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Outdoor Particulate Matter Measurement Technology

Outdoor Particulate Matter Measurement Technology
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Outdoor Particulate Matter Measurement Technology - 1

Outdoor Particulate Matter Measurement Technology Table 1 . PM10 and PM2.5 standard Particulate Matter and Air Pollution Dust with various size suspend in the air, among them particles diameter less than 10pm is called particulate matter (PM10), which is an important part of aerosol in the air, and for those diameter less than 2.5pm is defined as PM2.5. Usually diameter of the finest human air is 50~70pm, almost the limit of vision, whereas both PM2.5 and PM10 are much smaller, even though invisible, their effect is attracting increasing attention and research recently. Virus and other harmful substance like trace heavy metals (contained in automobile exhaust) can be adsorbed on aerosols, and then travel into human body by breath, which may cause respiratory and cardiovascular disease or even lung cancer, also some researches show that infectious disease can spread by aerosol. WHO reported that particulate matter is the main factor of air pollution, and cause death of 3 million people and economic loss of $ 5 trillion every year. Human activities are the main source of particles, including automobile emission, coal combustion, factories, jobsite raised dust, etc., many countries have introduced laws to control air pollution and monitoring outdoor air quality, standard of PM2.5 and PM10 concentration (daily and yearly average basis) of some countries and recommend by WHO can be seen in table 1 below: Measurement of Particulate Matter To measure outdoor particulate matter concentration, many technologies have been developed, and among them, tapered element oscillating microbalances (TEOM), Beta ray and light(usually laser) scattering are widely used recently. TEOM is developed based on relation between mass and oscillation frequency. Particles from sample air are trapped by the filter that fixed on an oscillating part , and then frequency of the oscillating part can be detected, so the mass change can be accurately calculated. This method is of super high accuracy, and available for continuous measurement, but and filter need to be replaced quite often. Beta ray using C14(carbon isotope) source to emit beta ray and penetrate a moving filter on which particles are collected from sample air, on the other side of the filter, G-M tube is installed to detect beta ray after attenuation, and particle mass can be calculated according to the beta ray attenuation. The accuracy is also very high, however the device is expensive and reaction is slow. Both TEOM and beta ray are often used as standard equipment in laboratory or national meteorological, they are of big size, and high cost. Mie scattering is exploited to measure concentration of particle, which is light scattering method, the principle is that pulse signal of light scattered by the particle in sample air is related to the particle size and quantity, with reasonable algorithm and calibration with standard equipment, concentration of particle can be calculated. With the advantages of low cost, small and maintenance-free device, light scattering method is attracting more and more manufactures to invest research, Cubic Sensor and Instrument Co., Ltd. has already dedicated in this field for 10 years, and its products are highly evaluated by users. Cubic Sensor and Instrument Co.,Ltd

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Outdoor Particulate Matter Measurement Technology - 2

Outdoor Particulate Matter Measurement Technology Laser Scattering and Outdoor Air Quality For light scattering method, device is cheap, usually less than 10% of beta ray or TEOM, but the uncertainty is a weak point since the output is based on very weak original signal treatment, and through certain mathematical algorithm and calibration with other standard equipment, as long as algorithm embedding and calibration completed, any vibration of light signal or other change may cause unacceptable error. To ensure the performance, it’s very important to keep stable light signal and sample flow,...

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Outdoor Particulate Matter Measurement Technology - 3

Outdoor Particulate Matter Measurement Technology Exit of highway Grimm Underground Parking Urban Road Urban Road Figure 3. Road test result comparison of PM3006 and Grimm equipment Anti-dust sheath flow design-To prevent dust accumulation on photo diode of the sensor, Cubic developed sheath flow design to separate sample air and lens of photo diode, which can ensure accuracy and lifetime of the sensor. To verify the effect, test is implemented under 5mg/m³ Arizona A2 dust environment for 6 weeks, and result is shown in the table 2 below. Figure 4. Theory of anti-dust sheath flow Table 2 ....

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Outdoor Particulate Matter Measurement Technology - 4

Outdoor Particulate Matter Measurement Technology Constant Power Linear LD-Stable signal is very important to keep the accuracy of sensor, for this purpose, Cubic designed constant power laser diode with feedback control (seen in figure 6), to prevent temperature influence of signal and measuring performance. Also, linear laser with large power is utilized, compared with point power of other manufacturers, particle counting efficiency is much higher, which favors high accuracy, especially when used to measure PM10. As one of the key part, life time of laser is critical for life time of the...

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Outdoor Particulate Matter Measurement Technology - 5

Outdoor Particulate Matter Measurement Technology Sample Air Heater-For particles sensor, it can not differentiate particle or water droplet at similar size, so when the humidity is high or temperature drops lower than dew point, normally particle sensors will get much higher value than real one. Relative test is implemented in a closed laboratory, and the result in figure 8 shows that when the humidity increase, measuring value of both PM2.5 and PM10 increase extremely. To solve this problem, Cubic developed sample air heater with a sponge inside, as shown in figure 9, which matches with...

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Outdoor Particulate Matter Measurement Technology - 6

Outdoor Particulate Matter Measurement Technology of PM2.5 and PM10 concentration will be updated and transfer to website via internet together with other information like temperature and humidity, so citizens can check air quality anywhere conveniently. Also for raised dust monitoring system in construction jobsite, as shown in figure 13, PM3006 can be used to measure PM2.5 and PM10 concentration, real time data can be published for the supervision of citizens and government, and also send to control center of the jobsite, where can start up water spray device to decrease the dust emission...

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