How often should you change gas detector sensors?

Ask John, our gas detection expert

I have frequently been asked: “How often should you change gas detector sensors?” The answer to this question is really quite simple.

There is really no recommended maintenance schedule for replacing the sensors in a portable gas detector.

You should not look at the sensors like changing the oil in your car, but more like filling the gas tank. When the sensors don’t have enough sensitivity to calibrate successfully, they are essentially out of gas and should be replaced. As long as there is still “gas in the tank” the sensors are okay for use.

Industrial Scientific instruments have a standard methodology for reading the sensor gas gauge and determining how much is left in the tank. It is called the full span value or span reserve value.

The span reserve value is the measure of sensitivity in the sensor determined during a calibration. It is displayed on the gas detector for each sensor at the end of calibration and is stored in the instrument calibration records.

Sensors with a span reserve value less than or equal to 50% of the calibration gas concentration are out of gas. They will fail calibration and must be replaced.

The “low fuel light” will come on when the span reserve value is between 50% and 70% of the calibration gas concentration. This indicates that the sensitivity is marginal and you should consider refuelling your gas detector by replacing the sensors before the tank is completely empty.

How often should you change gas detector sensors?

So the bottom line is this. As long as your sensors have enough sensitivity or span reserve to calibrate successfully they are good to go.

There is no need to change the sensors until they fail calibration and can no longer be used. Keep your eye on the gas gauge – the span reserve value – and you won’t be caught with no gas in your sensor’s tank.


  1. Gary Harris says

    Can someone please contact me regarding the purchase of 4 portable gas detectors please.