Approved Document B (ADB) is the guidance document that supports compliance with Part B of the Building Regulations for England. It covers fire safety in buildings - from means of escape to structural fire resistance, detection, suppression, and crucially for our industry, smoke control.
The 2022 update to Approved Document B introduced significant changes affecting how smoke ventilation systems are designed, specified, and approved on new and refurbished buildings. This article explains what changed, why it matters, and what fire engineers, specifiers, and contractors need to understand when working on UK projects.
What Is Approved Document B?
Before looking at what changed, it is worth clarifying what Approved Document B is and is not.
ADB provides guidance on one way to comply with the functional requirements of Part B of the Building Regulations. It is not a prescriptive code, and following it does not guarantee compliance: under section 7 of the Building Act 1984, compliance with ADB tends to establish compliance with the Building Regulations, and there are other routes to compliance through engineered solutions supported by BS 7346 and fire engineering analysis.
For most standard building types, ADB prescriptive compliance is the most straightforward path. For complex or non-standard buildings, engineered performance-based design is typically more appropriate.
Understanding this distinction matters because the 2022 revisions significantly expanded the guidance around when engineered approaches are appropriate - and tightened requirements in areas where prescriptive solutions had previously been applied inadequately.
What Changed in the 2022 Approved Document B Revision?
Volume 1 and Volume 2 Split
The 2022 revision restructured ADB into two separate volumes:
- Volume 1 - Dwellinghouses
- Volume 2 - Buildings other than dwellinghouses
This split reflects the very different risk profiles and design challenges of residential and non-residential buildings. Previously, a single document tried to cover both, which created ambiguity.
For smoke ventilation design, the practical impact is that practitioners working primarily on residential projects can now work from Volume 1, which provides clearer and more specific guidance on common residential scenarios including flats, maisonettes, and houses of multiple occupation.
Smoke Control in Residential Common Areas
One of the most significant areas of change affects smoke ventilation in common areas of residential buildings - particularly escape routes in apartment buildings.
The 2022 ADB provides clearer guidance on:
- Natural ventilation of common escape corridors through lobbies
- Mechanical smoke ventilation systems for common areas
- The interface between corridor ventilation and firefighting shafts
- Pressure differential systems for stair protection
For designers, this means more explicit guidance on the vent area requirements for natural ventilation systems and the performance parameters for mechanical systems. For Vent Trade customers, it reinforces the importance of using correctly specified components that meet the required performance, not simply products that appear to fit the opening size.
Changes to Sprinkler Requirements
The 2022 revision significantly extended the requirement for sprinkler systems in residential buildings. This has indirect but important implications for smoke ventilation design.
Smoke ventilation and sprinkler systems interact closely in a building’s fire strategy. Where sprinklers are fitted, the role of the smoke control system changes - sprinklers limit fire growth and spread, altering the smoke production rate and the duration for which smoke control must maintain tenable conditions.
Fire engineers need to ensure that the smoke ventilation strategy reflects the presence or absence of sprinklers. For buildings where sprinklers were not previously required but now are, a review of the existing smoke ventilation design may be appropriate.
External Fire Spread and Cladding Provisions
Following the Grenfell Tower fire in 2017, the 2022 revision introduced substantially strengthened provisions around external fire spread and cladding. While this does not directly affect smoke ventilation system design, it has had significant practical consequences for the building industry.
Many buildings subject to recladding works have required full building safety assessments, which in turn have identified smoke ventilation systems that were poorly installed, inadequately maintained, or designed to standards that no longer apply. The retrofit and remediation work flowing from cladding assessments has generated significant demand for smoke ventilation surveys and system upgrades.
High-Rise Residential Buildings
For residential buildings of at least 18 metres in height, the 2022 revision introduces more stringent requirements that sit alongside the Building Safety Act 2022 regime.
Smoke ventilation systems in high-rise residential buildings must be designed as part of an integrated fire safety strategy, and the design must be verifiable and maintainable throughout the building’s lifecycle. The concept of the “golden thread” - maintaining complete, accurate, accessible building safety information - is now embedded in regulation.
For smoke ventilation, this means:
- Design documentation must be produced and maintained
- Commissioning records must be complete and preserved
- Maintenance regimes must be documented and followed
- Changes that affect smoke ventilation performance require formal assessment
The implications for asset management and building safety case preparation are substantial for anyone managing a high-rise residential building.
