Air quality assessment authors and IAQM expectations

There is no statutory licence for an air quality assessment author. Planning law does not name a qualification, so the question a case officer and an environmental health officer are really asking is whether the work follows the methods the Institute of Air Quality Management sets out and whether the person who did it can defend the assumptions. That is what competence means here, and it is why an assessment written to the right structure by the wrong person still gets sent back.

Two distinct bodies of method sit inside most reports, and plenty of authors are strong on one and weak on the other.

What an assessment has to cover before anyone accepts it

An Air Quality Assessment submitted with a planning application normally has to answer four questions. Does the development expose new receptors to poor air quality. Does it worsen conditions for existing receptors. What happens during construction. And what mitigation is proposed, tied to a condition or an obligation.

The screening decision comes first, and it is where weak reports fail. IAQM and Environmental Protection UK guidance sets out indicative criteria for when an assessment is needed, based on traffic generation, the presence of an Air Quality Management Area, and whether the scheme introduces new combustion plant. An author who screens out a scheme without setting out the traffic figures and the receptor distances has given the officer nothing to check.

Where a site sits in or near an AQMA declared under Part IV of the Environment Act 1995, assume the council will want the full assessment regardless of what screening says. Councils declare those areas because they are already failing an objective, and the annual mean nitrogen dioxide objective of 40 micrograms per cubic metre in the Air Quality Standards Regulations 2010 is the number everything gets measured against.

Modelling competence and verification

Dispersion modelling is a specialist skill. The model itself is not the hard part. Building a defensible input set is.

Ask about four things when you appoint someone. Which model they are using and why it suits the source type, whether road traffic, industrial stack or car park ventilation. How they derived traffic inputs, and whether those match the transport evidence submitted with the same application. What meteorological data they used, from which station, over how many years. And how they verified the model against local monitoring.

Verification is the step that separates a usable report from a plausible one. Modelled concentrations are compared against measured data from the council's diffusion tubes or automatic monitors, and an adjustment factor is derived and applied. A report that presents modelled results with no verification section, or that verifies against a monitor five kilometres away in a different street canyon, will be challenged by any environmental health officer who reads it properly. Ask to see the verification calculation, not a sentence saying it was carried out.

One honest uncertainty: verification factors can move considerably depending on which monitors are chosen, and two competent consultants can land on different adjustments for the same site. That is a reason to show the working, not to hide it.

Construction dust is a separate discipline

The IAQM construction dust method is qualitative and risk-based, and it has nothing to do with dispersion modelling. It classifies the site by the scale of demolition, earthworks, construction and trackout activity, sets the sensitivity of the surrounding area by receptor distance and count, combines the two into a risk category, and then prescribes mitigation proportionate to that category.

Done properly, the conclusion is that residual effects are not significant once the mitigation is secured. That mitigation belongs in the Construction Management Plan rather than sitting orphaned in the air quality report, and the two documents should say the same thing. They frequently do not, because they were written by different people three weeks apart.

An author who is a modeller by background sometimes treats the dust chapter as boilerplate. Read it. If the receptor counts do not match the site's actual surroundings, the risk category is wrong and so is the mitigation.

The data sources the author should be using

There is a standard evidence set for England, and its absence tells you something.

• Defra background concentration maps for the relevant year and grid square
• The Emissions Factors Toolkit for road vehicle emission rates, at the current version
• The council's own Annual Status Report and monitoring data, which is published and free
• Defra Local Air Quality Management technical guidance for method and verification
• Damage cost figures where a mitigation contribution is being calculated

Two details catch people out. Background maps are projected forward by year, so the report must state the assessment year and use the matching data set. And the Emissions Factors Toolkit is updated periodically, which means a report recycled from a project two years earlier can carry emission factors that no longer match the version the council uses.

Reading an assessment before it goes in

Check the arithmetic chain rather than the prose. Traffic figures in the air quality report should reconcile with the Transport Assessment or transport statement, including the assessment year and the growth factors. Receptor locations should be at the height and position of real windows and gardens, not at a convenient point on a boundary.

Then look for the assumptions that were quietly made. A biomass boiler removed from the scheme after the report was written. A car park ventilation stack modelled at a height that does not appear on the elevations. An assumption that all deliveries arrive outside peak hours, with no condition proposed to secure it. Each of those is a reason for the council to ask for a revised assessment after validation, which costs weeks.

Where mitigation is proposed, it needs to be capable of being conditioned. Electric vehicle charging provision, low emission boiler specifications, delivery management and travel plan measures all work as conditions. Vague commitments to best endeavours do not.

Where environmental health pushes back

Environmental health officers, not planning officers, tend to be the technical readers. The objections that recur are predictable.

Insufficient verification. Receptors placed to flatter the result. Construction dust mitigation that is generic rather than specific to the site risk category. Failure to consider odour or plant noise where the same development introduces kitchen extract or standby generators. And mitigation that is described but not translated into a condition the council can enforce.

If a scheme also generates a mitigation contribution, expect the damage cost method to be used, and expect the officer to want the calculation shown. Councils increasingly publish their own air quality supplementary planning documents with local expectations that sit on top of national guidance, so read the local document before commissioning the work.

Membership of the IAQM signals engagement with the method and its updates, and it is a reasonable thing to ask about, though it is not a statutory requirement and no council can demand it as a validation condition. What a council can do is decline to accept an assessment it regards as methodologically inadequate. For a report of this kind, professional review is strongly advised, and PlanScope's professional directory is one route to a reviewer who can check the method before submission.

For specialist technical reports, qualified professional input may be required. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.