One, Two and Three sided Ductwork
Presently the CEN Committee (European committee for standardisation) are still writing standard EN1366-13 for this requirement. However their current understanding is that the walls move in a fire situation, which could loosen or break airtight connections to the ceiling/wall. In a fire, a 3000mm span could move up to 60mm, this movement would be simulated in a fire test situation. Due to the problem of concrete spalling, the Ducts which are not of a 4 sided construction will have to be protected on the concrete sides with at least 50% of the fire resistant Duct product used on the non-concrete sides.