Fibrous glass duct insulation means durability. Their consistent resin-bonded fiber structures and tough, abuse- resistant, mat-faced or coated airstream surfaces provide long-term thermal, acoustical, and condensation control performance without deterioration and with no measurable fiber erosion. They resist damage both during installation and in service. Fibrous glass insulation products installed within the ducts may be readily cleaned in situations where dust has been allowed to enter the duct system due to absence of filtration or poor maintenance.