Fire Stopping to Vent in Masonry Cavity Wall

[Guest Tom10]

Hi all,

A little confused with regards to whether ventilation extract ducts (circa 110mm diameter) through an external masonry cavity wall need to be fire stopped internally. I don't believe there is a requirement under Approved Document B for a cavity barrier (within cavity) around the duct, but unsure if it needs to be sealed internally with an intumescent collar or would a non-fire rated sealant be acceptable to restrict air movement only. 

Would appreciate your thoughts. 

Thanks

Tom 

[Tom Sutton]

What material is the duct constructed of, and why do you think it may need fire sealing.