Smoke leakage (S): The duct shall not Have got a leakage exceeding 5 m³/h for each one m² of internal surface area space. This shall be linked to the area area on the duct from the perforated plate to the end with the duct by the inlet nozzles. In addition, https://fireresistingductworkinsu89001.livebloggs.com/43530165/facts-about-fire-resisting-ductwork-insulation-revealed