How is gas detected using the gas detector tube system?

The detector tubes are generally supplied in packs of ten, and are sealed at both ends. In operation, the tips are broken off using a tube tip breaker, a neat function often within the hand pump or otherwise sold as a separate item. Gas detector tubes are used with a handheld air sampling pump.

Depending on the manufacturer, the pump utilises either a bellows or piston design. The pump connects to one end of the detector tube and the user draws a sample of 50ml or 100ml of ambient air.

As the gas sample works its way up the tube towards the sampling pump, it reacts with the chemical reagent within the tube. The colour stain produced is proportional in length to the concentration. By using a calibration scale printed on the tube, the concentration may be read immediately, without the need for laboratory analysis. The point where this reaction stops is easily read off against markings on the gas detector tube.

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