Air quality modelling for planning

A new building can change the air around it. The air around it can also affect the people who will live or work there.

Councils in England weigh both when they decide a planning application. This page explains when an air quality assessment comes in, and where computer modelling of the atmosphere fits.

Air quality management areas

Every local authority in the UK reviews the air quality in its area. Where it finds places likely to miss the national air quality objectives, it must declare an air quality management area. It then draws up an action plan to improve the air there.

An area can be one or two streets, or something much bigger. Defra's UK-AIR website shows the areas each council has declared.

When air quality counts in a planning decision

National planning guidance names the kinds of development where air quality may come up.

Schemes that change traffic levels, speeds or the mix of vehicles on local roads.
New sources of pollution, such as biomass boilers, furnaces or chimneys.
New homes, schools or workplaces in places where the air is already poor.
Building work that could send dust towards homes and other sensitive places nearby.
Development that could harm sites protected for wildlife.

The guidance asks applicants to talk to the council's planning and environmental health teams early. Together they agree whether an assessment is needed and how far it should go.

What an assessment covers

An assessment should be in proportion to the scheme and its likely effects. It describes the air quality today, and how it would change with the development and without it.

It sets out the methods used, including how any modelling was checked. It also covers ways to reduce the harm. Those might include keeping homes back from a source of pollution, planting trees as a barrier, filtering and ventilating the air indoors, or controlling dust during building work.

Where dispersion models come in

A dispersion model is computer software that follows a substance as it travels through the atmosphere until it reaches the ground. It shows whether emissions from a site could harm people or the environment nearby.

Industrial sites that need an environmental permit go through a simpler screening step first. The Environment Agency treats an emission as insignificant when it adds less than 1% to the long-term standard and less than 10% to the short-term one. Emissions that cannot be screened out go on to detailed modelling.

The Environment Agency says detailed modelling needs specialist knowledge. A consultant can do it, and anyone planning to do their own is asked to contact the agency first.

The weather behind a model

Weather records are one of the main inputs to a dispersion model. For a permit application, the Environment Agency asks for at least three years of weather data and recommends five.

The modeller has to explain why the data suits the site. The report includes a wind rose, which shows how often the wind blows from each direction and at what speed. It also explains how the model treats hills and nearby buildings.

Dust and odour

The Institute of Air Quality Management publishes guidance on dust from demolition and construction. It is written for developers, their consultants and council environmental health officers. The Institute also publishes guidance on assessing odour for planning, updated in 2026.