Gas detector calibration gases

Typical calibration gas mixtures used in gas detector servicing

Example single gas detector mixes

• 5 ppm chlorine, balance nitrogen
• 10 ppm hydrogen chloride, balance nitrogen
• 10 ppm hydrogen fluoride, balance nitrogen
• 10 ppm hydrogen cyanide, balance nitrogen
• 25 ppm hydrogen sulphide, balance nitrogen
• 25 ppm sulphur dioxide, balance nitrogen
• 50 ppm ammonia, balance nitrogen
• 50 ppm nitric oxide, balance nitrogen
• 100 ppm carbon monoxide, balance nitrogen
• 1% carbon dioxide, balance nitrogen
• 2% hydrogen, balance nitrogen
• 2.5% methane, balance nitrogen

The last two items in this list represent 50% of the LEL for the respective flammable components.

It is also common that most of the above mixtures are supplied in a balance of air instead of nitrogen. Nitric oxide is an exception and it can only be supplied in a nitrogen balance due to its reactivity with air to produce nitrogen dioxide. 

Common quad gas mix variants

• 2.5% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, 18% oxygen, balance nitrogen
• 1.25% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, 18% oxygen, balance nitrogen
• 2.5% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, 21% oxygen, balance nitrogen
• 1.25% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, 21% oxygen, balance nitrogen

The last two mixes in this list are also known as:

• 2.5% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, balance air
• 1.25% methane, 25 ppm hydrogen sulphide, 100 ppm carbon monoxide, balance air

Quality levels for gas detector gas mixtures

The quality requirements for daily use functional test gas mixtures (bump test gases) are generally not as high as the gas mixtures used for the detector and sensor calibration. For the functional test gases, a general certificate of analysis is often appropriate. Alternatively, a higher quality ISO/IEC 17025 accredited gas mixture might be specified.

For the quarterly, half yearly or annual calibration of gas detector sensors, it is often required to use an ISO/IEC 17025-accredited calibration gas mixture. For the highest levels of measurement confidence and traceability, it would be necessary to use the higher quality classification of an ISO 17034-accredited reference material calibration gas mixture.

It should be noted that under the correct usage and interpretation of the ISO 17034 standard for reference material producers, each individual cylinder must be prepared and validated for stability and homogeneity. It is therefore not possible to decant-fill ISO 17034 reference materials from a large mother cylinder to smaller portable cylinders and declare the smaller cylinders as also being ISO 17034 compatible, unless they are subsequently also individually analysed, which would consume a high proportion of their contents. It is therefore not feasible.

World class capability

We are proud to be a world class manufacturer of certified reference materials for gas detector calibration. Our NATA accreditation for multiple component reactive gas mixtures is highly valued in Australia and worldwide. We are also proud to export these products to locations as far away as South America.

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