As we saw in the previous chapter we test fire rated ductwork according to different requirements, but which requirements are needed in a building.
Every building in the region has ductwork, but every ductwork can have a different purpose. Think about smoke extraction ducts, ventilation ducts, pressurization ducts, kitchen extract ducts.
This different kind of ducts requires a different set of performance, to make a building safe for people.
For example some common situations.:
Ventilation ducts
A ventilation duct needs to be tested according to a type A and type B duct. There is a risk, depending on where the fire is located in the building, that the duct needs to protect the fire from outside to inside (duct type A) or from inside to outside (duct type B).
Next to this, it is up to the designer/ consultant to prescribe if the ductwork needs to fulfill only stability and integrity or if additional insulation criteria are needed.
(note: if the ductwork is located in escape corridors or closer than 500 mm next to combustible material or person the insulation criteria is mandatory)
Smoke extraction ducts
A smoke extraction duct (like ducting in a parking garage) needs to be basically tested according to a type B duct. The main purpose is to extract smoke and hot gases from the compartment with the fire, so the fire is inside the duct.
But only a type B duct is not enough, there is a mandatory additional requirement that should be proven by a fire test. The mandatory requirement is that the duct maintains a minimal cross-sectional area of 75% during the whole test. In short, if the cross-sectional area of the duct is 1 m², during the test the duct can deform but it should not become smaller than 0.75 m² of area. This allows the duct to keep his performance of extracting smoke and hot gasses.
When the smoke extraction duct is also travelling through other parts of the building than there is an also a risk that the duct needs to protect the fire from outside to inside (duct type A).
Next to this is up to the designer/ consultant to prescribe if the ductwork needs to fulfill only stability and integrity or if additional insulation criteria are needed.
(note: if the ductwork is located in escape corridors or closer than 500 mm next to combustible material or person the insulation criteria is mandatory)
Kitchen extract ducts
A kitchen extraction duct needs to be basically tested according to a type B duct. The main purpose is to go extract smoke and hot gases from the compartment during normal use of the kitchen but also during a fire, so the fire is inside the duct.
When the smoke extraction duct is also travelling through other parts of the building than there is an also a risk that the duct needs to protect the fire from outside to inside (duct type A).
Next, to this, the designer/ consultant doesn’t have the flexibility to only describe stability and integrity. In the situation of kitchen extract ducts, the insulation criteria are mandatory.
During the normal use of the kitchen extract duct, the inside of the duct will collect oil and grease. These components are highly flammable and combustible. The insulation criteria of a duct avoid heating up the oil and grease, this means there is no ignition inside the duct by only temperature increase.
Pressurization ducts
A pressurization duct needs to be tested according to a type A. The purpose of the duct is to increase the pressure in a safety route/ escape route, because of this there is only a risk of fire outside the duct.
Next to this is up to the designer/ consultant to prescribe if the ductwork needs to fulfil only stability and integrity or if additional insulation criteria are needed.
(note: if the ductwork is located in escape corridors or closer than 500 mm next to combustible material or person the insulation criteria is mandatory)