a routine that involves passing a known gas charge over the cells of a gas detector to check that they are operating correctly.
By passing the gas, the device checks the detector's alarm functions by creating a situation of gas presence.
This function test is only for checking purposes and does not alter, in any way, the device measurement accuracy.
The origin of the functional test
Before the introduction of confined-space standards, portable gas detectors featured analog needles or LED displays. These systems were initially used to downgrade zones during maintenance operations or to detect high concentrations of explosive gases or oxygen-deficient atmospheres in mines. The quality of these devices led manufacturers to recommend calibration daily to check their proper operation and accuracy.
The worldwide deployment of portable gas detectors has been significant since the confined space regulations introduced in 1993 in the USA and 1997 in the UK. But daily calibration was becoming a big economic burden. Industries then asked manufacturers to find a solution to simplify their day-to-day work. Therefore, they came up with the gas test for detectors. It was a quick and easy way of checking the proper operation of the device before use. The term "bump test" or "functional test" has entered the vocabulary of portable gas detector manufacturers and users alike.
Why is a functional test for gas detectors essential?
The environment in which the device is used will determine how well it operates. In fact, gas detectors are subject to numerous parameters that can clog the filter on the detection cells, such as ambient humidity and dust. They are generally used in harsh conditions and are subject to shocks and damage not always visible to the naked eye. Functional testing remains the easiest and safest way of checking if a detector works correctly.
How to perform functional tests?
There are two ways to perform these function tests. The first is to do it handly by connecting a standard gas cylinder via a calibration cap to the detector. Then, enter the menu and follow the instructions indicated on the instrument and the instruction manual to perform the operation. This is not the easiest procedure, and it is not used often.
To facilitate these tests, manufacturers have developed automatic stations (Docking Stations) that perform these tests according to the frequency defined by the company's internal policies. These stations prevent operators from wasting too much time carrying out this operation and require no training. Place simply the detector on the station. The station will then tell the operator whether the test has passed or failed.
What are the risks of not performing a bump test?
Relying on the iNet solution, Industrial Scientific carried out numerous studies and analyses to determine the reliability of the bump tests. To do this, they took 1 billion concentration data records, 4.7 million functional test records, 1.1 million calibrations, and 2.5 million alarms. The results were surprising: the failure rate of a daily bump test is 0.3%, or three detectors out of every 1,000. By spacing out the bump test frequency to 20 days, the failure rate is multiplied by 2.