The Air Quality Limit Values Regulations 2001

Definitions

2.  In these Regulations—

“agglomeration” means a zone with a population concentration in excess of 250,000 inhabitants, or, where the population concentration is 250,000 inhabitants or less, a population density per km ² for which the Secretary of State considers that the need for ambient air to be assessed or managed is justified;

“alert threshold” has the meaning given by regulation 8(2);

“ambient air” means outdoor air in the troposphere, excluding work places;

“assessment” means any method used to measure, calculate, predict or estimate the level of a relevant pollutant in the ambient air;

“fixed measurements” means measurements taken at fixed sites either continuously or by random sampling, the number of measurements being sufficiently large to enable the levels observed to be determined;

“level” means the concentration of a relevant pollutant in ambient air;

“limit value” has the meaning given in regulation 3(1);

“lower assessment threshold” has the meaning given in regulation 5(5);

“natural events” means volcanic eruptions, seismic activities, geothermal activities, wild-land fires, high-wind events or the atmospheric resuspension or transport of natural particles from dry regions;

“oxides of nitrogen” means the sum of nitric oxide and nitrogen dioxide added as parts per billion and expressed as nitrogen dioxide in microgrammes per cubic metre;

“PM_2.5” means particulate matter which passes through a size-selective inlet with a 50% efficiency cut-off at 2.5 μm aerodynamic diameter;

“PM₁₀” means particulate matter which passes through a size-selective inlet with a 50% efficiency cut-off at 10 μm aerodynamic diameter;

“relevant pollutants” means sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead;

“upper assessment threshold” has the meaning given in regulation 5(5); and

“zone” means a part of the territory of England shown on a map published by the Secretary of State on 19th January 2001, deposited at the offices of the Department for Environment, Food and Rural Affairs, Ashdown House, 123 Victoria Street, London SW1E 6DE and displayed on the Department’s website at http://www.environment.detr.gov.uk.