Afshar-Mohajer Nima, Zuidema Christopher, Sousan Sinan, Hallett Laura, Tatum Marcus, Rule Ana M, Thomas Geb, Peters Thomas M, Koehler Kirsten
a Department of Environmental Health and Engineering , Johns Hopkins Bloomberg School of Public Health , Baltimore , Maryland.
b Department of Occupational and Environmental Health , University of Iowa , Iowa City , Iowa.
J Occup Environ Hyg. 2018 Feb;15(2):87-98. doi: 10.1080/15459624.2017.1388918.
Development of an air quality monitoring network with high spatio-temporal resolution requires installation of a large number of air pollutant monitors. However, state-of-the-art monitors are costly and may not be compatible with wireless data logging systems. In this study, low-cost electro-chemical sensors manufactured by Alphasense Ltd. for detection of CO and oxidative gases (predominantly O and NO) were evaluated. The voltages from three oxidative gas sensors and three CO sensors were recorded every 2.5 sec when exposed to controlled gas concentrations in a 0.125-m acrylic glass chamber. Electro-chemical sensors for detection of oxidative gases demonstrated sensitivity to both NO and O with similar voltages recorded when exposed to equivalent environmental concentrations of NO or O gases, when evaluated separately. There was a strong linear relationship between the recorded voltages and target concentrations of oxidative gases (R > 0.98) over a wide range of concentrations. Although a strong linear relationship was also observed for CO concentrations below 12 ppm, a saturation effect was observed wherein the voltage only changes minimally for higher CO concentrations (12-50 ppm). The nonlinear behavior of the CO sensors implied their unsuitability for environments where high CO concentrations are expected. Using a manufacturer-supplied shroud, sensors were tested at 2 different flow rates (0.25 and 0.5 Lpm) to mimic field calibration of the sensors with zero air and a span gas concentration (2 ppm NO2 or 15 ppm CO). As with all electrochemical sensors, the tested devices were subject to drift with a bias up to 20% after 9 months of continuous operation. Alphasense CO sensors were found to be a proper choice for occupational and environmental CO monitoring with maximum concentration of 12 ppm, especially due to the field-ready calibration capability. Alphasense oxidative gas sensors are usable only if it is valuable to know the sum of the NO and O concentrations.
开发具有高时空分辨率的空气质量监测网络需要安装大量空气污染物监测器。然而，最先进的监测器成本高昂，且可能与无线数据记录系统不兼容。在本研究中，对Alphasense有限公司生产的用于检测一氧化碳（CO）和氧化性气体（主要是臭氧（O₃）和二氧化氮（NO₂））的低成本电化学传感器进行了评估。当在一个0.125米的丙烯酸玻璃腔室中暴露于受控气体浓度时，每2.5秒记录一次来自三个氧化性气体传感器和三个CO传感器的电压。用于检测氧化性气体的电化学传感器对NO₂和O₃均表现出敏感性，在分别评估时，当暴露于等效环境浓度的NO₂或O₃气体时记录到相似的电压。在很宽的浓度范围内，记录的电压与氧化性气体的目标浓度之间存在很强的线性关系（R>0.98）。尽管对于低于12 ppm的CO浓度也观察到很强的线性关系，但观察到一种饱和效应，即对于较高的CO浓度（12 - 50 ppm），电压仅发生最小变化。CO传感器的非线性行为表明它们不适用于预计CO浓度较高的环境。使用制造商提供的护罩，在2种不同流速（0.25和0.5 Lpm）下对传感器进行测试，以模拟用零空气和跨度气体浓度（2 ppm NO₂或15 ppm CO）对传感器进行现场校准。与所有电化学传感器一样，经过9个月的连续运行后，测试设备出现了高达20%的偏差漂移。发现Alphasense CO传感器是职业和环境CO监测（最大浓度为12 ppm）的合适选择，特别是由于其具备现场校准能力。Alphasense氧化性气体传感器仅在了解NO₂和O₃浓度总和有价值时才可使用。
