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AIR QUALITY · PLANNING & DEVELOPMENT · HILLINGDON

Air quality assessment for planning in Hillingdon.

ACP provides air quality assessments for planning, dispersion modelling and practical mitigation advice. We help developers, architects and planning teams address council requirements and make informed design decisions.

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Expert-led · 15+ years’ experienceLocal authority & private-sector expertiseResearch-informed technical assessmentsPractical advice for planning and design

YOUR SITE. YOUR COUNCIL. YOUR ASSESSMENT.

Where is your development?

Choose your region, then a council or county profile. Open the local requirements, assessment considerations and answers for your project.

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YOUR LOCATION / YOUR PLANNING BRIEF

National expertise.
Local planning context.

Your development’s location shapes the assessment brief. The council selected above shapes the local brief below. Our assessment then connects those requirements to your site and design.

LONDON / LOCAL PLANNING EVIDENCE

Hillingdon: what your submission needs to address.

Hillingdon’s DMEI 14 combines emission reductions, Neutral development and protection of both existing and future sensitive receptors.

Policy expectation

Demonstrate appropriate emission reductions and, as a minimum, Air Quality Neutral development.

Protect receptors

Provide sufficient mitigation to avoid unacceptable air-pollution risks to existing and new sensitive users.

Improve air quality

The policy expects an active contribution to improvements, particularly within the AQMA. Relevant proposals need a future air-quality assessment.

Local source and review status

Local Plan Part 2, policy DMEI 14 →

Published council guidance · Reviewed 20 October 2026.

Discuss your Hillingdon project →

Start your Hillingdon brief

For this London project, include the proposed use and floorspace, energy or combustion-plant strategy, transport information and any council comments. We will separate local exposure, construction effects and the applicable Neutral or Positive evidence.

We will identify the required evidence, information gaps and appropriate deliverables in the quotation. Monitoring, detailed modelling and condition-discharge work are scoped where needed, rather than assumed for every site.

Discuss the site and assessment scope →

01 / GET THE RIGHT ASSESSMENT

Resolve the planning question.
Build the right evidence.

Air quality is about both what a development emits and the conditions its future occupants will experience. We examine those questions together, then focus the work on what matters for your site.

01

Planning air quality assessments

For new homes, changes of use, commercial schemes and mixed-use development. Establish the existing conditions, assess relevant impacts and explain how the proposal responds.

Your outcomeA clear planning report and practical recommendations.

Explore the assessment →
02

Dispersion modelling & exposure

Where screening cannot answer the question, test pollutant concentrations at relevant locations. Compare scenarios and investigate the implications for building layout or operation.

Your outcomeEvidence to inform design and mitigation choices.

See what we test →
03

Construction dust assessments

Examine demolition, earthworks, construction and trackout. Translate the dust risk into controls the project team can carry into construction planning.

Your outcomeA risk-based mitigation schedule for the works.

Understand the dust assessment →
04

London Neutral & Positive

Address the London Plan air quality requirements alongside the wider assessment. Connect building emissions, transport and opportunities to improve the design.

Your outcomeA documented policy response, with clear calculations.

See the London requirements →
Has the council asked for a report?Send us the exact request or planning condition. We can work from an early concept, a submitted application or a requirement to discharge a condition.Send your brief →

02 / TECHNICAL DEPTH, PRACTICAL VALUE

A clear line from evidence
to planning advice.

Our starting point is a defensible assessment question. We connect the site context, input data and assessment method to conclusions that your design team and planning officer can follow.

A

Establish the planning context

Review the proposal, local validation requirements and the issues raised by the council. Identify relevant air quality management areas, nearby sources and sensitive uses. Agree the assessment scope and any necessary officer engagement.

B

Build a representative baseline

Review local monitoring, background concentrations and the surrounding road and land-use context. Check the age, location and coverage of evidence. A monitor some distance away may describe background conditions without representing a busy road frontage.

C

Assess construction and operation

Separate temporary construction effects from the completed development. Consider changes in emissions and exposure at proposed and existing receptors. Use screening, detailed assessment or modelling according to the question and available evidence.

D

Turn findings into design actions

Explain the significance of the results, where mitigation is needed and what the design team should do next. Make assumptions visible and connect recommendations to drawings, specifications and the planning submission.

