A new laser-based and ultra-portable gas sensor for indoor and outdoor formaldehyde (HCHO) monitoring

Abstract

n this work, a new commercially available, laser-based, and ultra-portable formaldehyde (HCHO) gas sensor is characterized, and its usefulness for monitoring HCHO mixing ratios in both indoor and outdoor environments is assessed. Stepped calibrations and intercomparison with well-established laser-induced fluorescence (LIF) instrumentation allow a performance evaluation of the absorption-based, mid-infrared HCHO sensor from Aeris Technologies, Inc. The Aeris sensor displays linear behavior (R2 > 0.940) when compared with LIF instruments from Harvard and NASA Goddard. A nonlinear least-squares fitting algorithm developed independently of the sensor's manufacturer to fit the sensor's raw absorption data during post-processing further improves instrument performance. The 3σ limit of detection (LOD) for 2, 15, and 60 min integration times are 2190, 690, and 420 pptv HCHO, respectively, for mixing ratios reported in real time, though the LOD improves to 1800, 570, and 300 pptv HCHO, respectively, during post-processing. Moreover, the accuracy of the sensor was found to be ± (10 % + 0.3) ppbv when compared against LIF instrumentation sampling ambient air. The aforementioned precision and level of accuracy are sufficient for most HCHO levels measured in indoor and outdoor environments. While the compact Aeris sensor is currently not a replacement for the most sensitive research-grade instrumentation available, its usefulness for monitoring HCHO is clearly demonstrated.