Introduction
In January 2024 the Institute of Air Quality Management published Version 2.2 of its Guidance on the Assessment of Dust from Demolition and Construction, the first substantive revision of the framework since the 2014 V1.1 document. The headline change — an order-of-magnitude relaxation of the earthworks Large-magnitude threshold — has reset the risk classification of a large fraction of UK construction schemes overnight. But it would be a mistake to read V2.2 as “just a threshold update”. The 2024 guidance also strengthens the framework’s engagement with PM2.5, formalises early-stage screening, refreshes the mitigation suite, and changes how monitoring is recommended on sensitive sites.
This article walks through what actually changed and what each change means in practice, written for fellow practitioners, planning officers reviewing assessments, and developers trying to understand why a fresh assessment of the same site might now reach a different conclusion than one prepared two years ago.
The single biggest change is the earthworks Large threshold: 10,000 m² in the 2014 guidance, 110,000 m² in V2.2. The same site may now sit two magnitude bands lower than it did under the old framework.
The Earthworks Threshold Reset
The 2014 V1.1 guidance defined a Large-magnitude earthworks site as one with a total area of 10,000 m² or more. The reasoning, at the time, was that 10,000 m² was a useful proxy for the kind of operation likely to generate sufficient dust to produce off-site effects at sensitive receptors. In practice the threshold turned out to be too low. Most ordinary urban residential and mixed-use schemes — sub-hectare brownfield redevelopment, modest infill, single-block extensions to existing developments — sit comfortably above 10,000 m² once the working area of the construction site is taken into account. The framework was therefore returning “Large” magnitude for activity that, in the experience of practitioners and local-authority reviewers, was not in fact generating off-site dust at a level commensurate with that classification.
V2.2 raises the Large threshold to 110,000 m² — eleven hectares — and re-bands the Medium and Small categories accordingly. The intent is to reserve “Large” for genuinely substantial earthworks operations: major infrastructure, strategic master-planned schemes, large industrial sites, and the like. Most urban residential schemes now fall into Medium or Small. The framework still escalates the risk classification where the site sits close to highly sensitive receptors, so a small site near a school or a hospital can still attract significant mitigation requirements — but the site area itself is no longer doing the work of the assessment.
PM2.5 and the Health-Impact Lens
The 2014 framework was implicitly PM10-centric. V2.2 explicitly elevates PM2.5 in the assessment narrative, in line with the wider air-quality policy direction nationally and the 2023 revisions to the national air quality objectives. In practical terms the change is less about new calculations — the qualitative IAQM framework does not directly model concentrations at receptors — and more about how the assessment is framed and how mitigation is justified. Assessments that previously stopped at “risk of dust nuisance” are now expected to engage with the health-impact dimension of fine particulate exposure, particularly at receptors with vulnerable populations.
For most schemes this means a small expansion of the assessment narrative rather than additional fieldwork. For schemes near hospitals, schools, care homes or other receptors with concentrations of vulnerable people, the PM2.5 framing tends to drive a higher recommended mitigation tier than the magnitude alone would suggest.
Screening at Outline Planning Stage
V2.2 introduces an explicit recommendation that dust risk be screened at outline planning application stage, with the detailed assessment following at reserved-matters or full-application stage. The 2014 guidance was largely silent on outline-stage engagement, with the result that dust was often left out of outline submissions and then arrived as an unwelcome surprise during reserved matters when receptor maps had already been fixed in the wider EIA framework.
A V2.2-compliant screening note is short — typically four to six pages — and addresses three questions: is a detailed assessment likely to be triggered at the next stage, what magnitude band is the site likely to fall into, and what design or scoping responses (block layout, phasing, condition-discharge expectations) ought to be carried forward into reserved matters. The recommendation is non-binding, but local authorities have started to expect screening at outline as a matter of course, particularly in dust-sensitive contexts.
Mitigation Suite Refresh
The mitigation matrix in V2.2 is broadly recognisable from V1.1 but tightened in several places. Wheel-wash specifications have moved from “recommended” to “normally required” for any site classified as Medium or higher. Hoarding specifications have been re-articulated to address effectiveness against fine particulate rather than just visible dust. NRMM compliance — Stage V engine specifications for non-road mobile machinery, with London applying its own LEZ requirements over and above — is more prominently sign-posted as a mitigation lever, reflecting the increased weight planning authorities now place on it.
Monitoring Expectations
V2.2 references the 2018 IAQM monitoring guidance and aligns the construction-phase monitoring expectations with it. For higher-risk sites, real-time PM10 monitoring at the site boundary is now the expected baseline rather than an optional add-on. Trigger levels are explicitly discussed: the framework cites the 190 µg/m³ one-hour mean as a generic action threshold, while encouraging more stringent site-specific limits where the surrounding context warrants. The CEMP is explicitly identified as the appropriate vehicle for setting monitoring locations, trigger levels and escalation procedures.
Trackout
Trackout — dust carried off site on vehicle wheels and chassis and deposited on the public highway — remains a distinct fourth phase in the framework. V2.2 refines the assessment by tightening the link between site activity, distance from the access point to the public highway, and the receptor exposure on adjacent road links. For sites with poor access geometry — long, unpaved haul routes between activity and public road — trackout often becomes the dominant phase even where the main on-site activity is modest.
What V2.2 Means for Live Schemes
Three practical points stand out from the first eighteen months of working with V2.2 across UK schemes:
- Schemes near the old 10,000 m² threshold reclassify dramatically. A site that produced a Large-magnitude assessment under V1.1 may now sit firmly in Medium or even Small, with corresponding reductions in the required mitigation tier. Where a planning application is in the pipeline using an older assessment, a brief re-run under V2.2 can sometimes deliver a meaningful saving on the CEMP and condition-discharge stage.
- Sensitive context matters more. With the site-area driver weakened, the framework now puts more weight on receptor sensitivity. Schools, hospitals, hospices, care homes, ecological designations and AQMAs all push the assessment outcome up regardless of the headline site area.
- The outline-stage screening note becomes a useful early-flag tool. A short V2.2 screening at outline lets the design team make decisions on block siting, phasing, hoarding, NRMM specifications and condition expectations while the wider scheme is still flexible. It also reduces the risk of late surprises at reserved matters.
Where V2.2 Has Not Changed Things
It is worth noting what V2.2 has not done. The framework remains qualitative: dispersion modelling of construction dust is not introduced, nor are concentration-based receptor-level criteria. The Construction Environmental Management Plan remains the operational document through which planning conditions are discharged, and the structure of the CEMP is essentially unchanged. Significance criteria for residual effects, after mitigation, remain a matter of professional judgement — V2.2 does not introduce numerical thresholds for “significant” residual dust effect at receptors.
Air Dust Odour
Air Dust Odour prepares dust impact assessments fully compliant with the IAQM 2024 V2.2 framework, including outline-stage screening notes, full-application detailed assessments, CEMP dust sections, condition-discharge support and standalone Dust Management Plans. For a full overview of the dust offering see dust impact assessment services or our companion blog post Construction Phase Dust Impact Assessment.
Conclusion
The 2024 V2.2 update is the most consequential revision to the UK construction dust assessment framework in a decade. The headline earthworks-threshold change reclassifies the magnitude of many schemes by two bands, but the deeper change — an explicit health-impact lens, formalised outline-stage screening, tightened mitigation expectations — is at least as important. Practitioners working to the old framework will need to recalibrate; developers carrying assessments into the live planning system will want to check whether the new bands open up scope to reduce CEMP and condition-discharge costs without compromising the planning case.