Davenport, J. J.Hodgkinson, JaneSaffell, J. R.Tatam, Ralph P.2018-02-082018-02-082018-01-25Davenport JJ, Hodgkinson J, Saffell JR, Tatam RP. (2018) Non-dispersive ultra-violet spectroscopic detection of formaldehyde gas for indoor environments. IEEE Sensors Journal, Volume 18, issue 6, March 2018, pp. 2218-22281530-437Xhttp://dx.doi.org/10.1109/JSEN.2018.2795042https://dspace.lib.cranfield.ac.uk/handle/1826/12973We describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy. A two channel sensor was developed, making use of a strong absorption peak at 339 nm and a neighbouring region of negligible absorption at 336 nm as a reference. Using a modulated UV LED as a light source and narrow laser-line filters to select the desired spectral bands, a simple detection system was constructed specifically targeted at formaldehyde. By paying particular attention to sources of noise, a minimum detectable absorbance of 5×10 -5 AU was demonstrated with a 20 s averaging period (as ΔI/I0). The system was tested with formaldehyde finding a limit of detection of 4.3 ppm for a 195 mm gas cell. As a consequence of the low gas flow rates used in our test system, a time period of over 8 min was used in further tests, which increased the minimum detectable absorbance to 2×10 -4 AU, 17 ppm of formaldehyde. The increase was the result of thermal drift caused by unwanted temperature variation of the UV LED and the filters, resulting in a zero uncertainty estimated at 560 ppm °C -1 and 100ppm °C -1 respectively.enAttribution 3.0 Internationalhttp://creativecommons.org/licenses/by/3.0/gas detectorslight emitting diodesoptical sensorspollution measurementspectroscopyultraviolet sourcesArticle