For the purposes of these Regulations, PM_2.5 levels are to be measured in µg/m³ to at least one decimal place.

The data obtained from fixed measurements of PM_2.5 must be independently checked, and not used for the purposes of any calculations if it is determined that they are likely to be incorrect.

The data obtained from fixed measurements of PM_2.5 at a monitoring station in a year are not to be used for the purposes of any calculations unless the minimum annual data capture requirement is met by the monitoring station in that year.

The minimum annual data capture requirement for a monitoring station is that fixed measurements of PM_2.5 levels are taken, and the data from such measurements are ratified, for at least 85% of the hours in a year, or if measurements are taken at periodic intervals less frequent than hourly, for at least 85% of those periods in a year.

In this regulation—

• “monitoring station” in relation to any time before these Regulations came into force includes any AQSR monitoring station which was in operation at that time;

• “ratified” means that data have been checked in accordance with paragraph (2) and not excluded from being used in calculations.