Air quality consultant competence and what IAQM signals

Air quality assessment has no statutory competent person, so the question of who should write one is answered by method rather than by licence. The Institute of Air Quality Management publishes the guidance the profession works to, and its membership grades are the clearest signal of assessed experience available. What separates a defensible assessment from a weak one, though, is usually not the letters after the author's name. It is whether the model was verified against local monitoring, and whether the report says so.

What an air quality assessment involves

Two phases, assessed differently.

Construction is assessed for dust and for the emissions of construction traffic. The IAQM method for demolition and construction categorises the site by the scale of each activity and by the sensitivity of the surrounding area, producing a risk category that drives the mitigation package. The output is not a set of concentrations but a schedule of measures, which is why it ends up secured through a Construction Management Plan rather than through an air quality condition.

Operation is assessed for the pollutants that matter in planning, principally nitrogen dioxide and particulate matter, at existing and proposed receptors. Where the change in traffic is small, a screening assessment against the published criteria may be enough. Where it is larger, or where the site sits in an air quality management area declared under Part IV of the Environment Act 1995, dispersion modelling is expected.

There is a third strand on larger schemes: whether the development itself exposes new occupants to poor air quality, which is a question about the design of the building rather than about its traffic.

Professional membership and the guidance behind it

Membership of the Institute of Air Quality Management at Member or Fellow grade indicates experience that has been assessed by peers. Associate grade indicates a route in progress. Chartered environmentalist status through the wider environmental profession is a complementary signal.

More useful than the grade is whether the author works to the published guidance, and whether they can say which parts of it they applied. The relevant documents are the IAQM construction dust guidance, the joint planning guidance produced with Environmental Protection UK on air quality in development control, and the national technical guidance on local air quality management published by Defra.

Ask which version of each they are using. Technical guidance and emission factor tools are updated, and an assessment run on a superseded emissions toolkit will be picked up by an environmental health officer who runs the current one.

Modelling, monitoring and verification

This is the part that decides whether the assessment survives review.

A dispersion model predicts concentrations from traffic and other sources. It will be wrong to some degree, because the inputs, the meteorology and the model itself carry uncertainty. Verification is the process of comparing modelled results against measured concentrations at local monitoring sites and deriving an adjustment factor to apply to the results.

An assessment without verification is an assertion. An assessment with verification against a single distant monitoring site, in a different street type, is barely better. What you want to see is verification against local data, an explanation of the sites used, the adjustment factor derived, and a comment on how well the model performed.

Where traffic data is the weak point, the same figures should come from the Transport Assessment rather than from a separate exercise. Two documents in the same submission giving different traffic flows is a problem that officers notice immediately.

How environmental health reviews the work

The council's environmental health team, rather than the planning case officer, usually reviews the assessment. They run the same tools and they know the local monitoring network better than any consultant does.

Their review tends to follow a fixed path: is the scoping justified, are the receptors sensible, is the background year right, is the emissions toolkit current, was the model verified and how, and does the mitigation actually follow from the findings.

The last of those catches a lot of reports. An assessment concluding negligible effects and then proposing a page of mitigation is describing two different schemes. So is one concluding moderate effects and proposing nothing beyond a construction dust plan.

Where a scheme is in an air quality management area, expect a request for emissions mitigation secured by condition or obligation, often justified by a damage cost calculation. Ask early what the authority's expectation is, because the figure can be substantial and it belongs in the appraisal.

Scoping the assessment to the scheme

Proportion is set by published criteria rather than by instinct. The planning guidance produced by the Institute of Air Quality Management and Environmental Protection UK gives indicative thresholds for when an assessment is needed, based on changes in traffic flows, on the introduction of combustion plant, and on the number of car parking spaces.

Apply them and write down the result. A short scoping note explaining why a full modelling exercise is not required is often accepted, and it is far cheaper than commissioning modelling nobody asked for.

Where the answer is that modelling is required, scope it properly the first time. Adding receptors after the model has been run is straightforward. Adding a verification exercise after the fact, because the original assessment did not include one, means redoing the work.

An Air Quality Assessment is labelled as professional recommended rather than professional required, which means no statute compels a particular author. Councils nonetheless expect a suitably qualified one, and professional review before submission is strongly advised.

Questions to ask in a fee proposal

Six questions separate proposals that look similar on price.

1. Will the model be verified, against which monitoring sites, and is that included in the fee?
2. Which version of the emissions toolkit and which background year will be used?
3. Where will the traffic data come from, and does it match the transport work?
4. Is construction dust assessment included, and to which guidance?
5. Will damage cost calculations be provided if the authority requests them?
6. Who will respond to the environmental health officer's comments after submission, and is that time included?

The last one matters more than it looks. Consultation responses arrive weeks after submission, and a fee that ends at the delivery of the report leaves you negotiating a variation at the worst moment.

PlanScope's professional directory is one route to a reviewer for a draft. PlanScope provides AI-assisted draft reports for planning applications; reports should be reviewed before submission, and we do not guarantee planning approval. For specialist technical reports, qualified professional input may be required. Enter your postcode on PlanScope to see which environmental documents a scheme is likely to need.