Company statement Re: HSE Bulletin CEMHD1 - 2020

On the 10th September, the HSE released a safety alert ‘Failure to detect dangerous gas / vapour due to incorrect specification of sample tube’ which has caused concern and raised questions for those who have received it.

The safety alert discusses an incident in which a gas monitor using a sample tube failed to detect the presence of a flammable vapour. This misleading gas detection reading led to the false conclusion that the work area was free of flammable vapour. Hot work proceeded and the subsequent explosion led to a fatal injury.

Upon investigation, it was found that the flammable vapour had been adsorbed on the inner surface of the sample tube, which meant no vapour had reached the gas monitor.

As a result, the HSE have made some recommendations that apply across the board when it comes to monitoring gases:


1) Bump test your instrument


This means that you apply a sample of the gas that the detection instrument can identify, at a known strength, and look for that result on the instrument. If you are using a sample tube when sampling live, then you should also use that sample tube when ‘bump testing’. This will enable you to ensure that the instrument is working as it should.


Using this principle will allow you to gauge the absorbency of the sample tube in use. PTFE sample tubes are commonly used for gas detection applications, but it is always worth checking against the specific gas adsorption properties (HSE research report RR635 is a paper dedicated to the phenomenon of adsorption in sample tubes).


2) Keep it short

Keep your sample tube as short as possible. This will prevent false readings being taken, which can happen when the sample takes too long to get to the instrument. The HSE have recommended in the absence of specific gas data, that an average of 3 seconds per metre should be used when dealing with sample tubes.


Here at Shawcity, we would be more than happy to speak to anyone about their current gas detection set-up and offer advice on best practice and how this HSE safety alert may affect you.


Please call our office on 01793 780622 to speak to one of our gas detection specialists.


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