A CLOSER LOOK / DISPERSION MODELLING

Model the development.
Test the decisions.

A useful model answers a specific question: how might concentrations change, which receptors matter and what difference would a design measure make?

Road traffic, background pollution, weather and building context shape the assessment. Where combustion plant is relevant, source characteristics and operating assumptions also matter.

Discuss your modelling brief →
Define the scenarios

Separate the baseline from future conditions. Compare the development with the appropriate future baseline and test mitigation where needed.

Place receptors deliberately

Assess relevant existing properties, proposed accommodation and sensitive uses. Consider façade position, height and potential air-intake locations.

Check inputs and sensitivity

Record traffic and emissions assumptions, background data and meteorology. Where suitable observations exist, use them to check model performance.

Explain the result

Present concentrations and changes against the relevant criteria. Describe uncertainty and the implications for the proposal, rather than leaving the client with an unexplained output table.

Method references: IAQM planning guidance and national planning guidance. Specialist permitting work has its own scope and Environment Agency reporting requirements.

03 / WHAT THIS MEANS FOR YOUR DESIGN

Advice that reaches
the drawing board.

The value of an assessment is what your project team can do with it. Early advice gives you time to consider options while the layout, servicing and ventilation strategy are still flexible.

ILLUSTRATIVE DESIGN EXAMPLE

New homes beside
a busy road

ACP concept section: road emissions, façade assessment points at three heights, a candidate roof-level intake, courtyard receptors and internal layout. Numbered design considerations are explained below.

Concept only. The assessment must establish which options work for the actual site.

One development. Several connected questions.

A road-facing residential scheme may need more than a statement about the nearest monitoring station. The assessment should examine the exposure at the proposed accommodation and how it interacts with the design.

  1. Locate the concern. Identify the relevant road sources, façades, floors and sensitive spaces.
  2. Test the options. Investigate whether changes to layout, intake position or the ventilation strategy address the identified issue.
  3. Coordinate the disciplines. Review the interaction with acoustic design, overheating and building-services requirements.
  4. Make the recommendation buildable. Record the agreed measures and the information that must appear in the design or specification.

A recommendation should tell your team what to change, where to change it and why it matters.

  1. Façade exposureAssess relevant floors and façades, including opening windows and sensitive rooms.
  2. Intake positionTest the candidate position, height and nearby sources before specifying ventilation.
  3. Courtyard conditionsAssess amenity areas and rear façades too; shelter does not establish lower exposure.
  4. Layout & ventilationCoordinate air quality with noise, overheating and building-services design.

DISTANCE / HEIGHT / DESIGN

Explore the evidence.
Shape the design.

Three connected views explain how we turn a pollution question into an assessment brief. Select a view to explore the technical detail.

1 / DISTANCE

How far does the road influence the site?

Roadside NO₂ often falls towards the background with increasing distance. Assess the relevant façades and amenity spaces, rather than assume a universal setback.

Conceptual concentration profile with distance from a road; not measured values.
Original ACP illustration. Concept only; not a modelled result for your site. Open full-size figure →

2 / HEIGHT

What changes between street level and upper floors?

London roadside monitoring supports a decrease in NO₂ with height in studied conditions. Building geometry, wind and other sources affect the profile at your site.

Conceptual distance and vertical profiles, showing why height needs site-specific assessment.
Original ACP illustration. Concept only; not a modelled result for your site. Open full-size figure →

3 / DESIGN

Which receptors and intake positions need testing?

Compare sensitive rooms, façades, outdoor spaces and possible intake positions. Connect the findings to layout, ventilation, noise and overheating decisions.

Conceptual building receptors and intake options; no safe floor or guaranteed mitigation is implied.
Original ACP illustration. Concept only; not a modelled result for your site. Open full-size figure →

Technical context: TfL roadside concentration patterns and the WSP height study hosted by Camden. These support the concepts; ACP’s figures do not reproduce the studies’ measurements.

04 / RESEARCH-INFORMED THINKING

Look beyond
the average.

Traffic, air pollution, noise and weather interact. Understanding those relationships makes the evidence more useful.

