3.1602.15 Ventilation Existing Duct Sealing (All Building Types)

Duct Sealing
Desired Outcome: 
Improved effectiveness and efficiency of ventilation distribution system
For supporting material, see Referenced Standards.

Specifications will be field verified as appropriate to site conditions by installer (e.g., fire dampers, other obstructions)

Access to all elements of distribution system will be identified

Access to all dwelling units and elements of distribution system will be ensured by the installer

An inspection will be conducted for mold, water leaks, water damage, and breaches in the surfaces of the isolated space before sealing

Repairs will be completed before subject work

Prepare for installation

Health and safety

Health and safety concerns for occupants and workers, in relation to repairs and materials, will be addressed in accordance with OSHA OSHA U.S. Occupational Safety and Health Administration, www.osha.gov standards ( OSHA OSHA U.S. Occupational Safety and Health Administration, www.osha.gov 1926, 1910)

Area will be prepared and isolated in accordance with health and safety standards for the application and materials (e.g., extreme temperatures, lead, asbestos)

Work lighting, work platform, and adequate ventilation will be provided

Provide a safe working environment

Provide safe indoor environmental quality (IEQ) in the work environment

Provide effective repair access

Identification of leakage locations

Duct leakage sites will be identified using industry approved approaches (e.g., visual inspections, borescopes, remote cameras, infrared thermography, smoke, and/or pressure tests [ ASTM ASTM ASTM International, www.astm.org E1186-03 {2009}])

Locate air leakage pathways to repair

Identify and prioritize leakage locations to be sealed

Duct sealing opportunities will be assessed and prioritized by:

Type of hole:

1. Catastrophic holes disconnected, missing ducts, or very large holes

2. Roof curb, close to fan, register boots

3. Holes larger than 1/4"

4. Seams and joints (holes less than 1/4")


1. Easy to access

2. Demolition required

3. Access by internally applied sealants

Maximize efficiency of work effort

Temporary access

When demolition for access is specified, the installer will:

  • Make the temporary access using appropriate containment and worker protection
  • Seal ductwork in accordance with manual sealing specifications listed in row 3.1602.15h
  • Document repairs using photographs, checklist, and testing, as required
  • Repair the opening to specification

Protect occupants and workers from work-related contaminants

Seal ductwork in otherwise inaccessible locations


Ducts and registers will be cleaned before sealing

Presence and type of dampers and smoke control devices will be identified and protected from duct-sealing application

Establish preconditions for effective adhesion duct sealing materials

Ensure health and safety of occupant

Material selection

Sealants and materials will be compatible with their intended surfaces and applied in accordance with manufacturer specifications

Duct sealants will be UL UL Underwriters Laboratories 181 compliant

Sealants and materials will be continuous and meet fire barrier specifications

Ensure sealants and materials meet or exceed the performance characteristics required of the assembly (e.g., fire rating)

Duct sealing

Manual sealing of all accessible leakage areas will be completed first:

  • Reconnect disconnected ducts
  • Repair missing ducts with like materials
  • For holes greater than 1/4", backer material with mastic or appropriate sealants will be used
  • For holes smaller than 1/4", mastic or appropriate sealants will be used (Some sealed joints will allow for movement [e.g., steam pipes, deflection joints])
  • If specified, internally applied spray or aerosol sealing will only be applied after any manual sealing is complete
  • Installer will coordinate access to the ventilation ductwork in the affected dwelling units with the building management and specialized subcontractor(s)
  • Installer will provide logistical support to subcontractor(s) (e.g., remove/replace rooftop fans, mask duct terminations and openings, manually seal ducts, install flow orifices)
  • Sealants and sprays will be applied in accordance with manufacturer specifications by a qualified contractor

These final steps will be performed for all duct-sealing activities:

  • Ventilation system will be returned to operational conditions
  • Installer will document sealing was completed with photographs, checklist, and testing, as required
  • Installer will conduct final inspection and conduct close out meetings with building management

Provide proper sequencing of duct improvements

Minimize inconvenience to occupants

Prevent air leakage in ductwork

Prevent contamination of ventilation air flow

Improve effectiveness and efficiency of ventilation system


Final visual inspection of duct sealing activities and installer documentation will be completed

Continued operation of dampers and smoke control devices will be verified

Flows and pressures will be measured and balanced

Ensure the performance of the ventilation system

Ensure occupant health and safety

Combustion appliance zone testing

Pressure effects caused by fans will be assessed and corrected when found outside of combustion safety standards

Ensure safe operation of combustion appliances

Occupant/property manager education

Occupant/property manager will be educated on how the system works and its purpose

Occupant/property manager will be instructed to not alter or make holes in the ventilation duct system

Ensure the durability of the ventilation system