Sensing Technology for measuring Particle Number & Mass in Indoor Environments

Booker, Douglas and Booker, David (2019) Sensing Technology for measuring Particle Number & Mass in Indoor Environments. In: 2019 Cambridge Particle Meeting, 2019-06-28 - 2019-06-28, University of Cambridge.

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Abstract

Much has been done to quantify exposure to poor outdoor air quality. However, the conclusions drawn from these quantitative assessments have a methodological myopia: the research assumes that outdoor air quality is an accurate indicator of personal exposure. Yet, on average, people spend more than 90% of their time indoors, where levels can be significantly more polluted than outdoors. The combination of both the length of time spent inside, and the potential for higher concentrations means that personal exposure is greater indoors rather than outdoors. To address this public health knowledge gap, National Air Quality Testing Services (NAQTS) has developed an integrated indoor air quality monitor, the NAQTS V2000 to help raise awareness of indoor air quality and provide scientific data for informed public policy. The NAQTS V2000 incorporates the latest developments in low-cost sensor technologies, alongside a regulatory grade Condensation Particle Counter (CPC), thermal desorption tubes (TD), and other environmental measurements. To address “real-world” patterns of exposure and improve public health, we need a better understanding of the air quality in our indoor environments. The NAQTS V2000 unit is a portable air quality monitoring station designed to be easy-to-use for high-volume, low-cost measurements, facilitating a holistic understanding of indoor air pollution. The NAQTS V2000 measures Particle Number (CPC - d50 15nm), Particle Mass (laser-based), CO2 (NDIR), CO, NO2, and VOCs (electrochemical and metal oxide) and is also fitted with Temperature, Pressure and Relative Humidity measurements. External GPS and Noise measurements are available through USB ports on the back of the equipment. The novel integration of TD tubes for GC-MS into a real-time air pollution monitoring device allows low-cost sensors to be used as triggers for VOC speciation, adding another layer to potential analyses. This presentation will introduce the community to this new technology, and will include data insights from more than four years of development and testing, including results from a range of different indoor environments, including: Homes - Investigating the sources, concentrations, and mitigation strategies for aerosols both generated from household habits and activities, as well as from outdoor ingress. This work also investigates the dichotomy between promoting good indoor air quality & energy efficiency, as modern buildings are considered particularly problematic because of the use of more energy-efficient construction, poorly designed heating, ventilation and air conditioning, and space design. Vehicles - Despite the relatively short period of time spent in vehicles (approximately one hour per day), exposure levels are of concern given the immediate proximity to other vehicles, plus in urban areas, high ambient concentrations compared to other micro-environments. NAQTS has collaborated with Emissions Analytics Ltd to benchmark vehicles on their vehicle interior air quality, which utilises the NAQTS V2000 for simultaneous measurements of inside-outside vehicles to understand Ingress Ratio (how much ambient pollution is getting into the vehicle cabin) and Stuffiness (how well the vehicle is ventilating CO2). Schools - A socioeconomic group of particular importance are children, as they are especially susceptible to air pollution. More than just exhibiting negative health consequences, exposure to air pollution has also been associated with poor academic performance among school- aged children. The NAQTS V2000 has been used for “citizen science” activities to measure inside the classroom during school drop off/pick up times. As our concept of the health effects of exposure to air pollution aerosols moves from emission source, to air quality, to personal exposure, we must further explore our dynamic patterns of exposure in space and time, which makes our exposures in indoor environments. To address “real-world” patterns of exposure and improve public health, we need a better understanding of the air quality in our indoor environments.