DW/172 is BESA's specification for commercial kitchen ventilation systems. It provides a recognised technical framework for designing, installing, commissioning and maintaining systems that capture and remove heat, steam, grease, smoke, odour and combustion products while replacing the extracted air. It is an industry specification—not an Act of Parliament.
Which version is current?
BESA lists the current publication as the second edition, published in 2018, incorporating a May 2024 addendum. The addendum includes updated guidance connected with fire-resisting and smoke-control ductwork.
Older drawings and specifications may still refer to the 2005 edition or the 2018 document with its earlier 2020 addendum. A project team should state the exact edition and addendum it is using.
What DW/172 covers
BESA's publication information identifies DW/172 as the industry specification for kitchen ventilation. Its scope includes the connected elements of a working system rather than only the canopy or fan.
Key areas include:
- assessment of cooking-appliance loads;
- extract air quantities;
- canopy and ventilated-ceiling design;
- capture and containment of cooking emissions;
- grease separation;
- replacement and supply air;
- ductwork and discharge;
- fans, controls and commissioning;
- solid-fuel appliances;
- demand-controlled kitchen ventilation;
- recirculation systems;
- lighting and other canopy considerations;
- access, cleaning and maintenance.
The full specification is a paid technical document. A blog can explain its purpose, but it should not reproduce its coefficient schedules, design tables or protected diagrams.
Is DW/172 law?
No. DW/172 is not legislation and there is no blanket offence called “breaking DW/172”.
That does not make it optional in the casual sense. UK law creates duties around suitable workplace ventilation, gas safety, fire safety and safe building work. Designers, clients, insurers, building-control bodies and environmental-health teams can use recognised specifications to judge whether a system has been competently conceived and delivered.
Regulation 6 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires sufficient fresh or purified air in enclosed workplaces. The HSE's CAIS10 guidance explains how kitchen ventilation should remove fumes at source and introduce adequate replacement air. DW/172 provides the kitchen-specific technical framework used by the industry to develop that into a system.
Contracts, planning conditions or specifications can also expressly require work to follow DW/172. In that situation its status within the project is created by those documents as well as its technical standing.
Why appliance information comes first
A canopy cannot be designed properly from wall length alone. The proposed cookline affects the heat, steam, grease, smoke and odour released into the room.
The design brief should identify:
- exact appliance type and fuel;
- manufacturer and model where possible;
- dimensions and configuration;
- cooking process and intensity;
- whether doors or lids release a plume when opened;
- future equipment changes the operator realistically expects.
This is why moving a fryer, changing from electric to gas or adding a charcoal appliance is not simply an operational decision. It can alter the ventilation, gas, fire and odour-control requirements.
Capture and containment—not just airflow
More fan power does not automatically fix poor capture. The canopy has to receive and contain the rising plume before room air currents carry it into the kitchen.
Performance can be affected by:
- insufficient overhang;
- appliances projecting beyond the capture zone;
- cross-draughts from doors or supply-air grilles;
- badly placed light fittings or obstructions;
- excessive or poorly distributed replacement air;
- side exposure around island canopies;
- filters and ductwork imposing more resistance than allowed for;
- changes made after commissioning.
A competent designer considers the appliance plume, hood geometry, room air movement and complete system resistance together.
Replacement air is part of the same system
Air extracted from a kitchen must be replaced. If it is not, the room can become excessively negative relative to adjacent areas.
Possible consequences include:
- doors becoming difficult to open;
- strong draughts;
- poor canopy capture;
- air being pulled from toilets, waste areas or dining spaces;
- interaction with combustion appliances and flues;
- staff discomfort;
- actual fan duty differing from the design assumption.
DW/172 therefore should not be interpreted as an “extract-only” document.
Grease separation, ductwork and cleaning access
Grease should be separated at the canopy before it accumulates through the system, but no practical system removes every particle. Ductwork and fans still need to be inspectable and cleanable.
DW/172 should be coordinated with:
- DW/144 for sheet-metal ductwork manufacture and installation;
- TR19® Grease for grease inspection, cleaning and fire-risk management;
- the building's fire strategy and applicable Building Regulations;
- planning and environmental requirements for discharge, odour and noise.
These documents do different jobs. Stating that a duct is “DW/144” does not by itself demonstrate that the complete kitchen extract system meets the kitchen-specific requirements.
Commissioning proves what was delivered
A design calculation is not the end of the project. Commissioning should establish that installed air quantities, balance, controls and interlocks operate as intended and that the client receives useful records.
Ask for:
- design intent and calculations;
- as-installed drawings;
- fan and equipment data;
- measured extract and supply results;
- control and interlock demonstration;
- operating and maintenance information;
- filter and cleaning requirements;
- access arrangements;
- identified limitations or outstanding items.
Common DW/172 misunderstandings
“It is law”
It is a technical specification. Legal duties and project documents give the wider context.
“The canopy supplier deals with all of it”
Responsibilities must be defined. Canopy manufacture, system design, ductwork, fans, replacement air, electrical controls, gas interlocks, fire treatment and commissioning may involve different specialists.
“An air-change rate is enough”
General room air changes do not replace appliance- and canopy-based capture design.
“Electric equipment does not need ventilation”
Electric equipment can still release substantial heat, steam, grease, smoke and odour. Gas-specific requirements change, but the ventilation question remains.
“Once commissioned, the system can be forgotten”
Filters, ductwork, fans, controls and odour-treatment equipment require inspection and maintenance. Menu or appliance changes should trigger a review.
Plan the system before work starts
The KIG 317 Commercial Kitchen Installation Guide helps project teams connect DW/172 considerations with the wider kitchen layout, gas, utilities, planning and installation process.
Sources and further reading
- BESA: DW/172 Specification for Kitchen Ventilation Systems
- NBS publication index: current DW/172 edition and May 2024 addendum
- HSE: Ventilation of kitchens in catering establishments
- Workplace Regulations 1992, regulation 6
This article explains the role of DW/172 but does not reproduce or replace it. Use the current paid specification and a competent designer for a real project. Last reviewed: 13 August 2026.