The newly published Air Quality Neutral Guidance – what does it mean?

Air Quality Neutral assessments require a comparison of building and transport emissions with benchmarks. Last year, the RPS Group wrote about the Greater London Authority (GLA)’s new draft Air Quality Neutral Guidance, replacing its original guidance from 2014.

The final version of the new guidance has now been published, and Fiona Prismall, Technical Director for Air Quality at RPS, looks at the differences between the new Air Quality Neutral Guidance and its 2014 predecessor, with particular interest in how these changes affect prospects for developers in London.

The new approach

The GLA’s new Air Quality Neutral guidance applies to all developments in London. Previous guidance only applied to major developments, meaning relatively small development applications now have the potential to become more complicated.

For developers, the good news is that only a ‘simple’ assessment is required for those developments with little or no emissions into the air. This includes developments that use efficient boilers, air or ground source heat pumps, and developments that do not exceed the maximum parking standards set out in the London Plan.

What are the key changes?

The earlier guidance provided benchmarks for two air pollutants: nitrogen oxides (NOx) and PM10 (particulate matter up to 10 µm in diameter, which remains suspended in the air for long periods and is small enough to be breathed in). One of the key differences is that the new guidance provides benchmarks for NOx and PM2.5 (particulate matter up to 2.5 µm in diameter which can pass through the air-blood barrier). Our previous article discusses London’s policy on particulate matter.

For building emissions, the new guidance sets a PM2.5 benchmark of zero. This change means that developments with a biomass boiler or on-site plant fuelled by diesel are unlikely to be air quality neutral as there’s a high chance these appliances will emit particles. The caveat to this is a backup plant for emergency and lifesaving power are to be excluded from the development’s emissions.

Where the development does not qualify for a ‘simple’ assessment, a ‘detailed’ assessment is required. For major developments, another difference sees the new guidance require each phase of the development, as well as the development as a whole, to be air quality neutral. The implications of this remain to be seen, but at the very least we know that the assessment itself will be more complex.

The results

If the results of a ‘detailed’ assessment indicate the benchmarks are exceeded, the development is deemed not air quality neutral. It will then need to be modified to try and meet the benchmarks. If they still can’t be met after modification, the next step would be to seek agreement with the local planning authority to secure mitigation measures to reduce emissions or concentrations.

As a last resort, it may be possible to agree an offsetting payment with the local authority. This involves a calculation of the annual monetary value of emissions above the benchmark (the ‘excess emissions’) to offset the impacts. The total offsetting payment is calculated as the total monetary value over a 30-year period. In our experience, this can add up to a substantial amount. The guidance makes it clear that offsetting should be the exception and modifying the development to meet the benchmarks is the most preferable solution.

It’s advisable to engage with air quality professionals at an early stage so that air quality neutrality is considered in advance of the development’s design.

For more information on the guidance or to discuss development assessments with an RPS expert, please contact Fiona Prismall at:



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