| Keywords |
low cost sensor; light scattering; particulate matter; humidity; liner regression |
| Abstract |
Inaccuracy of particulate matter from light scattering sensors has been reported, where the environmental parameters including aerosol size, physiochemical properties, temperature and relative humidity play important roles in the accuracy of measurements. We explored the effect of relative humidity using six light-scattering devices in environmental chamber. Potassium chloride aerosol was exposed to the chamber, and the devices including tree firstclass certified, two out of class, and one dehumidification device, were applied to measure particulate matter. The confidence interval of the data was monitored based on RPj, which is a precision index used in EPA's field sampling procedure and the criteria of the interval is 7%. In both the low-humidity and high-humidity experiments, the measurements from first-class devices were problematic compared to the other devices, where the confidence interval was higher than the 7%. In addition, the results show that the confidence interval did not meet the criteria in highhumidity compared to low?humidity. Therefore, the measurements of particulate matter should be re-considered as their precision, which is not absolute value of the fine dust but is a relative trend. |