15 May 2014 Formaldehyde sensor using non-dispersive UV spectroscopy at 340nm
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Formaldehyde is a volatile organic compound that exists as a gas at room temperature. It is hazardous to human health causing irritation of the eyes, nose and throat, headaches, limited pulmonary function and is a potential human carcinogen. Sources include incomplete combustion, numerous modern building materials and vehicle fumes. Here we describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy for the first time. A two channel system has been developed, making use of a strong absorption peak at 339nm and a neighbouring region of negligible absorption at 336nm as a reference. Using a modulated UV LED as a light source and narrowband filters to select the desired spectral bands, a simple detection system was constructed that was specifically targeted at formaldehyde. A minimum detectable absorbance of 4.5 × 10-5 AU was estimated (as ΔI/I0), corresponding to a limit of detection of approximately 6.6 ppm for a 195mm gas cell, with a response time of 20s. However, thermally-induced drift in the LED spectral output caused this to deteriorate over longer time periods to around 30 ppm or 2 × 10-4 AU.
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J. J. Davenport, J. Hodgkinson, J. R. Saffell, R. P. Tatam, "Formaldehyde sensor using non-dispersive UV spectroscopy at 340nm", Proc. SPIE 9141, Optical Sensing and Detection III, 91410K (15 May 2014); doi: 10.1117/12.2052460; https://doi.org/10.1117/12.2052460

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