Design and performance evaluation of a mobile CO2 detector based on mid-infrared IBBCEAS

Mobile detection and monitoring of CO2 are of extraordinary practical and scientific importance. Herein, we developed a CO2 detector for mobile monitoring platforms based on mid-infrared Incoherent Broadband CavityEnhanced Absorption Spectroscopy (IBBCEAS). The spectral transfer function and the stability calculation model for the mid-infrared broadband light source cavity were established based on the single-source dual-channel detector structure, and the calibration results showed good agreement with theoretical predictions. To meet the requirements of mobile monitoring and detection platforms, we implemented a novel design for gas intake into the chamber; the performed simulations demonstrated that the concentration equilibration time was reduced by a factor of 8.75. The optical and structural design of the detector, as well as performance evaluations conducted through relevant experiments, are given in detail. Experimental results indicated that the instrument exhibited a fluctuation of less than 9 parts per thousand under CO2 test conditions of 400 ppm (4.5 h) and 1600 ppm (4.5 h), indicating excellent stability. Allan variance calculations showed a detection limit better than 1.5 ppm with an integration time of 1 s, meeting the requirements for routine atmospheric measurements. Response time tests revealed a T50 response time of less than 3.3 s, demonstrating rapid detection of CO2 concentration changes. Field testing of the CO2 detector was conducted in an urban office park in Changchun, Jilin, China, effectively identifying variations in the local CO2 concentration along the measurement route, further confirming its potential for mobile monitoring applications.