Our approach draws on doctoral research examining these connected datasets: aligning observations, investigating patterns and considering how measurement coverage affects interpretation.

That thinking informs a simple discipline: understand the data before drawing a conclusion. For your project, it means explaining what the evidence supports and connecting the findings to a clear decision.

01 / TIME

Are we comparing like with like?

Traffic counts and pollution measurements may cover different periods or sampling intervals. Aligning them helps avoid misleading comparisons.

02 / CONDITIONS

What changed besides traffic?

Wind and other weather conditions influence dispersion. A change in concentration should be examined alongside the surrounding conditions.

03 / COVERAGE

Does the evidence represent the site?

Location, missing observations, calibration and season all affect interpretation. A short monitoring period is not automatically an annual picture.

04 / DECISIONS

What does the client do next?

Translate the analysis into an assessment route, a design question or a targeted evidence gap. Make the next step explicit.

05 / CONSTRUCTION

Control dust risk
before work starts.

A construction dust assessment considers the activities that generate dust and the sensitivity of the surrounding area. Demolition, earthworks, construction and trackout can require different controls.

We turn the assessment into practical requirements: material handling, stockpiles, vehicle movements, housekeeping and a clear response when site conditions change. Where monitoring is needed, the brief should explain its purpose and how results will trigger action.

Assess Activity, scale, receptors and risk.

Specify Controls linked to the actual works.

Implement Responsibilities, checks and response measures.

Assessment framework: IAQM demolition and construction dust guidance, version 2.2.

06 / LONDON & REGIONAL POLICY

Neutral, Positive
and the wider assessment.

In London, Air Quality Neutral assesses building and transport emissions against separate benchmarks. It does not replace the need to consider local exposure or the development’s impacts.

Air Quality Positive takes a wider design approach for relevant large-scale proposals. It looks for opportunities to improve air quality from the start, rather than treating it as a final calculation.

We connect these requirements with the scheme’s energy, transport and layout decisions. Outside London, the assessment responds to the relevant council’s requirements and the site context.

Neutral Benchmark building and transport emissions.

Positive Identify and embed wider design benefits.

Local impacts Assess the people and places affected.

Policy basis: GLA Air Quality Neutral guidance and Air Quality Positive guidance.

07 / A REPORT YOUR TEAM CAN USE

Clear findings.
Traceable evidence.
Practical next steps.

The report should make the technical case easy to follow. The final contents reflect the agreed scope, with detailed modelling or specialist assessments included where commissioned.

ACP CONSULTANTS

Air quality
assessment

PLANNING & DEVELOPMENT

Illustrative report cover

What a well-scoped assessment gives your project
Report componentWhat it helps you understand
Site & policy contextThe proposal, assessment questions and applicable planning requirements.
Baseline evidenceThe sources, receptors and data used to describe existing conditions.
Method & assumptionsThe chosen approach, inputs, scenarios and relevant limitations.
Results & significanceWhat the assessment finds and why it matters for the development.
Mitigation & design adviceThe measures to incorporate and the decisions still required.
Technical appendicesSupporting calculations, receptor details and modelling information where applicable.
Already have a report or council comments?Send the existing assessment and the outstanding questions. We can scope a focused review and response.Discuss a review →

AIR QUALITY & ECOLOGY

Protect people.
Assess habitats too.

A planning assessment can also need to address sensitive habitats. Consider the emissions pathway beyond the development boundary, including traffic on the wider road network. Planning guidance →

01 / SOURCE

What changes?

Traffic, combustion plant, industrial processes or agricultural emissions.

02 / PATHWAY

Where does it travel?

Pollutants disperse in air; nitrogen can reach vegetation and soils through dry and wet deposition.

03 / RECEPTOR

What is sensitive?

Identify the habitat, its designated features and the ecological evidence needed.

Concentrations: critical levels

Assess relevant gases, including NOₓ and ammonia (NH₃), against the applicable ecological critical levels. Airborne concentration is normally expressed in µg/m³.

Deposition: critical loads

Assess nitrogen arriving at the habitat against its nutrient-nitrogen critical load, usually in kg N/ha/year. Consider acid deposition separately where relevant. The appropriate value depends on the habitat.

