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Efficacy of Paired Electrochemical Sensors for Measuring Ozone Concentrations
Typical low-cost electrochemical sensors for ozone (O 3 ) are also highly responsive to nitrogen dioxide (NO 2 ). Consequently, a single sensor's response to O 3 is indistinguishable from its response to NO 2 . Recently, a method for quantifying O 3 concentrations became commercially available...
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| Published in: | Journal of occupational and environmental hygiene 2019-02, Vol.16 (2), p.179-190 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Typical low-cost electrochemical sensors for ozone (O
3
) are also highly responsive to nitrogen dioxide (NO
2
). Consequently, a single sensor's response to O
3
is indistinguishable from its response to NO
2
. Recently, a method for quantifying O
3
concentrations became commercially available (Alphasense Ltd., Essex, UK): collocating a pair of sensors, a typical oxidative gas sensor that responds to both O
3
and NO
2
(model OX-B431) and a second similar sensor that filters O
3
and responds only to NO
2
(model NO2-B43F). By pairing the two sensors, O
3
concentrations can be calculated. We calibrated samples of three NO2-B43F sensors and three OX-B431 sensors with NO
2
and O
3
exclusively and conducted mixture experiments over a range of 0-1.0 ppm NO
2
and 0-125 ppb O
3
to evaluate the ability of the paired sensors to quantify NO
2
and O
3
concentrations in mixture. Although the slopes of the response among our samples of three sensors of each type varied by as much as 37%, the individual response of the NO2-B43F sensors to NO
2
and OX-B431 sensors to NO
2
and O
3
were highly linear over the concentrations studied (R
2
≥ 0.99). The NO2-B43F sensors responded minimally to O
3
gas with statistically non-significant slopes of response. In mixtures of NO
2
and O
3
, quantification of NO
2
was generally accurate with overestimates up to 29%, compared to O
3
, which was generally underestimated by as much as 187%. We observed changes in sensor baseline over 4 days of experiments equivalent to 34 ppb O
3
, prompting an alternate method of calculating concentrations by baseline-correcting sensor signal. The baseline-correction method resulted in underestimates of NO
2
up to 44% and decreases in the underestimation of O
3
up to 107% for O
3
. Both methods for calculating gas concentrations progressively underestimated O
3
concentrations as the ratio of NO
2
signal to O
3
signal increased. Our results suggest that paired NO2-B43F and OX-B431 sensors permit quantification of NO
2
and O
3
in mixture, but that O
3
concentration estimates are less accurate and precise than those for NO
2
. |
|---|---|
| ISSN: | 1545-9624 1545-9632 |
| DOI: | 10.1080/15459624.2018.1540872 |