scope:

INTRODUCTION

This is the third part of a four-part series of papers reporting on the test and evaluation of typical wall-mounted CO₂ sensors used in building HVAC systems. In this study, fifteen models of NDIR (non-dispersive infrared) HVAC-grade wallmounted CO₂ sensors were tested and evaluated. In all, 45 sensors (three from each model) were tested in order to determine the effects of humidity, temperature, and pressure on the CO₂ sensors' readings. The sensitivity of the sensor reading to each of these three parameters was computed and compared to the manufacturers' specifications. The experimental procedure used to test and evaluate the sensors is described in Part 1 (Shrestha and Maxwell 2009) of this paper. Among the fifteen models tested, eight models have a single-lamp, single-wavelength configuration, four models have a dual-lamp, singlewavelength configuration, and three models have a singlelamp, dual-wavelength configuration. All single-lamp, singlewavelength sensors and one single-lamp, dual-wavelength sensor incorporate an "automatic baseline adjustment" algorithm in the sensor's electronics package. The working principles of NDIR CO₂ sensors are described in Part 1 (Shrestha and Maxwell 2009) of this paper.