Concentration and deposition are different measures: a human-health NO₂ result does not answer the ecological question. APIS explains the distinction →

WHEN HRA ENTERS THE BRIEF

Evidence for a planning decision.

For a protected habitats site, screening considers likely significant effects alone and in combination with other plans or projects. Where these cannot be excluded, the competent authority must undertake an appropriate assessment.

The applicant supplies supporting evidence. ACP’s air quality work can inform that evidence alongside ecological interpretation; the authority makes the statutory HRA decision. Read the national HRA guidance →

What the assessment should connect

  • The emissions source and affected roads or plant.
  • Receptor locations, sensitive features and conservation objectives.
  • Background conditions, project contributions and relevant combined effects.
  • Model assumptions, uncertainty and any mitigation evidence.

Natural England’s standing advice covers specified development types and protected sites in England. Its scope excludes local plans and nationally significant infrastructure projects. SSSI protection and HRA are distinct assessment routes. Check the applicable advice →

Is this just “NO₂ deposition”?

NO₂ is relevant, but the wider assessment concerns reactive nitrogen. Oxidised nitrogen from NOₓ and reduced nitrogen associated with ammonia can contribute to deposition. Excess nitrogen can change nutrient-poor habitats; acidity can also matter. Use the pollutants and pathways relevant to the actual source. Defra’s ecological context →

Does every development need a detailed model or an HRA report?

No. Establish the source–pathway–receptor connection and the applicable assessment route first. A screening threshold must be used within its stated guidance and assumptions. It is not a universal permission to ignore small contributions.

Can mitigation be used to avoid HRA appropriate assessment?

Measures intended to avoid or reduce harmful effects on a habitats site are not taken into account at the screening stage. Appropriate assessment considers mitigation and the evidence for its effectiveness. HRA stages and mitigation →

Is atmospheric nitrogen the same as nutrient neutrality?

No. Atmospheric deposition and nutrients reaching a water catchment involve different pathways and evidence. A project may need both examined. Biodiversity net gain also has a different purpose and does not replace a protected-site assessment.

Local examples: check the actual requirement

These local examples illustrate different planning circumstances. They are not an exhaustive England-wide HRA audit, and do not impose a blanket assessment requirement.

Cornwall Council validation update

The council flags protected-site air pollution advice for traffic-generating, agricultural and industrial proposals. It identifies circumstances needing detailed assessment and says its validation guide will be updated.

Use the current update alongside the application checklist; do not infer that every proposal requires a detailed model.

Read the council source →
Epping Forest Applicant guidance, January 2025 update

The council identifies vehicle-related atmospheric pollution as a pathway affecting Epping Forest SAC. Its guidance explains when project-specific HRA information may be needed.

Check the proposal against the modelled scenario and mitigation relied upon. The recreational zone is not a universal air-pollution screening distance.

Read the council source →
Waltham Forest Published applicant requirements

The council asks applications creating one or more new homes to include project-level HRA screening and appropriate-assessment information, with forms for sites inside and outside 400 metres.

Follow the council template. This HRA requirement alone does not establish a requirement for detailed air dispersion modelling.

Read the council source →
Redbridge Published Epping Forest SAC guidance

The council identifies recreation and vehicle-related air pollution as separate concerns, and sets out HRA arrangements for qualifying residential proposals and prior approvals.

Check the mapped zone, proposal type and applicable procedure. Recreational contributions should not be described as air-pollution mitigation.

Read the council source →
Wealden / Ashdown Forest Published evidence base

The council links traffic, air quality and nitrogen deposition to Ashdown Forest SAC and publishes monitoring and modelling evidence.

This is evidence of a relevant pathway, not a current blanket validation trigger. Confirm the project-specific scope with the council.

Read the council source →
New Forest National Park Historic plan HRA: context only

The 2018 plan assessment examines NOx, ammonia and deposition with ecological interpretation of sensitive habitats.

Historic strategic evidence does not set today’s project threshold. Confirm current application requirements and any reliance on strategic evidence.

Read the council source →

Has the council requested ecological air quality or HRA evidence? Send us the request and site details →

Sources checked 20 October 2026. Local requirements, source status and project-specific scope must be confirmed when commissioning.

YOUR QUESTIONS / ANSWERED

Hillingdon planning context

Your Hillingdon questions, answered.

