The influence of humidity on the performance of a low-cost air particle mass sensor and the effect of atmospheric fog

Rohan Jayaratne,Lidia Morawska,Xiaoting Liu,Matthew Dunbabin,Phong Thai

doi:10.5194/amt-11-4883-2018

Abstract

Abstract. While low-cost particle sensors are increasingly being used in numerous applications, most of them have no heater or dryer at the inlet to remove water from the sample before measurement. Deliquescent growth of particles and the formation of fog droplets in the atmosphere can lead to significant increases in particle number concentration (PNC) and mass concentrations reported by such sensors. We carried out a detailed study using a Plantower PMS1003 low-cost particle sensor, both in the laboratory and under actual ambient field conditions, to investigate its response to increasing humidity and the presence of fog in the air. We found significant increases in particle number and mass concentrations at relative humidity above about 75 %. During a period of fog, the total PNC increased by 28 %, while the PNC larger than 2.5 µm increased by over 50 %. The PM10 concentration reported by the PMS1003 was 46 % greater than that on the standard monitor with a charcoal dryer at the inlet. While there is a causal link between particle pollution and adverse health effects, the presence of water on the particles is not harmful to humans. Therefore, air quality standards for particles are specifically limited to solid particles and standard particle monitoring instruments are fitted with a heater or dryer at the inlet to remove all liquid material from the sample before the concentrations are measured. This study shows that it is important to understand that the results provided by low-cost particle sensors, such as the PMS1003, cannot be used to ascertain if air quality standards are being met.

Highlights

The rapid technological advancements in the fields of material science, digital electronics, and wireless communication have given rise to a wide range of low-cost air quality sensors that are readily available on the market
As the humidity in the chamber was gradually increased, the particle mass concentrations reported by the PMS1003 did not show a significant change until the relative humidity reached about 78 %
The PM2.5 readings indicated by the PMS1003 increased steadily from about 9 μg m−3 at a relative humidity of 78 % to about 16 μg m−3 at the maximum relative humidity of 89 % achieved in this experiment, an increase of almost 80 %

Summary

Introduction

The rapid technological advancements in the fields of material science, digital electronics, and wireless communication have given rise to a wide range of low-cost air quality sensors that are readily available on the market. These sensors are increasingly being used in many applications that were previously not achievable with conventional expensive equipment (Kumar et al, 2015; Rai et al, 2017; Snyder et al, 2013). Single gas sensors are very often affected by other interfering gases (Fine et al, 2010; Piedrahita et al, 2014), while environmental parameters, such as temperature and humidity, can affect the performance of these sensors under cer-

Methods

Results

Conclusion