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What is a Calibration Gas Used For?

To understand the importance of a calibration gas we must first understand the dangers of toxic, flammable, and oxygen depleted atmospheres.

There are sadly many ways in which an enclosed atmosphere can become lethal, this could be through a build-up of a toxic gas. Hydrogen sulphide (H2S) for instance, caused by decomposition of organic matter, is a hazard in the oil and gas industry, and the build-up of this dangerous gas can rapidly make an atmosphere deadly. Another example is aboard a cargo ship. It is quite possible for organic goods - such as timber - to produce high levels of carbon dioxide (CO2) through organic reduction, resulting in an oxygen depleted atmosphere. In a recent incident two crewman on a cargo ship lost their lives after the hold containing the logs was found to have oxygen levels as low as one percent. This was unknown to the first crewman who upon entering the hold immediately passed out and fell from the entrance ladder, or the second crewman who rushed in to save him.

In this tragic example gas detectors and following correct procedures could have saved both lives, as they allow workers to safely operate in potentially dangerous settings. A gas detector will alert the user when a toxic gas in encountered, or alarm when oxygen saturation drops below 19 percent, at which point adverse effects will be noticeable. Gas detectors are without doubt life saving devices, so long as they are working correctly, and this is where calibration gases come in.

There are two types of functional tests that you can carry out on a gas detector, these are known as a bump test and a calibration. A calibration gas is required for both tests and is simply a very accurately measured gas mixture, this could be a small quantity of a toxic gas, such as 100ppm of carbon monoxide, a level at which you would want to be alerted to avoid injury. Another example would be 18 percent oxygen in a nitrogen balance gas, or the level at which you would want a gas detector to warn you of a present danger.

All calibration gases contain a balance gas, typically this will be an inert gas which makes up the balance of the finished product above the appropriate level of the active gas. Balance gases should be inert, so they won't trigger the gas detector, and are typically nitrogen or artificial air.

In a bump test, the calibration gas is introduced to the gas detector.  The alarm on the gas detector should then sound to alert the user that it is functioning correctly. A bump test is a quick and easy test and should be performed before every use of a gas detector.

A calibration is something that should be carried out less frequently, perhaps once a month or less depending on your protocols.  Here, the intention is not just to check that the gas detector is functioning, but that it is accurately measuring the gas levels, it is then possible to adjust the settings on the detector for future readings.

So, you can see that the calibration gas is just as important as the gas detector itself, as without it you can't be sure that the detector is functioning or accurately measuring gas levels. Luckily, it is easy to source calibration gas cylinders, as Air Products offers the ability to purchase online with courier shipping, meaning that you can be up and running in no time. Visit airproducts.expert/uk/oneuse to browse the range of off-the-shelf calibration gases, in lightweight portable aluminium canisters.


"Our business relies on simple bump testing of gas detectorson board marine vessels. Complex high pressure cylinders and regulators would make the job too difficult but we find the Air Products non-refillable offerings very easy to use and the equipment is simple to operate."

GMS Instruments, Rotterdam

"We are involved in the installation, commissioning and maintenance of a wide range of gas detection equipment into many market sectors. The fact that the Air Products’ range covers all of the flammable, toxic, quad-gas and corrosive gas requirements for this market is very important to us."

Autochim, France

"Personal, portable and fixed gas detection equipment is widely used in many safety critical applications and these items are often subjected to relatively harsh environments and working conditions. The gas sensing element within this equipment is perhaps the most fragile and crucial component, and if this was to fail, it would render the equipment useless. The selection of appropriate test gas is important to ensure the bump test is carried out correctly and as an active member of CoGDEM, Air Products know about it. They have contributed to the CoGDEM Guide to Gas Detection, a new hardback reference book which explains best practice and aids the selection of suitable test gases and equipment."

Leigh Greenham, Director, CoGDEM

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