ZEMCH 2019 International Conference Proceedings April.2020 | Page 279
1. Introduction
There have been continuous necessities to monitor indoor air quality more correctly and selectively
in terms of concentration and type of contaminants. Even though various technologies to detect both
gaseous and particulate contaminants have been developed and widely applied to practical fields,
sensing data to inform us with both contaminant source and its location at the same time does not still
exit [1]. Particulate matter sensing was mostly based on the light scattering principle. As much as
particles exist in a specific volume of space, more light is reflected and less light arrives at the detector.
It has been reported that light sources such as laser diode, infrared, and LED photodiode [2]. For more
accurate concentration, particle counters utilizing Beta ray absorption method were tested and
authorized to report daily data of particulate matters those have aerodynamic diameter less than 10
and 2.5 μm in Korea [3]. Depending on the purpose of measurement, both optical sensing and beta
attenuation monitoring (BAM) were adopted to research area or air pollution forecast, simple light
scattering based sensors were mostly utilized in daily measurement for a single household including
dust sensor, air conditioner and air purifier. As recognized in the above explanations, the concentration
of particulate matter is primary information for sensors in monitoring particulate matter contaminants.
However, other information such as type of particles, chemical composition to inform us with the origin
where it is generated and transported from. Nowadays, source characterization of contaminants,
especially in particulate matters, are one of major concerns in Korea because daily concentration of fine
dust so called, PM2.5 and PM10, is so influential that number of patient with the disease respiratory
system is reported to be noticeably increased and personal protective equipment (PPE) including air
pollution mask, filter and air purifier are sold significantly above production. In several reports,
particulate matters are characterized and chemical compositions are reported that PM10 and PM2.5
contain organic compound (OC) and heavy metal ions, which may induce health issues [4]. So, there is
at least demand to identify the type of contaminants by simple dust sensor at economic cost. In this
study, small scale spectral sensor was utilized to find the feasibility of light wavelength in terms of
position and intensity to discriminate the type of particulate matters. The other approach was to use
chroma meter to reveal color data of particulate matters. Five different particles, soil, household dust,
Korea pine tree pollen, talc powder, and gypsum powder were tested by analyzing the light spectrum
data of reflected light of samples under experimental conditions. It is our expectation that combined
data of reflected light spectrum and color can assist current light scattering principle based sensor to
identify the type of particulate matter contaminants and concentration as well.
2. Materials and Methods
Five different particulate matters were collected and prepared for the characterization. Household
dust was collected by vacuum cleaner. Korean pine tree pollen was collected during spring season in
Korea by washing the glass plate located under the pine tree bush for one day. Illite powder was used
for the representative soil sample and it was purchased from Yong Gung Illite® Inc. Talc powder, raw
material of widely used construction material and usually suspended in air during the construction
was purchased from chemical company and its chemical formula was Mg3H2(SiO3)4; H2Mg3O12Si4.
All five samples were ground and filtered with Whatman® qualitative paper filter having 20 μm
particle retention by flushing with distilled water. After drying at room temperature, collected powders
were used for experiment.
Spectral sensor, Apollo™, developed by NanoLambda in Korea, was used to differentiate reflected
light into light spectrum in a small chamber and its configuration of chamber was described in our
previous study [5]. Chromameter CR‐400 by Konica Minolta was used to acquire color data in terms of
chromaticity values.
Filters and additives to modulate reflected light of particle samples were tested. Cellophane filters
were ranged from red, orange, yellow, green, blue, pink, and violet. Three color filters, dark blue, green,
and yellow were utilized that represents 400~450nm, 500~550nm, and 550~600nm in wavelength,
Optical Sensing Assistance to Enhance Particulate Contaminants Detection
for Indoor Air Quality Monitoring
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