Westminster / Planning & development
Air quality assessment in Westminster
Plan your Westminster air quality assessment around City Plan Policy 36, the February 2026 Environment SPD and the July 2026 validation list. Coordinate building emissions, exposure, commercial extract and construction monitoring before the design is fixed.
ACP helps applicants and design teams define the evidence, coordinate the assessment and plan practical next steps.
Discuss your projectLocal guidance
2026 guidance and coordinated environmental design
Your evidence checklist
Use the planner to organise questions and missing inputs.
A coordinated brief
Connect the assessment with the design and programme.
Local context / Sources, exposure and evidence
Westminster air quality: what matters for your site?
Busy roads are one part of Westminster’s air quality picture. The Environment SPD, chapter 2, also prioritises emissions from commercial heating and power, kitchens and construction. Match the assessment to the sources around the site and the people who will use it.
Roadside exposure
Review traffic, servicing, façade positions and ventilation intakes. Marylebone Road’s A501 street canyon and Oxford Street’s kerbside monitors show why location matters. NO₂ and particles warrant attention.
Buildings and kitchens
Identify boilers, generators, fuel use and commercial extract. Consider combustion NOx, cooking particles and relevant VOCs, alongside odour and fan noise. Electric cooking still produces particles from the cooking process.
Works and dust
Demolition, earthworks, plant and construction traffic need a coordinated dust and emissions response. Apply the council’s construction code to the programme, nearby receptors and monitoring arrangements.
Site context: Defra’s Marylebone Road station profile. Source priorities: revised LAEI 2022 Westminster inventory and the council’s SPD.
Designation / Borough-wide
Westminster’s Air Quality Management Area
The whole city has been an AQMA since 9 March 1999. The designation covers NO₂ annual and hourly objectives, and PM₁₀ annual and daily objectives.
The Defra register and council’s 2024 report confirm this designation. Check Air Quality Focus Areas separately when applying planning policy.
Latest dashboard / 2025 monitoring
Seven included NO₂ sites are compliant
Defra’s local authority dashboard displays 2025 results from Westminster’s 2026 LAQM report. Its seven included NO₂ records meet the objectives. Oxford Street (Selfridges) records 27.7 µg/m³; Covent Garden records 21.5 µg/m³.
This is a selected reporting dataset: additional national and local monitoring sits outside the dashboard. Use the full site evidence when assessing exposure. The AQMA remains in force.
Checked 19 October 2026. The charts below retain the consistent 2018–2024 council-report series; the newer dashboard update is identified separately.
Measured trends / 2018–2024
Three locations. A clearer long-term picture.
Annual mean NO₂ · identical scales in all three panels
Marylebone Road
Kerbside
32.5µg/m³ · 2024
Oxford Street
Selfridges · kerbside
29.5µg/m³ · 2024
Covent Garden
Urban background
18.7µg/m³ · 2024
View annual NO₂ data and quality notes
| Year | Marylebone | Oxford St | Covent Garden |
|---|---|---|---|
| 2018 | 85 | 63 | 39 |
| 2019 | 63 | 55 | 39 |
| 2020 | 44 | 34 | 21 |
| 2021 | 43 | 34 | 24 |
| 2022 | 45 | 37.3 | 23.5 |
| 2023 | 42 | 32.4 | 21.3 |
| 2024 | 32.5 | 29.5 | 18.7 |
Source: 2024 Annual Status Report, Table D, page 11. Covent Garden’s 2024 value is annualised: data capture was 71%. Marylebone capture was 86%; Oxford Street 100%. The chart shows selected sites rather than a borough average.
Diffusion tubes: a wider view of local NO₂
The council reports 27 diffusion-tube sites in its 2024 annual report. Its data portal also includes separate city-wide, Soho, HS2, school and Oxford Street surveys. These have different dates and coverage; co-located triplicate tubes are not three independent locations.
| Location | 2022 | 2023 | 2024 |
|---|---|---|---|
| Charing Cross Road · DT7 | 50.1 | 47.6 | 44.7 |
| Park Lane · DT9 | 35.7 | 32.3 | 31.2 |
| Lisson Grove · DT12 | 20.9 | 19.5 | 17.6 |
Charing Cross Road remained above 40 at the tube in 2024; the report’s receptor-adjusted estimate was 32.4. These are different locations. Source: 2024 report, Tables E and R; cross-checked against the adjusted data export.
The monthly export reaches March 2026 for the city-wide survey in the download checked on 19 October 2026. Its adjusted annual export currently ends in 2024. Use the adjusted annual series for annual comparisons and inspect sampling coverage before interpreting shorter campaigns.
