The Square Mile / Planning & development
Air quality assessment in the City of London
Connect the Square Mile’s monitoring evidence with your building, plant and public-realm design. ACP provides air quality assessment, monitoring and mitigation advice for office developments, refurbishments, mixed-use schemes and construction projects.
Resolve intakes, generators, servicing and roof terraces early in the assessment brief.
Discuss your projectCity-specific evidence
Local Plan DM15.6, validation and the SPD transition.
Street to rooftop
Traffic, plant, exposure and construction in a dense urban setting.
A coordinated brief
Organise the assessment and design inputs with the evidence planner.
01 / Local context
A compact area with distinct exposure settings
Bank, Cannon Street and Thames Street
Study street-level exposure, junction activity, servicing and the routes people use. The 2025 monitoring record retains local contrasts around Cannon Street and Upper Thames Street; use actual site evidence rather than assuming one Square Mile background.
Barbican, Beech Street and Farringdon
Keep residential, school and workplace receptors visible alongside the traffic setting. Compare Beech Street roadside measurements with urban-background evidence, accounting for street geometry and the location of ventilation openings.
City Cluster and elevated amenity
Fenchurch Street, Bishopsgate and surrounding towers bring intakes, neighbouring roofs and publicly accessible terraces into the brief. Consider flues, standby generation and downwash where relevant to the actual proposal.
The City’s AQMA remains designated
Defra’s AQMA record covers the entire Square Mile: declared 26 January 2001 for annual and one-hour NO₂ and daily PM₁₀. A declaration, a monitor result and a proposed development’s effect answer different questions.
The City’s Air Quality Strategy 2025–2030 addresses sources including commercial heat and power and construction. For the wider planning framework, see our London air quality guide.
02 / Monitoring and trends
Read the trend alongside the setting
The 2025 Annual Status Report was published in May 2026. Beech Street NO₂ fell from 36.5 to 32.9 µg/m³ between 2024 and 2025; the Aldgate School background station rose from 20.1 to 21.6. Neither movement should be transferred automatically to a different street or development.
2019–2025 / Annual mean NO₂ / µg/m³
Roadside and background histories
The same year can show different movements at different sites.
Beech Street
CT4 / Roadside
32.9 µg/m³ in 2025
The Aldgate School
CT3 / Urban background
21.6 µg/m³ in 2025
Read the annual values
| Year | Beech Street | Aldgate School |
|---|---|---|
| 2019 | 62 | 33 |
| 2020 | 29 | 22 |
| 2021 | 31 | 23 |
| 2022 | 40.6 | 22.8 |
| 2023 | 36.1 | 21.5 |
| 2024 | 36.5 | 20.1 |
| 2025 | 32.9 | 21.6 |
Source: 2025 ASR, Table G. Calendar-year NO₂ capture: Beech Street 99.6%; Aldgate School 98.2%. This chart describes observations and does not attribute the change to a single intervention.
03 / Pollutants and network coverage
Look beyond a single NO₂ figure
The network covers five continuous monitoring locations, including ozone at Guildhall. Pollutant coverage differs by site; several instruments at one location are not separate stations.
| Monitoring location | NO₂ | PM₁₀ | PM₂.₅ |
|---|---|---|---|
| Farringdon Street CT2 | 33.7* | — | 10.0 |
| Aldgate School CT3 | 21.6 | 17.7 | 10.2 |
| Beech Street CT4 | 32.9 | 17.5 | — |
| Bell Wharf Lane CTA | 27.8 | 19.4 | — |
*Farringdon Street NO₂ was annualised from 66.0% calendar-year capture following installation in May 2025. The other displayed annual measurements had at least 92% capture. A dash indicates no annual value in the corresponding table.
Diffusion tubes reveal street-level contrasts
The ASR reports NO₂ monitoring at 83 locations overall, including automatic instruments and passive networks. Two tube locations exceeded the annual objective: Cannon Street Bank 1, 42.0 µg/m³, and Walbrook Wharf WW, 45.1 µg/m³. Bank 1 was annualised from 38.5% capture; WW had 100% capture.
Particles, ozone and benzene
PM10 rose at all three reporting sites in 2025; both PM2.5 sites also rose. Guildhall monitors ozone, while benzene sampling began at Farringdon Street in 2025. Match the pollutant and averaging period to the assessment question.
Background and receptor are distinct
The ASR explains that simple single-road NO₂ fall-off corrections were not applied in the City’s complex urban setting. Select representative background and receptor inputs. Defra’s local-authority dashboard and the City monitoring network provide complementary context.
04 / Planning requirements
Build a City-specific submission schedule
Local Plan 2015: DM15.6
The adopted Local Plan addresses development impacts, combustion technology, construction emissions, intake location and flue discharge. Establish the actual plant and exposure pathways before deciding the depth of an Air Quality Impact Assessment.
Air Quality SPD: adoption and implementation
The City’s current planning page says the revised SPD was adopted on 22 June 2026, with full implementation tied to City Plan adoption. It retains the 2017 SPD and encourages developers to review the 2026 guidance. Record the applicable position when submitting.
Validation and distinct submissions
Use the current application forms and validation gateway alongside the City’s air-quality checklist. Keep AQIA, Air Quality Neutral and any Air Quality Positive statement distinct. For applicable EIA development, the City requests an Air Quality Positive approach.
Sustainability, construction and NRMM
Coordinate the Planning for Sustainability SPD with the City construction guidance and current NRMM requirements. Older linked documents may retain earlier London policy or engine-standard references; check the current requirement rather than copying an historic threshold.
