Insights into Low-Cost Particle Sensors Using Size-Resolved Scattering Intensity of Indoor Aerosols

ALOK KUMAR THAKUR, Jonathan Gingrich, Marina Vance, Sameer Patel, Indian Institute of Technology Gandhinagar

     Abstract Number: 166
     Working Group: Indoor Aerosols

Abstract
Spatio-temporal air quality measurements, both ambient and indoor, are critical to understanding emissions sources and their profile to develop effective mitigation strategies. However, deploying multiple units of research-grade instruments to capture spatiotemporal trends can be cost-prohibitive. In recent years, cost-effective, compact, and portable low-cost air quality sensors have gained impetus for high spatial-temporal resolution measurements.

The low-cost PM sensors measure light scattering and provide an analog output (usually a voltage signal) or digital output in the form of mass concentrations based on calibrations. Low-cost sensor outputs are influenced by the particle’s physical properties, such as refractive index and size distribution. Calibrating low-cost sensors by collocating them with reference instruments is widely accepted to increase the reliability of low-cost sensor measurements. However, such calibrations are limited in terms of the type and size (or size distribution) of aerosols it can be applied to.

Different cooking experiments were performed in a test house, and the indoor PM concentration was measured using a low-cost sensor (Plantower) and reference instruments (SMPS+APS). Ultrafine particles constituted as high as 95% of total PM mass concentration during certain cooking activities. As per the manufacturer, the low-cost sensors are unsuitable for sub-300 nm PM. However, the low-cost sensor can detect cumulative scattering from high concentrations of ultrafine particles.

Firstly, correlations were checked between mass concentrations measured by the low-cost sensor and the reference instruments. Then correlations between scattering intensity (calculated using size-resolved data from the reference instruments and low-cost sensor characteristics) and mass concentration measured by low-cost sensors were checked. In addition to mass concentrations, size-resolved number concentrations reported by the low-cost sensors were also compared with that from the reference instruments. The analysis provides insights into the suitability of low-cost sensors for indoor measurements.