# Development of Multi-Item Air Quality Monitoring System Based on Real-Time Data
## 3 Results and Discussion
### Verification of Multi-Item Air Quality Monitoring System  
In order to test the reliability of the developed device, a comparative test with other specialized environmental devices, an accuracy test, and an operating temperature test were conducted. Comparative test items were PM\({}_{10}\), PM\({}_{2.5}\), O\({}_{3}\), NO\({}_{2}\), CO, and SO\({}_{2}\). The accuracy test items were temperature and humidity. The operating temperature test range was \(-20\)\({}^{\circ}\)C to 60 \({}^{\circ}\)C. Eight out of the sixteen items were tested; the other items are scheduled to be conducted through a closed chamber test through an accredited testing laboratory.  
First, in the comparative test, the values were compared by installing the developed device at the measurement point and the same point of AirKorea (Korea government official atmospheric information site). The environmental measuring instruments used in AirKorea are PM\({}_{10}\) for Spirant BAM by Ecotech (Hyderabad, India), PM\({}_{2.5}\) for BAM 1020 by Met one Instrument, O\({}_{3}\) for Serinus 10 by Ecotech (Hyderabad, India), NO\({}_{2}\) for Serinus 40 by Ecotech (Hyderabad, India), CO for Serinus 30 by Ecotech (Hyderabad, India), SO\({}_{2}\) for Serinus 50 by Ecotech (Hyderabad, India). They are all environment-specialized measuring devices. They were all tested for a quality device using a professional purpose by the Korea Ministry of Environment. Figure 7 shows the difference between the developed device and AirKorea measuring device for six items (PM\({}_{10}\), PM\({}_{2.5}\), O\({}_{3}\), NO\({}_{2}\), CO, SO\({}_{2}\)). The total test duration was 14 days, and 100 h of data were compared. The difference in values is \(\pm 5\%\) for PM\({}_{10}\), \(\pm 6\%\) for PM\({}_  
it was confirmed that the measurement trend of the developed device is not significantly different from the existing specialized environmental measurement device.  
Figure 7: Comparative test between the developed device and Airkorea data. (**a**) PM\({}_{10}\) results; (**b**) PM\({}_{2.5}\) results; (**c**) O\({}_{3}\) results; (**d**) NO\({}_{2}\) results; (**e**) CO results; (**f**) SO\({}_{2}\) results.  
The temperature and humidity test in Figure 8 was processed in a closed chamber at the nationally accredited testing institution. For the test, a closed chamber was set to a temperature of 40 \({}^{\circ}\)C and a humidity of 80%. The test was run for 1200 s and showed an accuracy of 99% for temperature and 98% for humidity. Currently, accuracy tests are being conducted at temperatures of 0 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 40 \({}^{\circ}\)C, and 60 \({}^{\circ}\)C and humidity of 20%, 40%, 60%, and 80%.  
The operating temperature test was confirmed through a closed chamber system of a nationally accredited testing institute. The temperature was divided into nine stages from 20 \({}^{\circ}\)C to 60 \({}^{\circ}\)C, and the normal operation of the device was checked. The test time was 130 min, and the result is shown in Figure 9. It was confirmed that the device works well without any problems between \(-\)20 \({}^{\circ}\)C and 60 \({}^{\circ}\)C.  
Therefore, the result shows that the developed system has a positive use for a specialized air quality measurement device. However, it is not enough to prove the reliability of the developed device considering that the tests conducted are only the comparative test and the simple temperature test. When all installed sensors are tested in a closed chamber and the time and number of tests are sufficient, the device will have a full guarantee for  
Figure 8: Temperature and humidity accuracy test result by the developed device and the closed chamber environment.  
(**a**) Temperature result; (**b**) humidity result.  
Figure 9: Operating temperature test result by the developed device and the closed chamber environment.  
a professional environmental measuring device. Other tests--all sensors in the closed chamber and a comparative test with increased time--are in progress.