What DW/172 is
DW/172 is the HVCA-recommended specification for the construction of kitchen ventilation ductwork. It sets out how kitchen extract ductwork should be built, so it can safely handle grease-laden air without becoming a fire risk or a cleaning nightmare.
Construction methods
Ductwork manufactured to DW/172 can be built from mild steel, fully welded with angle iron flanges, or from galvanised steel with mezz flanges. The right choice depends on the kitchen's cooking load, the ductwork run and the client's budget — but either way, every joint needs to be sealed properly, since grease-laden air will find any gap over time.
Access for cleaning
A compliant DW/172 system includes suitable access doors positioned along the ductwork run, so it can be inspected and cleaned regularly without having to dismantle sections of the system. Given that grease build-up inside ductwork is one of the most common causes of commercial kitchen fires, this isn't a nice-to-have — it's central to the standard.
Fire-rated ducting
Where a ductwork run needs to pass through fire compartment walls, or where local regulations demand it, fire-rated ducting can be specified as part of the same system — maintaining the building's fire strategy without compromising extraction performance.
Why it's paired with BS6173
DW/172 ductwork and BS6173 gas interlocking are often specified together, because one governs how safely air moves out of the kitchen, and the other governs when gas appliances are allowed to run. Cool Stream Ventilation manufactures ductwork to DW/172 as standard on every kitchen extraction project, and tests canopies for conformity to BS6173 before hand-over.
