Air Quality Neutral Assessment

An air quality neutral assessment is a requirement for planning applications in London. For planners, developers, and architects, understanding what it involves, and how it aligns with the London Plan is essential for avoiding delays and securing consent in planning applications.

This article explains air quality neutral assessments in a clear, practical way. It covers guidance, benchmarks, costs, reporting requirements, and how air quality neutral differs from air quality positive.

Below is a flowchart produced to illustrate the air quality neutral decision process.

What is an Air Quality Neutral Assessment?

An air quality neutral assessment evaluates whether a proposed development will result in no net increase in air pollutant emissions compared to defined benchmarks.

The policy was introduced to mitigate the cumulative impacts of developments in London, where individual schemes can appear insignificant but collectively contribute to worsening local air quality.

Air quality neutral assessments focuses on pollutants NOx and PM2.5 and provides benchmarks for two emission sources:

• Building-related emissions (from energy use and heating systems); and

• Transport-related emissions (from vehicle trips and parking associated with the development).

If emissions are at or below the relevant air quality neutral benchmarks, the development is considered air quality neutral. This does not mean zero emissions, but rather that emissions are controlled to a policy-defined acceptable level.

Air Quality Neutral Guidance

The air quality neutral guidance produced by the Greater London Authority (GLA) replaces previous guidance published in 2014 as part of the GLA sustainable design and construction supplementary planning guidance.  

Most notable updates in the guidance include the replacement of PM10 with PM2.5, reflecting stronger public health evidence. For building emissions, the PM2.5 benchmark is effectively zero, meaning biomass boilers or on-site combustion plants are unlikely to be air quality neutral unless it is part of an emergency or life-saving backup plant.

When is an air quality neutral assessment required?

Policy SI 1 of the London Plan states that all development proposals in London must be at least Air Quality Neutral. Outside London, air quality neutral principles are increasingly referenced in local planning policy, although requirements are less standardised.

The Air Quality Neutral London Plan Guidance (LPG) sets out how developers should demonstrate compliance with Policy SI1 and how benchmarks for NOx and PM2.5 should be applied.

Air Quality Positive

While air quality neutral aims for no net increase in emissions, air quality positive goes a step further. An air quality positive assessment demonstrates that a development actively reduces emissions compared to the existing or baseline scenario.

Air quality positive approaches may include:

• Zero emission heating systems such as Air Source Heat Pumps (ASHP)

• Car-free or zero parking provision

• Active travel and public transport enhancements

Air quality positive requirements are still emerging but are increasingly encouraged on strategic or high-profile schemes. An overview of air quality positive and air neutral guidance can be seen in the video below.

Air Quality Positive and Air Quality Neutral Guidance Brief

Simplified vs Detailed Air Quality Neutral Assessment

The Air Quality Neutral London Plan Guidance (LPG) introduces a clearer distinction between simplified and detailed air quality neutral assessments, allowing developments with negligible emissions to demonstrate compliance without undertaking full calculations.

Simplified Air Quality Neutral Assessment

The simplified procedure applies to minor developments or major developments that do not include any additional emissions sources.

For building emissions, a simplified approach may be used where the development:

• Proposes zero-emission heating, such as air source heat pumps; or

• Uses ultra-low NOx gas boilers (≤40 mg/kWh); or

• Connects to an existing heat network.

For transport emissions, a simplified procedure may be appropriate where:

• The development is classified as car-free; or

• Parking provision does not exceed the London Plan maximum parking standards (Policies T6 and T6.1–T6.5).

  
  

In some circumstances, such as when a site is located within an Air Quality Focus Area, the local planning authority may require a full air quality neutral assessment for a minor development.

Full (Detailed) Air Quality Neutral Assessment

A full air quality neutral assessment is required when major developments contains additional emission sources or when criteria for the simplified procedure has not been met.

Calculating building emissions involves using the proposed heating system and expected energy demand to estimate annual emissions. Transport emissions are assessed by calculating vehicle trips generated by the development, typically using results provided by a transport assessment.

For phased developments, the guidance requires that each phase, as well as the development as a whole, is considered air quality neutral.

What to do if your development is Not Air Quality Neutral?

If an air quality neutral assessment shows that benchmarks are exceeded, the guidance sets out a clear policy hierarchy for addressing non-compliance.

The first step is to explore design changes to reduce emissions at the source. For transport-related exceedances, this may include reducing parking provision to comply with maximum parking standards. For building-related emissions, this could involve switching to zero-emission heating systems, such as ASHP.

Where design changes are not feasible, the next option is to agree on mitigation measures with the local planning authority. This may include electric vehicle charging provision, improved cycle infrastructure, or mechanical ventilation.

If design changes or mitigation measures cannot be agreed, emission offsetting payments should be considered as a last resort. This decision is subject to the discretion of the local planning authority. The guidance makes clear that offsetting is not a substitute for good design, and reducing emissions through design and mitigation is always the preferred approach.

What should Air Quality Neutral Assessment reports include?

Simplified Procedure

Reports should include an air quality neutral statement, supported by summary tables confirming:

• Proposed heating technology and emission performance

• Parking provision compared against London Plan maximum standards

• Confirmation that simplified air quality neutral criteria are met

• Clear references to supporting planning documents

Full Procedure

The air quality neutral assessment should be a clearly defined section within the wider air quality assessment and include:

• Tables calculating the Building Emission Benchmark (BEB) and Transport Emission Benchmark (TEB)

• Tables showing predicted building and transport emissions

• A clear statement on whether the development meets air quality neutral benchmarks

• Details of design changes or on-site mitigation where benchmarks are exceeded

• Supporting evidence and document cross-references

• Clear referencing of inputs such as GIA, parking numbers, and heating systems

• All emission factors, trip rates, and assumptions clearly stated

• Manufacturer data provided where specific plant or boilers are assumed

Air Quality Neutral Assessment Cost

Air quality consultants typically charge extra for this service. However, Air Quality Solutions provide air quality neutral assessments at no additional cost when included within an air quality assessment package.

What companies provide Air Quality Neutral Assessment services?

Several consultancies provide this service, including:

• Specialist air quality consultants, like Air Quality Solutions, can help you complete your air quality neutral assessments; and

• Large multidisciplinary consultancies.

  
  

Which consultancies specialise in air quality neutral assessments?

Consultancies that regularly operate in London and engage with GLA policy are best placed to deliver compliant air quality neutral assessments. Look for teams with direct experience of providing air quality neutral assessments for a range of projects.

Relationship to Air Quality Assessments

An air quality neutral assessment does not replace a full air quality assessment. Instead, it complements:

• Baseline air quality assessments

• Standard air quality assessments

• Impact air quality assessments

For a full overview, see our detailed guide on air quality assessments for planning.

Air Quality Neutral Summary

An air quality neutral assessment is a critical component of planning in London and a requirement of Policy SI 1 in the London Plan. By understanding GLA air quality neutral guidance, planners, developers, and architects can avoid delays and design compliant, future-proof developments.

Early engagement with experienced air quality consultants ensures assessments are proportionate, policy-compliant, and smoothly integrated into the planning process.