Fine particles and the wider monitoring network
The 2024 report records PM₂.₅ annual means of 13.4 at Oxford Street, 12.7 at Covent Garden and 7.3 µg/m³ at Elizabeth Bridge. Their annual data capture was 81.4%, 90.5% and 90.6%. These provide a separate reason to address particle sources and exposure.
Source: Table I, page 20. Historical PM₁₀ results also appear in the 2023 report. Changes in stations and instruments affect comparisons.
Defra’s Marylebone Road network listing covers NO₂/NOx, PM₁₀, PM₂.₅, ozone, SO₂ and CO, plus specialist measurements including benzene, black carbon and particle number. The assessment scope should identify which additional pollutants are relevant to the proposal’s fuels, processes and receptors.
Recent conditions and the longer record
Use Defra’s latest seven-day Marylebone Road graph for recent hourly conditions and the council’s reference-station downloads for local time series. Recent readings are provisional and short periods can be strongly affected by weather.
The 2022, 2023 and 2024 annual reports show the longer context. Some earlier tables use receptor-adjusted results; the chart above consistently uses the latest report’s monitoring-location series. Select representative sites and periods before drawing a conclusion about a development.
Evidence checked: 19 October 2026. Latest council-listed annual report: 2024, published September 2025.
01 / Local requirements
Westminster policy and the evidence your application needs
Use City Plan Policy 36: Air Quality with London Plan Policy SI1 and the February 2026 Environment SPD. The SPD explains how the adopted development plan applies to proposals. Record relevant neighbourhood-plan policies and site designations in the project brief too.
When does Westminster request an assessment?
Validation requirement L10, page 14, identifies four routes:
- Major development.
- Potentially polluting uses or combustion technologies.
- Sensitive uses, including schools, hospitals, nurseries and specialist care accommodation.
- New homes within an Air Quality Focus Area.
Check the council’s policies map against the actual site boundary. The relevant application routes include full and outline applications, reserved matters and condition variations.
Neutral and Positive evidence
L10 asks for Air Quality Neutral calculations for major development and proposals incorporating combined heat and power. It identifies Air Quality Positive statements for major schemes in Opportunity Areas or Housing Renewal Areas, and developments subject to EIA.
The SPD explains the wider Neutral approach, including how proposals with no additional relevant emissions can explain their position. A Neutral calculation does not replace an assessment of effects on people nearby.
Make the report easy to check
Chapter 2 of the SPD covers the assessment scope and supporting information. Keep baseline evidence, model assumptions, traffic and energy inputs, mitigation and construction effects traceable. Explain how the conclusions relate to the submitted drawings.
Where the project changes, review the assessment inputs as well as the drawing numbers. New plant, altered servicing, floor area or a different use can affect the evidence needed.
Sources checked: 19 October 2026. Adopted policy, supplementary guidance and validation requirements serve different purposes; the scope should reflect the actual proposal.
02 / Practical approach
Resolve environmental interfaces early
Keep ventilation intakes, discharge points, occupied spaces and servicing on a coordinated drawing set. Then review how the air quality response interacts with noise, overheating and local environmental controls.
Where a project includes commercial uses, describe the activities and plant in enough detail to define the assessment scope. Record changes as the design develops.
Illustrative project brief
A refurbishment combines occupied accommodation, commercial servicing and new plant. A shared environmental plan can help the team compare intake and discharge positions before procurement decisions are fixed.
Construction / Dust and monitoring
Build the construction programme around Westminster’s code
The 2026 construction code applies to new sites from 1 June and existing sites from 1 September 2026. Confirm the project level and the relevant condition. Levels 1–2 use a Site Environmental Management Plan; Level 3 basement projects use a Construction Management Plan.
Chapter 7 of the May 2026 code covers the Air Quality Dust Management Plan. Levels 1–2 require continuous PM10 and PM2.5 monitoring with alarms; agree locations, thresholds and responses with the council. Level 3 monitoring is considered individually. Equipment must meet the code’s performance requirements.
Set out activities, receptors, mitigation, monitoring, reporting and response actions together. Allow time to agree the arrangements before work begins.
03 / Interactive project checklist
Westminster evidence planner
Answer five questions to organise the assessment brief. Choose “Not sure yet” where information is missing; those points remain visible in your results.
Answers stay in this page. The planner organises evidence; it does not certify compliance or decide planning requirements.
04 / A clear assessment package
From the brief to the planning evidence
01 / Scope
Define the question
Bring together the local requirement, proposal, sources and receptors. Identify missing information before detailed work begins.