Local planning context first. Clear answers on the assessment, costs and information we need.

Change the project location ↑

Hillingdon / project questions

Is a Neutral result the whole Hillingdon assessment?

No. The policy also addresses exposure, mitigation and improving air quality.

How would ACP scope a generator scheme?

We would examine emissions, operating patterns, discharge geometry, nearby buildings and sensitive receptors, alongside the applicable planning requirements.

The assessment & your commission

Do I need an air quality assessment for planning?

The need depends on the proposal, location and local requirements. Relevant considerations include new exposure near pollution sources, development-generated emissions, construction activity and sensitive uses. Send the council’s request or your proposal details so we can identify the appropriate assessment route.

Which pollutants does an assessment consider?

For road-related planning work, nitrogen dioxide (NO₂) and particulate matter, including PM₁₀ and PM₂.₅, are common considerations. Other sources can introduce different pollutants. The scope should identify the relevant pollutants and assessment criteria, rather than assume one list suits every development.

Is the assessment desktop-based, or will you visit?

Some projects can use existing data and drawings. Others need a site visit, additional monitoring or detailed modelling. Monitoring measures conditions during a particular period; modelling can examine scenarios that have not yet occurred. We select the approach to answer the planning question.

How much does an air quality assessment cost?

The fee depends on the assessment route, site complexity, data availability and required outputs. A screening report, detailed dispersion model and monitoring programme are different commissions. Your quotation will define the scope, information needed and any separately priced options.

How long will the work take?

We agree a programme around the submission date and the inputs required. Drawings, traffic data and plant information can affect delivery. Where monitoring is needed, the survey period must be suitable for its purpose. Send your deadline with the brief so we can plan the work properly.

Can you coordinate air quality with noise and other assessments?

Yes. ACP’s environmental services allow air quality questions to be considered alongside noise, odour and ecology requirements. This is particularly useful where ventilation, plant, construction activity or sensitive receptors create overlapping design decisions.

What should I send for a quotation?

Start with the enquiry form: site address or postcode, a short project description and your deadline. Mention any council correspondence or existing application. Your consultant will then request relevant documents, drawings and technical inputs to prepare the scoped quotation.

Already have a planning condition or an officer’s request? Mention it in the form; your consultant will request the document after reviewing your enquiry.

Get a scoped quotation →

YOUR BRIEF / A CLEAR FEE PROPOSAL

Tell us about the site.
We’ll define the right scope.

Start with the form, even if you are not sure which assessment you need. A consultant will review your enquiry and get in touch to clarify the project.

  1. Share the essentialsTell us the site location, proposal and any deadline. Select several assessment types if your project needs a combined response.
  2. We request the right documentsAfter you enquire, we’ll ask for the information needed to scope the work. This may include council consultation comments, a planning reference or decision notice, site plans, drawings and the proposed use.
  3. Receive a scoped quotationOnce the necessary information is available, we’ll aim to provide your fee proposal promptly, setting out the assessment scope, deliverables, assumptions and programme.

Prefer to discuss the project? 0330 236 7329

YOUR PROJECT / OUR NEXT STEP

Discuss your Hillingdon project

Tell us the site location and proposal. Choose any relevant assessment types, or describe a combined or unfamiliar requirement in your own words.

What do you need? (optional — choose any that apply)

Choose more than one service, or simply describe your requirements in the project brief. You do not need to know the technical name.

Choose assessment types
Planning and development
Dust and monitoring
Habitats and ecological receptors
Plant, processes and odour
London-specific submissions
Other or combined requirements

We will confirm the scope and delivery arrangements for specialist requests before quoting. Selecting a service does not commit you to it.

We use your details to respond to your enquiry. Privacy policy.

Have documents ready?

Keep your planning correspondence and latest drawings to hand. Your consultant will explain how to send them with the enquiry reference, so the brief and supporting information stay together.

For plant or industrial projects, we may also request equipment data, emissions, operating hours and stack details. For ecological work, relevant habitat surveys and the ecologist’s brief are useful.

No need to gather everything before enquiring.

Technical references & further reading

Technical framework checked on 20 October 2026. The assessment scope uses the guidance and policy applicable to the particular proposal.

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