Air Quality and Ventilation Strategy, Condition 9, Hammersmith

Air Quality Assessment and Ventilation Strategy for Condition 9 on a Change of Use at Dalling Road, Hammersmith
Location: 186 Dalling Road, London, W6 0EU | Services: Air Quality Assessment; Ventilation Strategy

An AQMA Designation Is a Starting Point, Not a Verdict

The site lies within the Hammersmith and Fulham Air Quality Management Area, declared on 3 November 2000 across the whole borough for the annual mean nitrogen dioxide and 24-hour mean PM10 objectives. A borough-wide AQMA tells you very little about a specific address. It is a policy boundary drawn around an authority that could not demonstrate compliance everywhere; it is not a measurement at the site.

We were appointed by an architect's practice to prepare a Ventilation Strategy Report, together with the screening-level air quality assessment on which it rests, for the change of use of the basement and ground floor of 186 Dalling Road, London W6 0EU, from Class E(c)(ii) to Class C3, and the conversion of the building into a four-storey single family dwellinghouse. Full planning permission was granted by the London Borough of Hammersmith & Fulham on 10 November 2025 under reference 2025/02481/FUL. Condition 9 of that permission requires the Ventilation Strategy Report to be submitted to and approved in writing by the Local Planning Authority before above-ground works commence.

The Monitoring Data

The assessment went to the monitoring data rather than to the designation. The nearest indicative monitoring, at Brackenbury Primary School 159 metres north on Dalling Road, recorded an annual mean nitrogen dioxide concentration of 28.2 µg/m³ in 2024 against the 40 µg/m³ objective. London Atmospheric Emissions Inventory concentrations interpolated to the 2027 opening year indicate 19.6 µg/m³ nitrogen dioxide at the site. Both figures sit below the objective by a margin of at least 29%.

We reviewed the borough's latest Annual Status Report and its Air Quality Action Plan alongside the Defra background maps, so that the site figures could be read against the borough trend rather than as isolated numbers.

What That Means for the Ventilation Specification

Condition 9 applies a stricter test than the national objectives. The council's Air Quality Action Plan 2025-2030 adopts the World Health Organization (2021) guideline values as borough targets for 2030: 10 µg/m³ nitrogen dioxide, 15 µg/m³ PM10 and 5 µg/m³ PM2.5 as annual means. Measure 1 of the plan requires mitigation where those targets are exceeded or approached within 5%, and Condition 9 reproduces that test almost word for word. With 19.6 µg/m³ nitrogen dioxide, 15.7 µg/m³ PM10 and 9.6 µg/m³ PM2.5 indicated at the site for 2027, all three targets are exceeded. Condition 9 is therefore engaged at every residential floor, and the ventilation strategy was designed to the requirements of the condition.

The dwelling is to be served by a single whole-dwelling balanced mechanical ventilation system with heat recovery (MVHR), located in the basement utility room. Approved Document F gives a whole-dwelling supply rate of 37.6 l/s, and the design supply rate is set at 38.6 l/s so that the dwelling is held at slight positive pressure. Supply air is drawn through a single intake at rear roof level and discharged through a single exhaust 2.60 m away, against the 2.00 m minimum the condition sets. There are no other external ventilation penetrations, and the existing gas boiler flue on the rear elevation is to be removed. The intake and exhaust positions are marked up on the drawings in the report.

Supply air is to be filtered through an ISO 16890 ePM1 80% particulate stage, with ePM2.5 and ePM10 efficiencies of at least 90% and 95%, and through an activated-carbon stage tested to BS EN ISO 10121-1 achieving a nitrogen dioxide removal efficiency of at least 90%. That is the filtration Condition 9 requires. Restricted openers limiting normal opening to 200 mm are to be fitted to all habitable-room windows on all floors.

Summer overheating is addressed through 100% automatic summer bypass, and energy use through sensible heat recovery of at least 90% and a specific fan power of no more than 1.0 W/(l/s).

The Screening Assessment

The development's own impacts were screened against the EPUK/IAQM criteria (January 2017). The scheme introduces one dwelling on a site with no car parking provision, and falls below every indicative screening criterion: for traffic generation, for car park size and for combustion plant. No dispersion modelling was required, and none was undertaken. Construction dust was addressed by reference to the IAQM guidance and the standard mitigation appropriate to a conversion of this scale.

Outcome

The report sets out the measures for each part of Condition 9, with the post-installation compliance report required by Condition 10 to follow. No decision on the condition had been published at the time of writing. In Hammersmith & Fulham a ventilation condition of this kind should be expected on new homes: Measure 1 of the Air Quality Action Plan requires mitigation wherever the WHO-aligned 2030 targets are exceeded or approached within 5%, and at this site they were exceeded although the national objectives were met by a margin of at least 29%.