How do you select a calibration gas?

By Milan Boer on Mar 19 in Blog.

There are many different types of calibration gas available for the calibration of various types of gas detectors with each their specific sensor type or sensor configuration. First, you have to determine what kind of gas detector needs to be calibrated. Gas detectors can be single gas detectors or multi-gas detectors.

What calibration gas needs a single gas detector?

A single gas detector should be calibrated with a single gas which could be a flammable gas, oxygen or toxic gas. The single gas used for calibration of the single gas detector is not necessarily brand related. A single flammable gas detector needs to be calibrated with a single flammable gas which is methane calibration gas or iso-butane calibration gas in most of the times. A single gas oxygen detector could be calibrated with pure nitrogen calibration gas or with oxygen calibration gas. A toxic single gas detector needs to be calibrated with a specific single toxic gas which depends on what toxic gas type the single toxic gas detector is designed for. For example, a single gas CO detector needs calibration with carbon monoxide calibration gases, and a single gas H2S detector needs calibration with hydrogen sulfide calibration gases. There are many specific toxic single gas detectors which each requires their own particular toxic calibration gases for calibration.

What calibration gas needs a multi-gas detector?

Multi-gas detectors are calibrated with calibration gases mixture which are brand related. Every brand multi-gas detector needs calibration with its own specific gas mixture. This has resulted in the fact that there are specific calibration gas mixtures for multi-gas detectors of brands Riken Keiki, MSA, Dräger, Crowcon, GMI, BW Technologies, RAE, etc. These calibration gas mixtures are most of the times 4-gas mixtures including carbon monoxide, hydrogen sulfide, flammable gas and oxygen in balance nitrogen. The flammable gas type in the various gas mixtures is most of the times methane or iso-butane and sometimes propane. The flammable gas concentration of each specific flammable gas is always a %Vol which is equal to 50%LEL. Where gas mixes of different brands differ from each other are the height of the ppm concentrations of toxic gases such as carbon monoxide and hydrogen sulfide and the height of the %Vol concentration of oxygen.

What cylinder size is required?

Disposable calibration gas cylinders are available in 10, 34, 58 and 110 litres. Single gases are available in all four-cylinder sizes. Gas mixtures are only available in volumes of 34, 58 and 110 litres. Which cylinder size should be used is in principle free to choose. The larger the cylinder size, the more content, the more expensive the price.

Does my calibration gas need a manual regulator or an on-demand flow regulator?

Diffusion type gas detectors (without suction pump) need calibration gases with a manual regulator. With a manual regulator, the flow rate of the calibration gases that is led to the gas detector should be regulated manually. Pumped type gas detectors (with internal suction pump) need calibration gas with an on-demand flow regulator. With an on-demand flow regulator, the flow rate of the calibration gas that is led to the gas detector is regulated full automatically with the internal pump of the gas detector. Manual regulators are available for cylinder sizes 10, 34, 58 and 110 litres. On-demand flow regulators are available for cylinder sizes 34, 58 and 110 litres.

 

 

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