Calibration of gas detectors is vital to be sure that they are in good working order and able to alert the user to gas hazards in their vicinity. A calibration is a “resetting” of the detector’s response against a known concentration of target gas, in a balance of synthetic air or nitrogen. This will determine the relationship between the detector’s reading and the actual concentration of the component gas of interest. Adjustment involves modification of the detectors response to bring the reading into line with what is expected while exposing the instrument to the known source. This is fundamentally different to bump testing which is a brief exposure to gas in order to verify that the sensors respond within a specific boundary and the detector’s alarms function properly.
Gas detection is a critical safety function in many industries, to protect people from harm and avoid costly plant disruption or damage. Not only must you use a suitable instrument for the task and the environment, but it must be used correctly and maintained properly if it is to fully serve its purpose.
Gas detectors are there to save your life, whether it is a fixed system or a portable detector, keeping them well maintained is an important part of ownership.
Our guest blogger this week, Julian, has put together simple steps to ensure your gas detector is up for the job as and when it’s required.
The nature of gas hazards posed by some working environments can be complex and complete protection is not available from a single solution. This week, our guest blogger, Richard, takes a look at VOCs: how they pose a hazard and what we can do to protect against them.
After last week’s comparative levity, this week, I am discussing something rather more serious.
When it comes to detecting hydrocarbons, we often don’t have a cylinder of target gas available to perform a straight calibration, so we use a surrogate gas and cross calibrate. This is a problem because pellistor’s give relative responses to different flammable gases at different levels. Hence, with a small molecule gas like methane a pellistor is more sensitive and gives a higher reading than a heavy hydrocarbon like kerosene.
A common question we encounter at Crowcon is when to use a pump or aspirator with a portable gas detection device. I’d like to share some thoughts about the use of personal detectors with pumps or aspirators as part of an effective confined space pre-entry check.
I’ve talked about bump testing your instrument, so it seems natural that we now cover the importance of calibrating.
There are two main reasons for calibration. Firstly, gas detectors often operate in harsh environments: high and low temperatures and/or humidities; they may be exposed to contaminants, such as solvents, silicone etc; gas exposure; as well as the age of a sensor; any of which can result in the degree to which the detector responds to a given gas concentration changing, for example, the detector may read 46% LEL when the true level is 50% LEL.
Following on from last week’s article, ‘Why do I need to bump test my instrument?’, I thought I’d give you a little more detailed information about what is a bump test and how to carry one out.
Crowcon’s expert, Chris is here to answer your question
There are lots of reasons why a portable gas detector may not react to gas, some of which may not be obvious when you pick up a unit. The safest way to make sure your gas monitor is working is to ‘bump’ test it.
