Hillingdon / Planning, sources and design
Air quality assessment in Hillingdon
Plan your Hillingdon air quality assessment around the sources that matter to the site. ACP supports planning evidence, monitoring and mitigation for road, airport, industrial and development settings.
Connect the AQMA boundary, current policy and representative data with the actual design and operating scenarios.
Discuss your projectPolicy and local designations
DMEI 14, validation and the actual AQMA or Focus Area boundary.
A clear source inventory
Roads, airport-related activity, local plant and background contributions.
Representative evidence
Reference stations, diffusion tubes and separately identified sensors.
01 / Local context
Airport, road and neighbourhood settings
Hillingdon combines airport activity, major roads, industrial land and quieter northern neighbourhoods. The council’s annual report identifies the M4, A40, M25 and A312 alongside Heathrow as important influences. Assess which sources actually affect the site, rather than applying an airport assumption to every address.
Hayes and the southern road network
Review traffic, servicing, bus movements, energy plant and occupied façades together. Where a scheme introduces homes or schools, select representative roadside evidence and coordinate ventilation, overheating and noise.
Heathrow, Harlington and surrounding communities
Separate airport-related operations, access traffic, local roads and background pollution in the source inventory. Use consistent assessment scenarios and explain what each background dataset already includes.
Ruislip, Northwood and Harefield
The north includes different settings and monitored roads outside the designated AQMA. Being outside the boundary does not settle exposure or effects from an individual development, construction programme or combustion source.
Data centres and major construction
Standby-generator testing, operating scenarios and cumulative plant can matter even when routine operation is limited. Include relevant construction and HS2-related works where they share affected receptors; establish actual programmes and sources.
AQMA boundary: the council’s AQMA map and report describes the southern-area designation for annual NO₂ from 1 September 2003, using the A40, Yeading Brook and railway boundary. It does not cover the whole borough. Check the precise map for the site and distinguish AQMA and Air Quality Focus Area status.
02 / Monitoring and trends
Longer-term improvement, mixed recent changes
The May 2026 report covers 2025. Hayes rose from 29 to 32 µg/m³; South Ruislip remained at 20. Both remain below 2019 levels. Trends alone cannot establish the effect of a particular intervention.
Annual NO₂ / 2019–2025
Two roadside histories across Hillingdon
Annual objective: 40 µg/m³
South Ruislip
HI1 · roadside automatic
20µg/m³2025 annual mean
Hayes
HIL5 · roadside automatic
32µg/m³2025 annual mean
Shared 0–60 µg/m³ scale · reported annual measurements at each monitoring location.
Read the annual values
| Year | South Ruislip HI1 | Hayes HIL5 |
|---|---|---|
| 2019 | 34 | 41 |
| 2020 | 16 | 31 |
| 2021 | 27 | 34 |
| 2022 | 28 | 34 |
| 2023 | 24 | 34 |
| 2024 | 20 | 29 |
| 2025 | 20 | 32 |
2025 capture: South Ruislip 99.62%; Hayes 98.33%. Table F, page 36. Check monitor setting and capture before applying these observations to a proposed façade.
03 / Network and interpretation
One reporting year. Different monitoring settings.
The May 2026 annual report covers 2025. Use the same measurement year when comparing these selected stations, then check site type and pollutant-specific data capture.
| Monitoring location | NO₂ | PM₁₀ | PM₂.₅ |
|---|---|---|---|
| HeathrowLHR2 · airport | 2999.59% capture | 1680.66% capture | 980.66% capture |
| South RuislipHI1 · roadside | 2099.62% capture | 2198.95% capture | Not listedTable K |
| HayesHIL5 · roadside | 3298.33% capture | 2793.17% capture | Not listedTable K |
| London HillingdonHIL · urban background | 2596.34% capture | 1795.59% capture | 995.59% capture |
Council ASR: Table F, NO₂; Table I, PM₁₀; Table K, PM₂.₅. “Not listed” means no value appears for that site in Table K; it is not a zero concentration.
Heathrow LHR2 particle capture was 80.66%, compared with 99.59% for NO₂. A shared station name does not imply equal coverage. These are monitoring-location observations, not predictions for a proposed building.
12 continuous sites, 44 tube locations
The 2025 network includes council, Defra AURN and Heathrow stations. Diffusion tubes extend NO₂ coverage; two co-location sites support bias-adjustment checks. Read the adjusted results and QA notes together.
Five separate low-cost sensor sites
Appendix C includes Tavistock Road, Harlington High Street, Harefield Hospital, Green Lane and Heathrow Bath Road. Some series cover only part of 2025. Keep provisional sensor results distinct from reference-monitor evidence.
Background selection should document Defra borough data, local source contributions and the baseline year. Avoid double counting a source included in the background and modelled again explicitly. Do not infer ultrafine-particle concentrations from PM₂.₅ mass data.
04 / Planning requirements
Connect adopted policy with the right evidence
DMEI 14: emissions, exposure and improvement
Development should reduce emissions, achieve at least Air Quality Neutral, protect existing and new sensitive receptors through sufficient mitigation and contribute to improvement, especially within the AQMA. Policy DMEI 14, printed page 87.
EM8, DMEI 1 and airport development
Read Part 1 Policy EM8 with Part 2. DMEI 1 addresses living roofs/walls and vegetation for major development in AQMAs. DMAV 2 requires airport-boundary development to meet DMEI 14 and other environmental requirements. Greening does not replace a source or exposure assessment.