What Does Approved Document B Not Cover?
It is important for practitioners to understand the boundaries of ADB.
ADB does not cover fire safety in existing buildings. The Regulatory Reform (Fire Safety) Order 2005 and, for higher-risk residential buildings, the Building Safety Act 2022, govern fire safety management in existing buildings.
ADB also does not cover all building types. Some buildings - including certain schools, healthcare facilities, and transport infrastructure - have their own guidance documents or sectoral standards that take precedence.
For buildings that fall outside ADB’s scope, or for design challenges that ADB does not adequately address, engineered approaches drawing on BS 7346 and relevant British Standards are the appropriate route.
How Does Approved Document B Relate to BS 7346?
BS 7346 is the British Standard for components for smoke and heat control systems. The standard runs to multiple parts:
- BS 7346-1:1990 - Specification for natural smoke and heat exhaust ventilators (automatic NSHEVs are now also covered by BS EN 12101-2)
- BS 7346-4 - Functional recommendations and calculation methods for SHEVS, steady-state design fires
- BS 7346-5 - Functional recommendations and calculation methods for SHEVS, time-dependent design fires (applicable to atria and many other building types; smoke curtains are NOT in this part, they are covered by the BS 8524 series)
- BS 7346-7:2013 - Code of practice for car park smoke ventilation
- BS 7346-8:2013 - Code of practice for planning, design, installation, commissioning and maintenance of smoke control systems
BS EN 12101 is a separate (parallel) European series of product standards for smoke and heat control system components, referenced by the BS 7346 codes of practice.
Where ADB prescribes a minimum vent area or airflow rate, BS 7346-4 provides the calculation methodology to verify whether a proposed design meets the performance objective. For engineers moving beyond prescriptive compliance, fluency with BS 7346-4 is essential.
Vent Trade products are designed and tested to meet the relevant sections of BS EN 12101, ensuring that components used in engineered solutions have the certified performance data required to support a fire engineering case.
What Are the Practical Implications for Specifiers and Contractors?
Review Specifications on Current Projects
If you have live projects that were designed to the pre-2022 ADB, it is worth reviewing whether the smoke ventilation design would still receive building control approval under the current version. In many cases the design will be compliant, but changes to the prescriptive requirements for residential common areas in particular may affect some specifications.
Update Standard Details and Specifications
Practices that maintain standard specifications or details for smoke ventilation should review these against the 2022 ADB requirements. Generic specifications that reference the previous ADB volumes may now be out of date.
Factor in Maintainability Requirements
The 2022 ADB and the Building Safety Act both place greater emphasis on maintainability. Smoke ventilation components must be accessible for inspection and maintenance. If a product specification does not consider maintenance access, the installation may fail inspection under the new regime.
Understand the Gateway Process for Higher-Risk Buildings
The Building Safety Act introduced a three-gateway approval process for higher-risk residential buildings. Gateway 2 (before construction begins) and Gateway 3 (before occupation) require the fire and structural safety aspects of the building to be formally approved by the Building Safety Regulator. Smoke ventilation systems are part of this assessment.
For projects on the higher-risk building path, early engagement with the smoke ventilation design is essential, as changes required at Gateway 2 can have significant programme and cost implications.
Getting the Design Right
Smoke ventilation system design is complex. The consequences of getting it wrong are serious. The 2022 ADB changes are broadly welcome - they bring greater clarity, better reflect current engineering practice, and align the regulatory framework more closely with the industry standards that practitioners already use.
But regulation alone does not make buildings safe. The quality of design, the performance of the installed components, and the reliability of commissioning and maintenance all determine whether a smoke ventilation system will do its job when it is needed.
Vent Trade has been supplying smoke ventilation equipment to the UK trade since 1988. Our product range is tested and certified to BS EN 12101, and our technical team can support specifiers with product selection, performance data, and system design guidance.
Our Managing Director chairs the SCA Maintenance Guidance working group and has been actively involved in industry engagement around the regulatory changes following Grenfell.
For technical queries on how the ADB changes affect your project, or to discuss product selection for compliance, call our technical team on 01202 725 689 or email info@vent-trade.co.uk.
Sources
Official guidance and standards referenced in this article:
