DW/144 vs DW/172 vs TR19 Grease Explained

DW/144, DW/172 and TR19® Grease are connected but not interchangeable. DW/144 covers sheet-metal ductwork manufacture and installation, DW/172 covers the complete commercial kitchen ventilation system, and TR19 Grease covers inspection, cleaning and fire-risk management of grease accumulation in kitchen extract systems.

The simple comparison

Document Main question it answers Project stage
DW/144 How should sheet-metal ductwork be constructed and installed for its pressure/velocity class? Design, manufacture and installation
DW/172 How should a commercial kitchen ventilation system be designed, installed and commissioned? Brief, design, installation and commissioning
TR19® Grease How should grease accumulation be inspected, cleaned, evidenced and managed as a fire risk? Operation, maintenance and design-for-cleanability

All three are BESA publications. None should be described as a substitute for legislation, the building fire strategy or competent design.

What DW/144 does

BESA describes DW/144 as the recognised industry standard for sheet-metal ductwork used in building-services engineering. It addresses low-, medium- and high-pressure/velocity air systems and provides a consistent basis for specifying, fabricating, installing and testing ductwork.

The current NBS record identifies the third edition from 2016 with an April 2024 addendum.

DW/144 addresses duct construction quality. Kitchen extract adds special grease, access and fire considerations that require the kitchen-specific documents and fire design.

What DW/172 adds for kitchens

DW/172 deals with the system serving the cooking process. It connects:

  • appliance loads;
  • canopy or ventilated-ceiling design;
  • capture and containment;
  • extract quantity;
  • grease separation;
  • replacement air;
  • ductwork and discharge;
  • fans and controls;
  • solid-fuel and recirculating arrangements;
  • commissioning and maintenance access.

The current publication is the second edition from 2018 incorporating a May 2024 addendum.

Specifying “ductwork to DW/144” does not answer whether the canopy captures the plume, the air quantity is correct, the grease duct is cleanable or the discharge creates an odour problem.

What TR19 Grease does

BESA's TR19® Grease is the specification for fire-risk management of grease accumulation in kitchen extraction systems.

It covers best practice for inspection, cleaning and evidence across the system. The design has to make those tasks possible through appropriate access and construction.

TR19 Grease should not be reduced to the phrase “annual duct clean”. Cleaning frequency depends on use, grease loading, inspection findings, risk and the current specification. A high-volume frying operation can need a different regime from a low-intensity kitchen.

Fire strategy sits above the shorthand

Kitchen extract ductwork can pass through walls, floors, risers, escape routes and other compartments. The fire strategy must address how the route affects compartmentation and fire/smoke spread.

Depending on the building and design, matters can include:

  • fire-resisting ductwork or enclosure;
  • penetration sealing;
  • support under fire conditions;
  • access panels without undermining fire performance;
  • interfaces with dampers and why ordinary fire dampers may be unsuitable in grease extract;
  • fan operation or shutdown strategy;
  • fire suppression;
  • clear separation from combustible materials;
  • discharge and roof construction.

Do not select a detail from a generic HVAC duct and assume it applies to grease extract. Use the building's competent fire designer and the current approved design.

Cleanability has to be designed in

A grease duct should be inspectable and cleanable along its full route. Common failures include:

  • long inaccessible horizontal runs;
  • access panels blocked by ceilings or services;
  • a fan that cannot be opened or removed;
  • no safe roof access;
  • panels located above fixed equipment;
  • decorative enclosures installed over access points;
  • sharp changes and dead areas that trap grease;
  • no record of the concealed route;
  • access doors that compromise a fire-rated system.

Agree cleaning access with the ventilation and fire design before construction.

What a specification should state

Avoid the vague note “duct to DW/144/DW/172/TR19”. A useful project specification identifies:

  • exact document editions/addenda;
  • system classification and construction requirements;
  • kitchen-specific grease-tightness and jointing provisions;
  • route and fire-resistance strategy;
  • access-panel locations and performance;
  • support system;
  • cleaning and inspection access;
  • testing and commissioning;
  • as-built records;
  • initial condition and handover requirements;
  • maintenance responsibilities.

The client should be able to trace which contractor owns each item.

What operators should keep after handover

  • as-installed duct route;
  • access-panel schedule;
  • fire-system evidence and product details;
  • ventilation commissioning results;
  • cleaning contractor reports;
  • before/after photographs where provided;
  • grease measurements or condition assessments used to set frequency;
  • identified inaccessible or damaged sections;
  • fan and filter maintenance records;
  • changes to the cookline or operating hours.

This evidence helps the operator, landlord, insurer, fire-risk assessor and future contractor understand the actual system.

Make the three documents work together

The KIG 317 Commercial Kitchen Installation Guide helps teams connect ductwork construction, kitchen ventilation, fire considerations and ongoing access instead of treating them as isolated specifications.

Sources and further reading

This is a document map, not a ductwork or fire design. Use current publications and the building's competent ventilation and fire professionals for the actual system. Last reviewed: 13 August 2026.