Validation and proposal-specific scope
The live application page links the February 2024 checklist. It lists AQA under relevant full, outline and reserved-matters routes; its definitions also address new development exposed to poor air and certain AQMA/Focus Area schemes. Read the actual application category. Current linked checklist.
Focus Areas and current guidance
Check the council’s Focus Area mapping and project advice alongside adopted policy and current GLA guidance. The annual report describes local improvement and damage-cost workstreams. Explain their basis and applicability; avoid copying a contribution or condition from another permission.
Use the London air-quality guide and tools to organise impact assessment, Neutral benchmarks and any applicable Positive design approach. Older local SPG references in inherited reports need an edition and applicability check against the current framework.
05 / Assessment and design
Turn Hillingdon’s local context into a practical brief
The council’s 2026 report discusses data-centre generation and HS2 construction. The questions below translate those local issues into an assessment brief.
Heathrow and Harlington: separate the sources
Map roads, airport-related sources, industrial neighbours and energy or standby plant relevant to the site. Record emissions, operating hours, stack geometry, testing regimes and uncertainty.
Hayes: connect roads with occupied façades
Use the same façade, room and intake locations across air quality, acoustics, ventilation and overheating. Test practical layout and source-control options while the design can respond.
Data centres: test how generators actually run
Distinguish routine testing, maintenance and emergency operation. Review start-up emissions, exhaust treatment at the expected load, simultaneous plant and nearby sensitive receptors. Agree realistic cumulative scenarios and verifiable operating controls.
HS2 and local works: align the construction brief
Where programmes overlap, review construction routes, dust-generating works and shared receptors alongside HS2 activity. Coordinate dust, noise and vibration controls using the same programme. Assess ecological pathways where emissions may affect designated habitats.
Coordinate air quality assessment, noise and odour using a shared brief and drawings.
06 / Interactive project checklist
Hillingdon 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.
07 / Current changes
Track the draft action plan and plan timetable
The council is consulting on a draft Air Quality Action Plan 2026–2030, with responses due by 20 November 2026. It covers monitoring, the urban environment, cleaner transport, vulnerable groups and awareness. Treat it as a draft action plan while the consultation and adoption process continues. Current consultation and draft plan.
The September 2026 Local Plan timetable supersedes earlier programme dates. It schedules content-and-evidence consultation for April–May 2027 and consideration of adoption in 2029. These are programme milestones, not adopted new policies. Check the current timetable.
Airport-related monitoring, ultrafine particles, standby generation and construction remain useful horizon topics. Confirm the applicable evidence and current GLA, Defra and IAQM editions for the assessment date.
Common questions / Local answers
Hillingdon air-quality FAQs
Is all of Hillingdon in an AQMA?
No. The council’s report describes a southern-area AQMA from 1 September 2003 for annual NO2. Its boundary follows the A40 corridor, Yeading Brook and railway alignment. Check the map for the actual site and distinguish Air Quality Focus Areas.
Which air-quality policy should an application use?
Use adopted Local Plan Part 1 EM8 and Part 2 DMEI 14 with relevant supporting policies, the London Plan and current validation requirements. DMAV 2 also applies to development within the Heathrow Airport boundary.
How much monitoring does the borough report?
The May 2026 report describes 12 continuous sites, 44 NO₂ diffusion-tube sites and five separate low-cost sensor sites for 2025. Match the network, measurement method, data capture and quality status to the assessment question.
What do the latest linked annual results cover?
The May 2026 report covers 2025. South Ruislip HI1 recorded 20 µg/m³ and Hayes HIL5 recorded 32 µg/m³ annual NO2. Capture was 99.62% and 98.33%, respectively.
Do airport sources need modelling for every site?
Their relevance depends on the site and assessment question. Identify road, airport-related, industrial and background contributions, then select representative inputs and scenarios. Avoid double counting sources already included in background data.
Can standby generators require an air-quality assessment?
Yes, their relevance depends on emissions, testing and operating scenarios, stack arrangements, nearby receptors and cumulative plant. Exclusion from a particular Neutral benchmark does not automatically remove local impact considerations.
Is the 2026–2030 action plan adopted?
The current council page identifies it as a draft consultation, with responses due by 20 November 2026. Keep consultation proposals separate from adopted policy and check the status when preparing the application.
Can an existing assessment be reused?
Review its source inventory, background treatment, policy references, plant, traffic, receptor locations and assessment year against the current proposal. Retain representative evidence and update material changes and mitigation assumptions.
Hillingdon / Your next step
Discuss your air quality project
Tell us what you are proposing and where you are in the planning process.
What to include
- Site and proposal. Address or postcode, proposed use and approximate number of homes or floorspace.
- Planning stage. Application reference, any Hillingdon Council request or condition, and your target date.
- Local setting. Road exposure, occupied rooms, ventilation, energy plant and construction phases.
- Existing information. Mention available drawings, previous air quality reports and traffic or plant details.
Start with what you have. You can email drawings or council correspondence using the address below.
Your details are handled under our privacy policy.
Evidence / checked 23 October 2026
Hillingdon guidance and sources
Measurement and publication years are stated beside the results. Check current documents when preparing a submission.
- Council air-quality report gateway
- Current annual-report library
- May 2026 report: 2025 monitoring results
- Adopted Local Plan and maps
- DMEI 14, DMEI 1 and DMAV 2: adopted policies
- Application and validation gateway
- Current linked validation checklist: February 2024
- Council AQMA map and designation
- Draft action plan 2026–2030: current consultation
- Local Plan timetable: September 2026 version
- Defra borough dashboard