Table 2.

Threshold values of ambient air pollutant indicators in GB 3095-2012.

No.	Pollutant Indicator	Average Time	Threshold Values		Unit
			Level I	Level II
1	SO2	Annual mean	20	60
		24-hour average	50	150	µg/m3
		1-hour average	150	500
2	NO2	Annual mean	40	40
		24-hour average	80	80	µg/m3
		1-hour average	200	200
3	CO	24-hour average	4	4	mg/m3
		1-hour average	10	10
4	O3	8-hour average	100	160	µg/m3
		1-hour average	160	200
5	PM10	Annual mean	40	70	µg/m3
		24-hour average	50	150
6	PM2.5	Annual mean	15	35	µg/m3
		24-hour average	35	75