With negligible global warming potential (GWP) and zero ozone depletion potential (ODP), Carbon Dioxide is considered a cost-effective, energy-efficient, natural refrigerant for food retail, food manufacturing, food processing plants, and cold chain. However, there are hazards that must be understood when using CO2 as a refrigerant; the health risks of high concentrations, higher system pressures, and the potential of dry ice formation.

Gas OEL (PPM) TWA STEL* (PPM) IDLH (PPM) LFL/UFL Alarm (PPM) Application
Carbon Dioxide (CO2) 5,000 15,000 or 30,000 40,000 N/A 5000 / 8000 Personnel Safety

* NIOSH gives a Short-Term-Exposure-Limit (STEL) of 30,000 PPM while EH40/2205HSE gives 15,000 PPM

Alarm Setpoints

Carbon dioxide monitoring instruments should be mounted in the breathing zone at approximately 5 feet from the floor. As CO2 gas is heavier than air, mounting a detector lower than the breathing zone is possible although must not be mounted above the breathing zone.

Typical CO2 gas sensors for refrigerant leak detection should be ranged from 0 to 8,000 ppm (0 – 0.8%) with specific alert and alarm set points as shown below. Actions and responses are proportionate to the detection level with the alarm notification being lower than the STEL of 15,000 ppm (1.5%) as point measurement may not specifically account for possible higher concentrations elsewhere in the room.

CO2 level Action and Response
5,000 ppm (0.5%) Alert warning notification and investigate potential leak
8,000 ppm (0.8%) Alarm warning notification, shut down valves to evaporator, initiate extraction, evacuate room

Our CO2 diffusion sensors will protect your personnel and help you comply with local regulations:

Gas OEL (PPM) TWA STEL* (PPM) IDLH (PPM) ATEL / ODL Practical Limit
R-22 1,000 1,250 59,000 0.21 kg/m3 0.3 kg/m3
R-134a 1,000 2,000 50,000 0.21 kg/m3 0.25 kg/m3
R-404A 1,000 4,000 130,000 0.52 kg/m3 0.52 kg/m3

The gas detector alarm set points, location and number of detection points outlined in the safety standards are typically insufficient for finding the more common, smaller leaks that add up to large annual refrigerant emissions, decreased efficiency and overall safety. For early warning monitoring of refrigerant leaks that provides compliance with EPA Section 608, F-Gas and CARB, gas detectors with a low minimum detection level (MDL) are required.