SUMMARY: An automatic continuous‐flow sampling system for monitoring respiratory gas was developed. Continuous airflow at constant pressure and temperature was pumped through 24 chambers. The airflow was regulated by needle valves connected to 3‐way solenoids which sequentially switched the sample to a CO2 infrared analyzer and recorder. A timing cycle was selected so that each sample was analyzed every 3 hr. The recorder was calibrated to read directly in percent CO2. Results were expressed as ml CO2/kg product/hr. The system was used to determine the respiratory activity of irradiated and nonirradiated citrus fruits. Irradiated fruits exhibited marked increases in CO2 production reaching a maximum 1‐2 days after treatment then gradually declining. Waxing limited the production of CO2 especially with irradiated fruits. All fruits were treated with sulfanilamide to prevent post irradiation infection by mold.