Smoke leakage (S): The duct shall not Use a leakage exceeding five m³/h for every one m² of inner surface space. This shall be linked to the area space on the duct from the perforated plate to the top in the duct by the inlet nozzles. Fire resistant board for https://fire-resisting-ductwork-i45567.blogmazing.com/35862126/rumored-buzz-on-grease-tight-extract-ductwork