Rapid Detection of CO2 in Cooling & Refrigeration


Refrigeration is used throughout industry wherever there is a need to maintain a product or process at a defined temperature level. Compressing a refrigerant gas then allowing it to evaporate provides this cooling process. Several gases can be used to perform this action, natural gases such as Ammonia and Carbon Dioxide or manufactured range of gases known as Freons. For many years Freons (CFC’s, HCFC’s) were seen as ideal clean, non-toxic, odourless etc., however, it was discovered that CFC’s cause depletion of the ozone layer and were therefore banned. Their replacements, while causing less harm to the ozone layer, have a high global warming potential, in some cases 100 times that of CO2. These gases are controlled by legislation known as F-Gas regulations, placing strict limits on the use of these gases and the necessity to detect them.

Carbon Dioxide is gaining increased popularity in the refrigerant industry particularly for use in cooling computer cores and rooms. The benefits of CO2 for these applications are that it is clean, odourless and inexpensive.

The drawback of CO2 is that its use in refrigerant systems requires that it needs to be compressed to much higher pressures than either Freons or Ammonia. While CO2 is not covered by the F-Gas regulations, it is certainly subject to DSEAR regulations. The main thrust of the DSEAR regulations is to control the use of dangerous substances and gases in the workplace. CO2 is an asphyxiate and can cause both drowsiness and headaches and therefore must be monitored. An additional problem is that, because of the higher pressures involved, any leak of CO2 can quickly cause the loss of all of the refrigerant system gas. Therefore, quick speed of response is imperative to allow the system to close valves and prevent this loss.

Typically, alarm levels are set at 0.5% V/V and 1.5% V/V. Sensors should always be placed as close to ground level as possible where CO2 will build up in the event of a leak. CO2 can be considered to act like water in its flow characteristics and this should be taken into consideration when positioning the sensors.

Typical market segments include:

  • IT
  • Banking and Finance
  • Food Industry (where Ammonia might taint food)
  • Abattoirs
  • Pharmaceuticals


The larger traditional refrigerant leak detection systems are often based on extractive, sample system type products (known as sniffer systems). This is where sample lines are placed at possible leak points and samples are sequentially drawn through the system and passed across a suitable sensor. These systems have the disadvantage that they can take several minutes before all the sample lines are sequenced. This results in a leak possibly going undetected for up to half an hour. Excessive in the case of CO2.

Therefore, an effective system for this application should be able to detect a leak in the refrigerant gas in less than 30 seconds.


GMI have a wide range of products specifically designed to meet and exceed all requirements of gas detection in the refrigeration industry. These systems have been designed to meet the vast range of different applications that are presented by using CO2 as a refrigerant gas. The Active-8 and Active-80 control systems can be wired to low cost Infrared CO2 detectors installed at all potential leak sites.

The Active-8 and Active-80 control systems will have programmable alarm set points normally set at 0.5% v/v and 1.5% v/v and will provide either volt free contacts or 4-20 mA outputs to the refrigerant control system to allow shut down valves to be activated. These systems can achieve response times better than 10 seconds in the right circumstances.

Users of GMI Carbon Dioxide systems include:

  • Glaxo Smith Kline
  • Scottish and Newcastle
  • Coors
  • British Energy
  • De-Montford University
  • Leicester City Council
  • Plus many others

GMI are more than happy to discuss your particular requirement for detection and will be able to propose the best system for your needs. This service is provided free of charge and without any obligation, so please call GMI +44 (0) 141 812 3211 and ask for Fixed Systems Applications Team or alternatively, e-mail our sales team.

As an ISO 9001 approved company, GMI Ltd’s quality assurance programmes demand the continuous assessment and improvement of all GMI products. Information in this article could thus change without notification and does not constitute a product specification.

Please contact GMI or their representative if you require more details.