If you’re planning a development anywhere in Greater London, there’s one requirement you can’t skip: your scheme must be air quality neutral. Get it wrong, and your planning application can be delayed or refused. Get it right, and it’s usually a straightforward part of your submission.

This guide explains exactly what air quality neutral means, how the benchmarks work, what a full assessment involves, and the mistakes that catch developers out. We’ve kept it plain and practical, with a worked example and a real project to show you how it plays out.

What is air quality neutral?

Air quality neutral means your development won’t add more pollution to London’s air than a set benchmark allows. It doesn’t mean zero emissions. It means your building and transport emissions stay at or below the levels the Greater London Authority (GLA) has defined as acceptable for your type and size of development.

The policy comes from Policy SI1 of the London Plan. It was brought in because lots of small developments, each adding a little pollution, were quietly making London’s air worse over time. Every scheme individually looked harmless, but together they added up. Air quality neutral tackles that by putting a cap on each new development.

The rule is simple: every development proposal in Greater London must be at least air quality neutral, or risk refusal.

Which pollutants and emission sources are assessed?

An air quality neutral assessment looks at two pollutants: nitrogen oxides (NOx) and fine particulate matter (PM2.5). The older 2014 guidance used PM10, but the current guidance switched to PM2.5 because the health evidence around fine particles is much stronger.

Your emissions are measured against two benchmarks:

• The Building Emissions Benchmark (BEB) — emissions from your heating and energy systems, such as gas boilers, CHP plant, or backup generators.
• The Transport Emissions Benchmark (TEB) — emissions from the vehicle trips your development generates.

Your proposal has to meet both benchmarks. Passing one but failing the other means your scheme is not air quality neutral.

How the benchmarks work

The benchmark you’re measured against depends on what you’re building and where.

For building emissions, the allowance depends on your land use (residential, office, retail, industrial) and your heating system. Here’s the key point that shapes most modern schemes: a development using 100% electric heating, such as air source heat pumps, produces no on-site NOx and automatically meets the Building Emissions Benchmark. For PM2.5, the building benchmark is effectively zero, which means biomass boilers and most on site combustion plant will not pass unless they’re genuine emergency backup.

For transport emissions, the allowance depends on your land use and your location the Central Activities Zone, Inner London, and Outer London all have different trip rate benchmarks. Central London has better public transport, so lower car trip rates are expected there.

Simplified vs full assessment: which do you need?

Not every development needs a full set of calculations. The guidance splits assessments into two routes.

Feature	Simplified Procedure	Full (Detailed) Procedure
Applies to	Minor developments, and major developments with no additional emission sources	All major developments, and any scheme that fails the simplified criteria
Building emissions	Passes if heating is a heat pump/zero-emission source, an ultra-low NOx boiler (≤40 mg/kWh), or connects to an existing heat network	Full BEB calculation using heating system and expected energy demand
Transport emissions	Passes if car-free, or parking is within London Plan maximum standards (Policies T6–T6.5)	Full TEB calculation using predicted vehicle trips from a transport assessment
Report output	Short air quality neutral statement with summary tables	Detailed section within the wider air quality assessment, with full calculations
Consultant needed?	Often not essential, but recommended	Yes — specialist input strongly advised

One important catch: if your site sits inside an Air Quality Focus Area a part of London with especially poor air quality your local planning authority can insist on a full assessment even for a minor development.

A worked example (so you can see how it adds up)

Let’s take a simple case. Imagine a small residential block in Inner London.

The consultant calculates the Building Emissions Benchmark for the scheme’s floor area say the total BEB comes out at 161.7 kg of NOx per year. The proposed development, using an efficient low-NOx boiler system, produces 84 kg of NOx per year. Because 84 kg is comfortably below the 161.7 kg benchmark, the development passes for building emissions and is air quality neutral on that measure.

The same scheme is then tested for transport. If the predicted car trips generate emissions above the Transport Emissions Benchmark, the scheme fails on transport even though it passed on buildings. At that point the design has to change, usually by cutting parking spaces, before it can be called air quality neutral.

This is the trap most developers miss: you have to pass both, and transport is where schemes usually fall down.

What happens if your development is not air quality neutral?

If your assessment shows you’re over a benchmark, the guidance sets out a clear order of steps and offsetting money is genuinely the last resort.

1. Change the design first. Switch to zero emission heating like an air source heat pump, or reduce parking to bring transport emissions down. This is always the preferred route.
2. Agree mitigation with the local authority. If design changes aren’t enough, you might add electric vehicle charging, better cycle facilities, or improved ventilation.
3. Offsetting payment as a last resort. If nothing else works, you can agree a payment with the borough. This is calculated as the monetary value of your excess emissions over a 30-year period, using DEFRA’s damage cost figures for NO2 and PM2.5. In our experience this can be a very large sum which is exactly why fixing the design early is so much cheaper.

Air quality neutral vs air quality positive: what’s the difference?

These two terms get mixed up constantly, so here’s the plain version.

Air quality neutral London plan means no net increase in emissions above the benchmark. Air quality positive goes further it means your development actively improves air quality compared to the baseline. Air quality positive is currently expected mainly on large, strategic masterplan schemes, and it usually involves things like fully zero emission heating, car free layouts, and strong active travel provision. For most developments, air quality neutral is the requirement you need to meet.

A real project example

We recently supported a mid sized residential scheme in an Inner London borough that had failed its first air quality neutral check on transport emissions. The original design included too much car parking for its location.

Rather than heading straight for an expensive offsetting payment, we reworked the transport inputs, reduced the parking allocation to within London Plan standards, and confirmed the all electric heating already met the building benchmark. The revised assessment passed on both counts, and the borough accepted it without conditions. The developer avoided a five-figure offsetting payment and kept the application on programme.

That’s the value of getting air quality neutral looked at early the fix at design stage cost a fraction of the alternative.

Common mistakes to avoid

• Leaving transport until last. Building emissions are easy to solve with electric heating. Transport is where most schemes fail. Model it early.
• Assuming minor = exempt. A minor development inside an Air Quality Focus Area can still be pushed to a full assessment.
• Forgetting phased schemes. For phased developments, each phase and the whole development must be air quality neutral. Passing overall isn’t enough.
• Specifying gas boilers by habit. With the PM2.5 building benchmark effectively at zero and NOx limits tight, combustion heating is increasingly hard to justify. All-electric is the safe route.
• Submitting without manufacturer data. If you assume a specific low-NOx boiler, you need the manufacturer’s data sheet to back it up, or the assessment won’t hold.

How FreshBreeze can help

We prepare air quality neutral assessments for developments across London, from simplified statements for minor schemes to full BEB and TEB calculations for major applications. If you’re not sure which route your project needs, we’ll tell you before you commit to anything. Learn more about our air quality assessment services or get a quote for your London development.

Conclusion

Air quality neutral is a firm requirement for every development in Greater London, but it doesn’t have to slow your project down. The schemes that pass smoothly are the ones that consider it early — choosing electric heating, keeping parking within London Plan standards, and modelling transport emissions before the design is locked in. Leave it too late and you risk redesign, delay, or a costly offsetting payment. Bring it in at the start and it becomes a simple box to tick on the way to planning consent.