Airtightness is very
important in HVAC and ventilation duct systems. The ductwork itself must be
airtight but for sure the connections too . For rectangular ducts gasket tape
and sealant or mastic is used . Circular ducts are sealed with cold shrinking
tapes, aluminium tapes , pvc or cloth tapes. The circular form pieces with
rubber sealing gives alredy a good airtightness.