An air quality assessment is often a requirement by the local planning authority to support a planning application, to assist the decision-making process. The requirement and scope of an air quality assessment is driven by national, regional and local planning policy, legislation and guidance. 

Air quality assessment requirements differ between local authority areas dependant on the local planning policies. For example, emissions mitigation assessments is often a  requirement in Sussex, and Air Quality Neutral Assessments and Air Quality Positive Statements may be required in London.