PART 4Monitoring and assessment
Calculation of annual mean PM2.5 level at monitoring stations15
1
The Secretary of State must ensure that, as soon as reasonably practicable after the end of each year, the annual mean PM2.5 level is calculated for each monitoring station.
2
If PM2.5 levels are measured at periodic intervals, the annual mean PM2.5 level at a monitoring station is to be calculated as the mean of all the ratified periodic measurements taken in a year.