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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 8 | Copyright
Atmos. Meas. Tech., 11, 4883-4890, 2018
https://doi.org/10.5194/amt-11-4883-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 27 Aug 2018

Research article | 27 Aug 2018

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

Rohan Jayaratne1, Xiaoting Liu1, Phong Thai1, Matthew Dunbabin2, and Lidia Morawska1 Rohan Jayaratne et al.
  • 1International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, QLD 4001, Australia
  • 2Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia

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 2.5µm 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.

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It is important to correctly interpret the readings reported by low cost airborne particle sensors at high humidity. We demonstrate that deliquescent growth of particles and the formation of fog droplets in the atmosphere can lead to significant increases in particle number and mass concentrations reported by such sensors, unless they are fitted with dryers at the inlet. This is important as air quality standards for particles are specifically limited to solid particles.
It is important to correctly interpret the readings reported by low cost airborne particle...
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