Tab. VI.1 The rules for the announcement and cancelling of smog situations and regulations (alerts)

	Threshold value			Exceedance duration	Number of stations	Supplementary condition
	Abbreviation	µg.m-3	Interval
Announcement of smog situation
PM10	IPH	100	24 h	2 days (i.e. 25 h)	1 station	Increasing trend of the running 12-hour averages of PM10 in at least half of the stations over the past six hours.
NO2		200	1 h	3 h		—
SO2		250				—
O3		180		1 h		—
Announcement of regulation (alert)
PM10	RPH	150	24 h	3 days (i.e. 49 h)	50 %	Increasing trend of the running 12-hour averages of PM10 in at least half of the stations over the past six hours.
NO2		400	1 h	3 h		—
SO2		500				—
O3	VPH	240		1 h	1 station	—
Cancellation
A regulation (alert) or smog situation is cancelled if no respective threshold values are exceeded at any measuring station representative for the pollution level in the given area and this state continues without interruption for at least 12 hours (in the case of PM10, the running 24-hour average concentration is lower than the respective threshold value for at least 12 consecutive hours) and the reappearance of the meteorological conditions which cause a smog situation is not anticipated based on meteorological forecasts over the course of the 48 hours following the pollution levels decline below the threshold values. The time interval of 12 hours shall be reduced up to three hours if the meteorological conditions are not considered to be capable of causing a smog situation and it is effectively ruled out that such conditions will reoccur over the next 48 hours based on the meteorological forecast.

Note: IPH – informative threshold value, RPH – regulatory threshold value, VPH – alert threshold value. The requirements for the number of stations are related to the representative stations for the given SVRS area.