Non-dispersive ultra-violet spectroscopic detection of formaldehyde gas for indoor environments

Date published

2018-01-25

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IEEE

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Article

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1530-437X

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Citation

Davenport 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. 2218-2228

Abstract

We 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.

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Github

Keywords

gas detectors, light emitting diodes, optical sensors, pollution measurement, spectroscopy, ultraviolet sources

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Attribution 3.0 International

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