IAQM competence for air quality and construction dust
Air quality assessments are judged on method and on the person who applied it. Knowing what the guidance expects of an assessor tells you whether the report you have paid for will survive consultation.
An air quality assessment supporting a planning application should be prepared by someone with demonstrable experience of the method being used, working to the Institute of Air Quality Management guidance for the assessment type. There is no statutory licence, unlike ecology, so competence is judged on membership grade, the assessor's track record and whether the report follows the published method properly. That matters because an environmental health officer who spots the wrong method will hold up determination while it is redone, and a redone assessment usually means another monitoring season.
Developers tend to treat air quality as a box to tick. It is one of the lower cost technical reports and one of the easier ones to get wrong.
What the guidance expects of the assessor
The Institute of Air Quality Management publishes the two documents that do most of the work in the planning system: the guidance on assessing dust from demolition and construction, and the land use planning and development control guidance produced jointly with Environmental Protection UK. Neither imposes a licensing regime. Both assume a competent author who understands dispersion modelling, monitoring data and the limits of both.
In practice councils look for three things. The assessor's professional membership and grade, which is where the IAQM membership grades question comes in. Evidence that the correct guidance version has been used. And a method that matches the scale of the proposal rather than a template applied regardless.
A report that cites a superseded version of the guidance is the clearest signal that nobody senior read it before it left the office.
Screening before a full assessment
Most schemes do not need dispersion modelling. The land use planning guidance sets out indicative criteria for when an assessment is required, based on the change in vehicle movements, the introduction of new exposure close to a busy road, and whether the site sits in or near an Air Quality Management Area.
Screening should produce a written conclusion, with the traffic figures and the distance to the nearest relevant receptor stated. A one line assertion that "no assessment is required" is not screening. The council will ask for the numbers.
Where the scheme is in London, the air quality neutral requirement applies on top, with its own benchmarks and method. The rules for an air quality neutral assessment on a London scheme run separately from the national screening criteria, so a London application can need both.
Construction dust risk categories
This is the part of the report councils read most carefully, because construction dust generates complaints on almost every site.
The method separates the activity into demolition, earthworks, construction and trackout, and assesses each one. For each activity, the assessor combines the scale of the dust emission magnitude with the sensitivity of the surrounding area, which depends on the number of receptors and their proximity. The result is a risk category for each activity, and each category attracts a matching package of mitigation.
| Activity | What drives the magnitude | Typical mitigation at higher risk |
|---|---|---|
| Demolition | Building volume, height, material, method | Water suppression, soft strip inside the structure, hoarding |
| Earthworks | Area, soil type, duration, plant numbers | Damping down, stockpile management, re-vegetation |
| Construction | Building volume, materials, on-site cutting | Enclosed cutting, covered skips, sheeted deliveries |
| Trackout | Vehicle numbers, road surface, length of unpaved route | Wheel washing, road sweeping, hard surfaced haul routes |
Two points get missed. Ecological receptors are assessed separately from human ones, so a site next to a designated habitat needs its own line of reasoning. And the assessment covers dust soiling and human health effects from particulate matter as distinct issues, with different distances applied to each.
The conclusion of a well written dust assessment is almost always that effects are not significant with mitigation in place. That is the expected answer, and the value of the report is the mitigation schedule, which the council will attach by condition.
Monitoring data and its limits
Background concentrations normally come from the Defra background maps, which are modelled on a one kilometre grid from a stated base year and projected forward. Local monitoring data comes from the council's automatic analysers and diffusion tube network, published in its annual status report.
Both have limits worth knowing. Grid square backgrounds smooth out roadside variation, so they under-represent a façade three metres from a bus route. Diffusion tubes need a bias adjustment factor applied, and the factor changes year to year. Projections forward from an older base year have tended to be optimistic about real world vehicle emissions.
A modelled assessment should include a verification step comparing predicted concentrations with measured data at the same locations, with the adjustment factor stated. If the report has no verification section, ask why.
Reading an assessment critically
Work through it in this order.
- Check the guidance version cited against what is currently published.
- Check the receptor locations on the plan. Are the nearest sensitive windows and gardens actually represented, or has the assessor picked convenient points?
- Check the traffic data source and year. A count from before a nearby scheme opened is not a baseline.
- Check the verification factor and whether the model over-predicts or under-predicts.
- Check that the mitigation in the conclusions matches the risk categories in the dust assessment.
- Check whether the scheme's own emissions, from boilers or standby generators, have been assessed alongside traffic.
If you are commissioning rather than reviewing, read the fee proposal against this list. Many air quality quotes exclude verification, exclude site specific monitoring and exclude any response to consultee comments, which is where the real cost lands. Reading a consultant fee proposal properly saves that argument later.
Damage costs and mitigation secured by condition
Where residual emissions remain, some authorities seek a contribution calculated using the damage cost approach, which converts a tonnage of pollutant into a monetary value using published rates. The rates are updated periodically, so use the current published figures rather than a value carried over from an earlier scheme.
Mitigation is usually secured by condition rather than obligation: a dust management plan, a commitment to non-road mobile machinery emission standards, electric vehicle charging provision, and a low emission boiler specification. Read the condition wording before you agree it, because a condition requiring a specification you cannot source turns into a discharge problem later.
Where the assessment has to be signed off by a named professional, the professional review route is the sensible way to close that gap, and a reviewer will usually ask for the model files rather than the report alone.
An AI-assisted draft can structure the assessment, set out the method and flag the data you still need, marking anything site specific that has not been measured as still to be confirmed. It cannot run a dispersion model or stand behind the result. For specialist technical reports, qualified professional input may be required.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Who is qualified to write an air quality assessment for planning?
There is no statutory licence. Councils look for a suitably qualified and experienced assessor, normally evidenced by membership of the Institute of Air Quality Management at an appropriate grade and by a track record with the method used. The report should cite the current guidance version and show its workings, including model verification where dispersion modelling has been carried out.
When is an air quality assessment needed for a planning application?
Screening decides it. The land use planning guidance sets indicative criteria based on the change in vehicle movements, whether new exposure is introduced close to a busy road, and whether the site lies in or near an Air Quality Management Area. Record the screening conclusion in writing with the traffic figures and receptor distances stated.
How is construction dust risk assessed?
Demolition, earthworks, construction and trackout are assessed separately. For each, the dust emission magnitude is combined with the sensitivity of the surrounding area to give a risk category, and each category attracts a matching mitigation package. Human health and dust soiling are treated as distinct effects, and ecological receptors are assessed separately from people.
What is a verification factor in an air quality model?
It is the adjustment applied after comparing modelled concentrations with measured data at the same locations, correcting for the model's tendency to over-predict or under-predict at that site. An assessment that reports modelled results without a verification step gives the reader no way to judge reliability, and consultees regularly query it.
Are damage cost payments a standard requirement?
No. Some authorities seek a contribution towards air quality measures where residual emissions remain, calculated by converting predicted emissions into a monetary value using published damage cost rates. Whether it applies depends on local policy, so check the development plan and any supplementary planning document before budgeting for it.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.