An air quality assessment (AQA) is a report that shows a proposed development will not expose people to harmful levels of air pollution, and will not make local air quality worse. In England and across the UK it is a routine part of the planning system: where a site sits in or near an Air Quality Management Area, generates significant traffic, or places new homes beside a busy road, the local planning authority will expect an AQA before it grants permission.
This guide explains, in plain terms, what an air quality assessment is, why planning approval requires one, when you actually need one, and what a competent AQA must contain. If you are a homeowner, developer or architect trying to work out whether your project needs one, start here.
What is an air quality assessment?
An air quality assessment is a study of two things: the exposure of future occupiers to existing pollution, and the impact the development itself will have on air quality — during both construction and operation. It focuses on the pollutants that damage health and that planning authorities regulate, principally nitrogen dioxide (NO₂), fine particulate matter (PM2.5 and PM10) and oxides of nitrogen (NOx).
A typical AQA does four things. It establishes the baseline using Defra background concentration maps and local monitoring data. It checks the site's status — whether it lies in an Air Quality Management Area (AQMA) or a smoke control area. It assesses the development's impact, from construction dust to the extra traffic the finished scheme will generate. And it recommends mitigation where needed, so the scheme is acceptable in planning terms.
Why is an air quality assessment required for planning approval?
The requirement flows from national planning policy. The National Planning Policy Framework (NPPF) expects the planning system to prevent new and existing development from contributing to, or being put at unacceptable risk from, unacceptable levels of air pollution. The government's Planning Practice Guidance (PPG) on air quality sets out how this is handled in practice, and most councils reinforce it through their local plan and validation checklist.
Two industry documents do the technical heavy lifting:
- EPUK & IAQM “Planning for Air Quality” — the standard guidance UK planning authorities use to decide whether an assessment is needed and whether an impact is “significant” (its screening criteria sit in Table 6.2).
- Defra LAQM.TG(22) — the technical guidance behind local air quality management, including how background and roadside concentrations are derived.
For sites in London, the London Plan adds Policy SI 1, which requires development to be at least “air quality neutral”. Your AQA is the evidence that satisfies these policies; without it, an officer has no basis to conclude the scheme is acceptable, so the application stalls or is refused.
When do you need an air quality assessment?
You will generally need an AQA to support a planning application if any of the following apply:
- the site lies within or adjacent to an AQMA;
- the development will generate significant additional traffic, or a material change in vehicle movements or congestion;
- it introduces new sensitive receptors — homes, schools or healthcare uses — close to a busy road or other pollution source;
- it includes combustion plant such as biomass boilers, CHP units or standby generators;
- it involves demolition, earthworks or construction capable of generating dust; or
- the local authority requests one in pre-application advice or its validation checklist.
A quick first step is to check your area on the Defra UK-AIR service and confirm whether you fall inside an AQMA. If in doubt, screen the proposal early — mitigation designed in at concept stage is far cheaper than a redesign after a holding objection from Environmental Health.
The pollutants and objectives that matter
| Pollutant | Key UK objective | Why it matters |
|---|---|---|
| Nitrogen dioxide (NO₂) | 40 µg/m³ annual mean | Mainly from road traffic; the most common reason for AQMAs |
| PM10 | 40 µg/m³ annual mean | Coarse particles from traffic, dust and combustion |
| PM2.5 | England target 10 µg/m³ by 2040 (Environment Act 2021) | Fine particles with the greatest health impact |
An AQA compares predicted concentrations at relevant receptors against these objectives, applying the EPUK/IAQM significance criteria to judge whether the effect is acceptable.
What a good air quality assessment contains
- A baseline built from Defra background maps and nearby monitoring data.
- AQMA and smoke-control screening for the exact site.
- A construction-phase dust assessment following IAQM guidance (v2.2, January 2024).
- An operational assessment of traffic and any combustion emissions, with dispersion modelling where thresholds are exceeded.
- Significance conclusions using the EPUK/IAQM criteria.
- Mitigation and, where relevant, an air-quality-neutral assessment for London schemes.
A report that simply asserts “air quality is fine” without this evidence will not satisfy most Environmental Health officers.
How Fortress Associates can help
Our air quality assessment service produces a site-specific AQA for UK planning applications using live official data — Defra background concentration maps, national AQMA boundaries, monitoring network data and DfT traffic counts. The report is free, follows the IAQM dust guidance (v2.2, 2024), the EPUK/IAQM land-use planning criteria and Defra LAQM.TG(22), and covers every UK local authority. Whether you are planning a householder extension, new homes or a commercial or mixed-use scheme, contact us to get started — or see the full range of what we offer on our services page.
Sources & further reading
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