This limit can be increased to ± 750Pa if the board thickness is 40mm or greater. For larger ducts and greater operating pressures, internal stiffeners of either type shown here are required.

Internal Stiffeners
Stiffeners are constructed with strips of minimum 250mm wide PROMATECT®-L500 board and fixed at maximum 600mm centres (Type 1).

Type 1 internal stiffeners

Where a duct is subdivided by a solid PROMATECT®-L500 board, stiffeners are required with holes cut within the wall of a size and quantity to ensure equal crossflow of air between the two halves (Type 2).

Type 2 internal stiffeners

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Concrete wall penetration

Concrete Floor Slab Penetration
Same for the wall penetration, the duct should pass through the floor opening without interruption. The gap is sealed with PROMASTOP® Cement or PROMASEAL® Mortar and PROMATECT®-L500 collars are fitted around the duct on both sides on the floor, forming an L-shape, to transfer the load of the duct to the floor..

Concrete floor slab penetration

Selection of board thickness in accordance with F.R.L. & Operating Pressure requirements.
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