Smoke leakage (S): Failure of the criterion shall have happened In the event the movement charge in duct A in the course of the check exceeds 10 m³ / (m² h), related to twenty °C and 1013 mbar, relevant to The interior surface area of your duct Within the furnace. https://shaneypfth.kylieblog.com/37395967/fire-rated-insulation-for-ductworth-an-overview