From the 1st November 2010, EN60079-29 part 1 has been harmonised under the ATEX directive 94/9/EC. Therefore to comply with the ATEX directive, portable apparatus sensing flammable gases should have a functional check with gas before each day of use.
“I have just had my gas monitor calibrated, therefore it will continue to detect gas until the next calibration!”
Whilst a monitor can initially pass the start-up process and indicate that the monitor is functional, what this doesn’t tell you is if gas can actually reach the sensor, as the sensor membranes can become clogged with muck, dust and particles that are not visible to the human eye and thus not allowing the gas molecules to reach the sensor and react in a timely fashion.
A bump test is the only way to test that 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 and it confirms that all the alarms are activated and the detector goes alarm properly.
The principle behind bump testing remains the same across all manufacturers, with a target gas applied to the monitor for usually around 30-40 seconds with a flow rate of around 0.5lpm, this exposes the sensors to the target gas and the monitor (depending on manufacturer) will show gas readings and alarms should respond accordingly. You would normally expect to see readings within 10% of the target gas applied.
“How often should I bump test my gas monitor?”
Taking into consideration the ATEX directive, manufacturer recommendations and your own company risk assessments, it is recommended that you bump test your monitor before every use, it is true that the law is not clear and doesn’t use the all-important word “MUST” and the regulation only surrounds flammable gases, not toxic, but you can guarantee that the authorities would want to see evidence of such testing should the worst happen!
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