What is smoke leakage resistance (WRD)?
WRD (Dutch weerstand tegen rookdoorgang) describes how well a partition stops smoke flowing from one space into another. In a fire, smoke is often more dangerous than flames: it blocks visibility and is toxic. Good smoke control keeps escape routes as smoke-free as possible.
Classes
Under the European classification, components such as doors are tested for smoke leakage:
- Sa: tested at ambient temperature.
- S200: tested at ambient temperature and at 200 °C, the stricter class.
In the Netherlands, the building regulations (Bbl) and standard NEN 6075 set when each requirement applies. Elsewhere, national building regulations apply.
Difference from fire resistance
- Fire resistance concerns flames and heat and is expressed in minutes.
- Smoke leakage resistance concerns smoke and is expressed in classes such as Sa and S200.
A wall can resist fire for an hour and still let smoke through gaps.
Practical points
- Door gaps: smoke doors need a bottom seal, such as a drop seal.
- Penetrations for pipes and cables must be sealed all round.
- Ventilation openings count as leakage; fire or smoke dampers may be needed.
- Door closers: never wedge a smoke door open.
Related terms
- Fire-and-smoke-free escape route
- Low smoke zero halogen cable
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.