A different solution from the one discussed above are the multi-plane dampers. They allow the use of knees, arches and offsets right behind the hatch. However, pay attention, that the multi-blade fire dampers currently available on the Polish market are made of steel sheet. Due to the above, fire resistance in terms of insulation can only be achieved if a sufficiently long section of the ventilation duct is insulated on both sides of the damper with fireproof insulation.. This means additional time and material expenditure as well as the inconvenience of this solution in relation to the dampers, which do not require the above additional work. In addition, in this type of solutions, the fire resistance of the hatch depends on the quality of assembly works carried out under building conditions.
Intumescent gaskets are usually not used in multi-plane dampers. In order to meet the requirements of class S, in multi-plane flaps, additional seals are used on the axes of the blades and on the edges of the blades.
In most cases, in multi-blade dampers, the control mechanism is located in the light of the damper, which means, that the mechanism, after the hatch has been built in, is in the light of the building partition.