• To warn if the amount of harmful CFCs (environmentally and ecologically) reaches an unhealthy level.

• To minimize the emission of expensive freon gases

Freon is a heavy and suffocating gas which in case of combustion can cause the formation of the highly toxic gas phosgene. Since the gas does not warn you of its presence through its smell it is advisable to monitor the gas as a safety precaution.

According to norms, cold stores containing more than 25 kg of Freon must be equipped with a gas monotoring system. In cases of system fillings, other relevant areas must also be monitored.

When considering freon from a monitoring point of view, it is appropriate to have two alarm levels, where the first gives an alarm at around 300-500ppm and the second at about 500-1500ppm. The recommendation differs from the hygienic threshold levels.

If you require a higher sensitivity, alert level 1 can be set at a lower level so that the plant gives an alarm for very small leakages. In this way, the gas monitoring facility can save on the very expensive freon.

The recommendation is a sensor density of about 1 sensor/100m² or more if a higher leakage warning capability is required.

In some cases, you can supplement these facilities with an asphyxia warning system. Since the hygienic limits for hazardous atmosphere is much lower for freon, this measuring method is normally sufficient.

Ventilation control
The ventilation in the cold stores is generally temperature controlled since refrigeration compressors produce a great deal of heat.

This means that fans in cold stores run at full speed during summer.

Irrespective of how the ventilation control system is solved, it is important to "override" the temperature control so that at level 1 the fans at least run at half speed and at level 2 at the 1/1 power alternative, analog with a frequency converter.

The instrument should be located so that the alarm and any readings can be easily read. It should also be located in a frequented and meaningful place (outside the cold store).

To manage the monitoring- and control data, the instrument should have two alarm levels (with associated relays) and concentration readings.