CO2 in Controlled-Atmosphere Storage

In a controlled-atmosphere room, O2 concentration is lowered and CO2 raised relative to ambient air, alongside strict temperature and relative humidity control. By reducing available oxygen and raising CO2, the respiration rate of the stored fruit or vegetable slows down and ripening is delayed — allowing the storage period to be extended significantly without loss of quality.

The balance is delicate: too little CO2 fails to achieve the intended effect, but an excess can cause physiological damage to the product (for example, internal browning or spotting in some apple varieties). That's why sensor accuracy and stability over the whole storage period — which can run for several months — matter as much here as in any industrial process application.

Controlled-atmosphere rooms typically operate near 0°C, with high relative humidity to prevent dehydration of the stored product. These are exactly the conditions under which many electronic sensors lose accuracy or suffer condensation on their optical components.

A probe designed for this environment needs a wide operating temperature range (including sub-zero temperatures), a housing rating suited to humidity and dust, and internal compensation for temperature, pressure and humidity so the CO2 reading stays stable throughout the whole storage cycle.

Vaisala's GMP251 probe is designed specifically for this type of environment: it measures CO2 at percentage level (0–20%), operates from -40°C to +60°C, carries an IP65 housing rating, and compensates internally for temperature, pressure, background gases and humidity. Its heated sensor head prevents the condensation typical of a cold, humid environment.

For continuous monitoring with data logging and alerts, that same reading can be integrated into a monitoring system — relevant both inside the storage room and during refrigerated transport.