Kitchen duct

[lyledunn]

A kitchen canopy duct is directed in to a concrete enclosed service riser which also contains other services. The duct travels up the riser to the roof at fourth floor level. Each floor has different occupancies. BC have rejected the installation as the ductwork is not fire rated. I think that they are correct to do so but the job to remove and replace is extremely difficult. Any alternatives?

[AnthonyB]

Is it within a protected shaft? If so perhaps it could be argued that will provide equivalent protection to the rest of the building

[Fishy]

BS 9999 (clause 32.5.2) recommends against this being anything other than a fire-resisting duct, and for good reason - fires in kitchen extracts are common and have lead to many large fires (e.g. the Albion Hotel fire in Brighton).  Access for cleaning might also be an issue if the riser is confined - can they not route the duct directly to outside?

If F/R ductwork is required, then don't forget that under BS EN 13501-3 the specifier should make it clear what classification of duct is required - e.g. fire inside-outside; outside to inside or both, orientation and smoke resistance etc.  For example, a classification EI60 (ve ho i↔o) S indicates a 60 minute fire and smoke resisting duct which is fire resisting in both directions and can be installed both vertically and horizontally.  Bit of a minefield...

[lyledunn]

The duct is going up a protected shaft but along with other services. The building is relatively new and is 90 min so I assume so is the shaft and its doors. However, I don't think there is any other option other than to remove existing and replace with fire resisting. As it is in shaft, I assume fire resistant from inside is satisfactory?

[Fishy]

...I assume fire resistant from inside is satisfactory?

Only if the duct doesn't transit any fire resisting walls/floors.