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Table 10 Comparison of pollutant concentrations and sub-indices

From: Building an indoor air quality monitoring system based on the architecture of the Internet of Things

AQI index NO2 (ppb) SO2 (ppb) O3 (ppm) O3 (ppm)[1] PM10 (µg/m3) PM2.5 (µg/m3) CO (PPM)
Air Quality Index (AQI)
Good (0–50) 0–53 0–35 0–0.054 0–54 0.0–15.4 0–4.4
Normal (51–100) 54–100 36–75 0.055–0.07 55–125 15.6–35.4 4.5–9.4
Unhealthy for sensitive groups (101–150) 101–360 76–185 0.071–0.085 0.125–0.164 126–254 35.5–54.4 9.5–12.4
Unhealthy for all groups (151–200) 361–649 186–304 0.086–0.105 0.165–0.204 255–354 54.5–15.4 12.5–15.4
Very unhealthy (201–300) 650–1249 305–604 0.106–0.2 0.205–0.404 355–424 150.5–250.4 15.5–30.4
Harmful (301–400) 1250–1649 605–804 [2] 0.405–0.504 425–504 250.5–350.4 30.5–40.4
Harmful (401–500) 1650–2049 805–1004 [2] 0.505–0.604 505–604 350.5–500.4 40.5–50.4
  1. [1] is the mean of O3 for 8 h
  2. [2] When the AQI is greater than 301, the calculation is based on the hourly values of O3, but not the 8-h value of O3