(1) In these Regulations—
“ the 2021 Act ” means the Environment Act 2021;
“ the 2010 Regulations ” means the Air Quality Standards Regulations 2010 ;
“ ambient air ” means outdoor air, excluding the air in workplaces where members of the public do not have regular access;
“ AQSR monitoring station ” means a monitoring station which is used to measure PM 2.5 levels for the purposes of the 2010 Regulations;
“ fixed measurement ” means a measurement taken at a fixed location, either continuously or by sampling at regular intervals, to determine levels of PM 2.5 ;
“ minimum annual data capture requirement ” has the meaning given in regulation 14(4);
“monitoring station” is to be interpreted in accordance with regulation 12(4);
“ ratified ” has the meaning given in regulation 14(5);
“ year ” means a calendar year;
“ zone ” means one of the zones or agglomerations into which England is divided for air quality monitoring purposes, as determined under regulation 4 of the 2010 Regulations.
(2) For the purposes of these Regulations—
(a) particulate matter is to be treated as meeting the definition of PM 2.5 if it passes through a size-selective inlet with a 50% efficiency cut-off at 2.5 micrometres aerodynamic diameter;
(b) a reference to the “ level ” of PM 2.5 means the mass concentration of PM 2.5 measured in micrograms per cubic metre (“µg/m³”).