05 / Assessment and design
Connect the evidence to practical decisions
Plant and servicing
Collect boiler, generator, kitchen-extract and vehicle information. Distinguish routine operation, testing and emergency use. Check whether modelling or an environmental-permitting workstream is relevant to the actual plant.
Street, façade and rooftop
Locate occupied floors, air intakes, neighbouring windows, public spaces and roof terraces. Consider surrounding buildings and flue dispersion; a street-level annual mean alone cannot resolve every rooftop question.
Construction and deconstruction
Agree the dust and machinery-emissions scope, sensitive neighbours, protective works and monitoring response. Coordinate acoustics, logistics and phasing so the construction documents describe the same activities.
For linked workstreams, explore our noise assessment advice, odour assessment service and London assessment tools.
06 / Public planning example
How local planning records translate into a brief
130 Fenchurch Street: generators and roof-level design
The officer report dated 30 September 2025 for 25/00529/FULEIA assessed demolition, construction and operation. It described an electric building with life-safety diesel generation and an Air Quality Positive submission. Proposed conditions addressed landlord and future tenant generators, NRMM registration and flues positioned away from intakes and accessible roof spaces.
For another City scheme, the useful lesson is to assess retained combustion and future tenant plant alongside the main building strategy.
Public officer report, paragraphs 828–835 and proposed conditions 62–65. This is a dated officer recommendation and proposed control package; it does not establish completion or measured performance.
Plan the evidence before plant locations are fixed
Record equipment duty, fuel, test regime, flue geometry and nearby receptors. Keep the air-quality scope coordinated with structural, mechanical, fire-safety and acoustic design. A later tenant installation may need its own assessment and condition response.
The appropriate assessment depends on the site and the actual proposal.
07 / Interactive project checklist
City of London evidence planner
Answer five questions to build a starting brief. Select “Not sure yet” for missing information; unresolved points stay visible in your results. Answers are processed on this page.
The planner organises a project brief. It does not determine legal requirements or demonstrate compliance.
08 / Emerging requirements
Keep the policy and data dates visible
City Plan 2040: verify the adoption position
The examination documents page published the Inspectors’ Report and main modifications on 13 October 2026. Publication of an examination report is distinct from formal plan adoption. Recheck the adoption notice and the revised SPD implementation position at submission.
The City’s Air Quality Strategy covers 2025–2030. Its ASR describes planned monitoring upgrades, including additional Beech Street PM₂.₅ monitoring in 2026. Keep the measured 2025 evidence separate from later equipment changes and provisional live data.
Emerging requirements can affect plant, emission mitigation, exposure and construction design. Record the edition and status of each source in the assessment brief.
09 / Your next step
Start your City air quality brief
Send the address, proposal, plans and application stage. Include plant schedules, servicing information, ventilation and roof-terrace drawings, any existing assessment and the City’s written request.
ACP can identify the relevant assessment workstreams, evidence gaps and next design decisions.
Discuss the assessment scope10 / Common questions
City of London air-quality FAQs
Does this page cover the Square Mile or all of London?
This page concerns the City of London Corporation planning area: the Square Mile. Westminster, Tower Hamlets and other London authorities have different local policies and evidence requirements. Use the London hub for the wider framework and the relevant authority page for the site.
Is the whole City of London an Air Quality Management Area?
Yes. Defra lists the whole City AQMA, declared on 26 January 2001 for annual and one-hour nitrogen dioxide and 24-hour PM10. The designation remains listed. It is distinct from a statement about whether every monitoring location currently exceeds an objective.
Which City air-quality SPD should an application use?
The City says its revised SPD was adopted on 22 June 2026, with full implementation in decision-making tied to City Plan adoption. Its current planning page also retains the 2017 SPD. Check the application date, adopted development plan and latest implementation notice when agreeing the scope.
Why are standby generators important in City assessments?
A largely electric office can still contain combustion equipment for emergency power. Review generator alternatives, fuel, emissions, testing and flue discharge alongside nearby intakes, roof terraces and surrounding buildings. A low annual operating time does not remove the need to consider short-term effects.
Does the City monitor air quality with diffusion tubes?
Yes. The 2025 ASR reports diffusion-tube networks covering long-term sites, the Bank area, transport-strategy locations and other City sites. The report states that NO2 was monitored at 83 locations overall. This total includes automatic monitoring and must not be described as 83 physical tubes.
Can I use a roadside reading as my office or roof-terrace background?
Select monitoring evidence by pollutant, year, height, road influence and the assessment purpose. A kerbside concentration is not automatically representative of a set-back intake or roof terrace. Buildings, multiple roads and nearby flues may require a more detailed assessment.
Is Air Quality Neutral the same as Air Quality Positive?
Air Quality Neutral compares building and transport emissions with the applicable benchmarks. Air Quality Positive records design measures that improve the air-quality outcome. Exposure, local effects, construction dust and combustion dispersion remain separate questions within the assessment scope.
What should a City construction dust brief include?
Consider demolition, earthworks, construction, trackout, neighbouring occupiers and the public realm. Align the assessment with the City Code of Practice, protective works, the current NRMM requirements and any planning conditions. Define monitoring and response arrangements where proportionate.
City of London / 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.
Evidence / Checked 20 October 2026
City of London guidance and sources
Monitoring results refer to 2025; planning and document status are dated separately.
- 2025 Annual Status Report
- Annual report library
- City monitoring network
- Defra City AQMA record
- Local Plan 2015
- Planning and air quality checklist
- Revised Air Quality SPD 2026
- Application forms and validation checklists
- Sustainability planning requirements
- City Plan 2040 examination documents
- City construction guidance
- Current NRMM requirements
- Air Quality Strategy 2025–2030
- 130 Fenchurch Street officer report
- Defra local-authority dashboard