02 / Assess
Use consistent inputs
Align the baseline, traffic, plant and programme. Explain assumptions and compare relevant scenarios.
03 / Respond
Connect findings to design
Record mitigation and the drawings or specifications it relies on. Review material changes as the project develops.
Our London Neutral and Positive evidence planner helps organise the wider policy workstreams. For construction, use the London assessment and monitoring guidance alongside the site-specific brief.
Where extract, fan noise or sensitive neighbours are involved, coordinate the noise assessment and odour assessment with the same plans. The main air quality service page explains the broader assessment and monitoring services.
Policy horizon / Checked 19 October 2026
What is changing for Westminster projects?
Local: construction plant and power
The adopted code includes a forward programme for site power and lower-emission machinery. Tables 5–7 set milestones from January 2027, varying by project level and equipment. Check these against procurement and the works programme.
London: emerging plan
The Draft London Plan is emerging policy. Its general consultation deadline of 15 October 2026 has passed; assess its current status and weight separately from adopted Policy SI1.
National: fine particles
Defra’s interim PM2.5 planning guidance supports reducing emissions and exposure through design. National targets should inform the assessment context; they are not a universal site-specific permission threshold.
Professional guidance: use published editions
IAQM currently lists the 2017 planning guidance, 2024 construction dust guidance and 2018 construction monitoring guidance. Revisions are in progress. An estimated consultation date does not establish a new published method.
05 / Send what you have
Start your Westminster air quality brief
Send the information available now. These details help us identify the next assessment steps and prepare an appropriate scope:
- Site address, plans and planning reference.
- Proposed use, scale and application stage.
- Council comments, conditions and relevant deadlines.
- Traffic, servicing, energy and extract information.
- Occupied spaces, windows and ventilation proposals.
- Construction activities and intended programme.
- Existing reports, monitoring and material design changes.
For this project, pay particular attention to: 2026 guidance and coordinated environmental design.
06 / Local project questions
Westminster air quality questions
When might a Westminster application need an air quality assessment?
Check requirement L10 in Westminster’s July 2026 validation list. Major development, sensitive uses and new housing in an Air Quality Focus Area are relevant starting points. Review the proposed emissions, site designations and occupied locations against the full requirement.
Is the whole of Westminster in an Air Quality Management Area?
Yes. The borough-wide AQMA covers nitrogen dioxide and PM10 objectives. It is different from an Air Quality Focus Area. The designation does not mean every location currently exceeds an objective; use the latest monitoring evidence alongside the site context.
Do improving pollution levels remove the need for an assessment?
No. Borough trends provide context, but an application still needs to address its own emissions and exposure. A compliant monitoring station cannot establish conditions at every façade, intake or nearby sensitive receptor.
Can existing council monitoring data be used?
Council and reference-network data can inform the baseline. Check the location, pollutant, year, data capture and adjustment methods before relying on a result. Decide whether additional site monitoring is needed for the project’s exposure and assessment questions.
Which pollutants should the assessment consider?
NO₂ and particulate matter are key starting points. Review PM10 and PM2.5 as appropriate, together with the proposed sources and sensitive receptors. Combustion, construction and cooking can require different evidence; odour and ecological effects need consideration where relevant.
Does a construction dust assessment also cover site monitoring?
They are separate tasks. The assessment identifies risks and controls; monitoring checks conditions during works. Westminster’s May 2026 Code of Construction Practice sets requirements by project level. Confirm the applicable registration, dust controls, monitoring and alarm arrangements before works begin.
How should plant or commercial kitchen proposals be assessed?
Describe the equipment, fuels, exhausts, operating hours, servicing and neighbouring receptors. Coordinate the air quality evidence with noise, odour and ventilation design, using consistent intake and discharge drawings.
What information should I send to start the assessment?
Send the site address, plans, proposed uses, application stage and council comments. Include plant or extract details, traffic and servicing changes, construction scope and existing reports. These inputs help define the evidence, mitigation and programme needed.
Westminster / Your next step
Discuss your air quality project
Send the site, proposal and planning stage. Include any council request and programme constraints so ACP can identify the assessment steps.
Your details are handled under our privacy policy.
Sources / Current local and wider guidance
Westminster sources and further reading
- City Plan 2019–2040 (2026): Policy 36
- Environment SPD, February 2026: chapter 2
- July 2026 validation list: L10, page 14
- Construction code: current application and project levels
- Code of Construction Practice, May 2026: chapter 7
- IAQM: published guidance and revision programme
- Draft London Plan: emerging policy
- Defra: PM2.5 planning guidance
Source review: 19 October 2026.