Use of a Dynamic Enclosure Approach to Test the Accuracy of the NDIR Sensor: Evaluation Based on the CO2 Equilibration Pattern

As part of a quality assurance (QA) study for sensor systems, an enclosureapproach is applied to assess the accuracy of non-dispersive infrared (NDIR)-based CO₂sensors. To examine the performance of the sensor system, an enclosure chambercontaining six sensor units of the two model types (B-530 and H-500) was equilibratedwith calibrated CO₂ standards at varying concentration levels. Initially, the equilibrationpattern was analyzed by CO₂-free gas (0 ppm) at varying flow rates (i.e., 100, 200, 500, and1000 mL min-1). Results of the test yielded a highly predictable and quantifiable empiricalrelationship as a function of such parameters as CO₂ concentration, flow rate, andequilibration time for the enclosure system. Hence, when the performance of the NDIR-method was evaluated at other concentrations (i.e., 500 and 1000 ppm), all the sensor unitsshowed an excellent compatibility, at least in terms of the correlation coefficients (r >0.999, p = 0.01). According to our analysis, the NDIR sensor system seems to attain anoverall accuracy near the 5% level. The relative performance of the NDIR sensor for CO₂analysis is hence comparable with (or superior to) other methods previously investigated.The overall results of this study indicate that NDIR sensors can be used to provide highlyaccurate and precise analyses of CO₂ both in absolute and relative terms.