sensivity spectrum 1

Infrared (NDIR) vs Metal Oxide Semiconductor Sensors (MOS)

When using a Variable refrigerant flow (VRF) system in an enclosed space, there is a risk of the charge leaking into rooms. Depending on the refrigerant type and charge, this can lead to asphyxiation via oxygen depletion as well as dizziness, headache, and confusion from toxic gases. Early warning without false alarms are essential for safety of people utilising the rooms.

When using a detector consideration must be given to not only the price but the cross-sensitivity and amount of false alarms that it has the possibility of creating. Other items to be considered are the accuracy, reliability, maintenance requirements and expected life span. The other items to take into account when selecting a VRF system unit is the aesthetic look and also the other items that may be used in the room such as Volatile Organic Compounds from items such as cleaning agents, aerosols and item like nail polish.

The Infrared sensors are less likely to be affected by items like humidity and temperature changes. Due to the fact that metal oxide sensors have a “Broad” sensitivity they cannot see just one gas but multiple which lends itself to false alarms along with the required high temperature that they need to see the gas.

The NDIR sensor does not have the problem of cros- sensitivity and reactions to humidity and temperature, it also does not age as quickly as its MOS counterpart. Poisoning is also something that will not happen when using the NDIR version as the gas does not come into contact with any active part of the sensing stream.

In conclusion, the NDIR sensor will work for longer and be more accurate with less false alarms, which will bring your overall cost down due to servicing costs and call outs due to the false alarms. The most reliable and cost-effective solution is the NDIR sensor.

Rob Whittet | General Manager, Gas Detection Australia.

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