How to prevent false ammonia alarms

Ammonia (R717) detection systems are needed in all ammonia refrigeration systems to minimise the effects of accidental releases of the refrigerant. However, false alarms, if they happen too frequently, can undermine the effectiveness of the detection system. 

Addressing this issue, Calibration Technologies, Inc. (CTI) has published a white paper on how to prevent false alarms (To access the paper, click on the button below.) 

The paper addresses the seven main reasons for false alarms:

1. The detector is not matched for the environment and detection range. It is important to choose the best fitting sensor for your individual application. 

2. The sensor detects a gas that is not ammonia. Not every sensor exclusively measures the concentration of ammonia. Consult an engineer of your choice about gases with cross-sensitivities, which are mainly carbon monoxide, hydrogen sulphide or cleaning materials.

3. Moisture and condensation can be a special challenge for sensors. The extreme and rapid changes in humidity in the food industry can cause peaks in the signals, leading to a false alarm. For this, the authors recommend special sensors. 

4. Rapid and big fluctuations in temperature have a similar effect as condensation on the detection system. This also influences the humidity in the air, amplifying the danger of false alarms. For this, the authors also recommend special sensors. 

5. Sensors can be damaged by water and other cleaning chemicals. It is good practice to protect all sensors that are likely to be sprayed directly with water. A shield and an enclosure can help to protect the sensor.  

6. Sensors need to have a well-set alarm range. As a rule of thumb, you should set the point at approximately 10% of the full scale of the detector (e.g., with a set point of 25 ppm, the detector should have a full scale of no more than 0-250 ppm). Know your set points before purchasing the detector. 

7. Sensors can react to electrical interference. To solve this problem, avoid having the sensor cables in the same conduit as AC electrical cables. Also, keep the sensor and its wires away from mercury vapor lights, variable speed drives and radio repeaters.