Campuses: Twin Cities | Crookston | Duluth | Morris | Rochester | Other Locations

Home > Indoor Air QualityHVAC System Decontamination

HVAC System Decontamination

August, 2000




  1. Removal and disposal of visible dirt, debris, and other contaminants.
  2. Cleaning and decontamination of all supply, return and exhaust ductwork, diffusers, grilles and registers.
  3. Chemical pressure washing and decontamination of all heating and cooling coils.
  4. Cleaning and decontamination of dampers, supply air fans, exhaust air fans and other components of the HVAC systems.
  5. Removal, disinfection, and/or sealing the supply duct lining with an anti-fungicidal coating as specified in the project drawings.
  6. Verification and updating of working drawings.


  1. Product data for each product specified in this section
  2. Material safety data sheets for all products used.
  3. Project Record Documents:

  4. a.Upon completion of the project, submit one set of red-marked, duct layout drawings showing the location of all new access holes and openings installed in the duct systems to accommodate the cleaning process.
  5. Qualifications, schedules and reports:

  6. a. Qualification and experience documentation
    b. Project schedule and procedures
    c. Final report (3 copies)
  7. Product-Data:

  8. Submit manufacturer's data sheets, including Material Safety Data Sheets (MSDS) if applicable, for the following:
    a. Air-tight plastic closure plugs
    b. Vacuum cleaning machines and/or cleaning related equipment and accessories
    c. Biocide sanitizing fluid
    d. Anti-fungicidal duct work sealant
    e. Others as applicable


  1. All work in this section shall be performed by an independent specialty HVAC duct cleaning contractor. The contractor shall be certified by NADCA (National Air Duct Cleaners Association). Submit information indicating qualifications and experience.
  2. Conform to NFPA 90A
  3. Conform to the requirements of the following standards that do not conflict with regulatory requirements or requirements of the contract documents:

  4. a. SMACNA "HVAC Duct Construction Standards, Metal and Flexible."
    b. NADCA "General Specifications for the Cleaning of Commercial Heating and Ventilation Systems."
  5. Factory-Made Products - Listed by Underwriters Laboratories, Inc. (UL)
  6. Video/photographic documentation before and after the cleaning process.
  7. EPA registration for fungicide coating.
  8. A project closing report shall be submitted upon completion of the entire cleaning project. Report shall include a dated summary of the duct systems and HVAC unit inspections and approvals by the Owner's designated representative. Project closing report shall be bound, neatly presented and organized according to HVAC unit, duct system or fan. Also include photographic documentation (min. 3" x 5" color prints) of before and after conditions of each system component or section.


  1. Field measure related work to ensure proper fit and clearance.
  2. Field measure existing work to ensure proper fit and clearance.



  1. Premanufactured sheet metal patches that are crossbroke, hemmed and predrilled, with insulation to match ductwork


  1. Premanufactured access door with locking seal


  1. Product specifically rated for sealing duct work meeting NFPA requirements.
  2. Seal modifications to existing ductwork in accordance with duct sealing described in SMACNA "HVAC Duct Construction Standards, Metal and Flexible."


  1. EPA registered formula for disinfection and cleaning of HVAC equipment equal to Foster Products 40-80.
  2. Stabilized chlorine dioxide - Oxine or approved equivalent.


  1. EPA registered polyacrylate emulsion specifically formulated for long term fungicidal activity and HVAC application. Equal to Foster Products 40-20



  1. Examine elements and surface intended to support products.
  2. Verify that each product conforms to regulatory requirements and to specification requirements.
  3. Correct any unsatisfactory conditions before installing products of this section.


  1. HEPA filtered vacuum collector system capable of maintaining up to 1.0 inches of static pressure inside the isolated area of ductwork
  2. HEPA filtered wet/dry vacuums.
  3. Air compressor as required.
    a. The specific air or water pressure selected by the Contractor for air or water washing of various HVAC system components shall be appropriate to the item and component being washed. Water pressure utilized shall not exceed 1,000 psig.
    b. Contractor shall repair or replace any system component damaged as a result of using excessive air or water pressure.
  4. Rotary brush system for mechanical cleaning of ductwork.


  1. The location of each access hole or opening shall be shown and identified in a red- marked blue-lined print set of the duct system layout drawings.
  2. Seal off ends and openings of any ductwork not being immediately worked on.
  3. Isolate duct section to be worked upon, by using Protective seal barriers within the ductwork, to prevent loose dirt and debris from migrating to cleaned sections of the duct system.
  4. Protect surrounding elements from damage and disfigurement resulting from work of this section.
  5. Synthetic filter media (one inch thick 30% efficiency), or approved other, shall be temporarily fitted over each register, grille and diffuser in the duct system to intercept any migrating loose dirt and debris.
  6. Each work area shall: be protected from being soiled with polyethylene plastic sheet. A protective sheet shall cover all furniture in each room of the work area. Furniture, in the case of laboratory rooms, shall, include all laboratory benches, fume hoods, desks, and related laboratory equipment. Upon completion of the duct system cleaning in each work area, protective sheeting shall be carefully removed with collected dirt and debris disposed of in an approved manner. Vacuum clean floors and other areas in each room restoring each room to its original clean condition.
  7. Suitably support and brace any ductwork which will be entered by personnel.


  1. All work shall be conducted on an OFF HOURS basis and shall be coordinated with the designated University of Minnesota representative.
  2. Take the fans off energy scheduling and allow them to run 24 hours except when the ductwork is being cleaned.
  3. Clean the outside air intake grille and shaft.
  4. Clean the return air ducts starting at the outer ends of the return air system and concluding at the mixed air chamber and the exhaust stack.
  5. Clean the interior of the air handling unit. Remove and replace interior insulation at this time.
  6. Install products in compliance with manufacturer's instructions.
  7. Pre-vacuum diffusers, grills and registers in the ductwork. If necessary, remove, chemically wash/clean and reset.
  8. Existing ductwork and insulation shall be neatly cut as required to provide access to facilitate cleaning of the ductwork and components. As necessary, protect downstream areas from receiving particulates during the installation of access points.
  9. Install vacuum collector unit at a predetermined location and clean the section of ductwork using omindirectional air nozzles and rotary brushes as necessary. Large crawlable ducts may be hand vacuumed or brushed and air washed.
  10. Clean the supply ductwork starting from the supply fan and ending at the supply diffuser. At no point should uncleaned ductwork be upstream from clean ductwork.
  11. Location of access holes and openings shall be approved by the Owner's designated representative.
  12. Existing duct access panels shall be used wherever possible.
  13. Upon completion of the cleaning operation, the round access openings shall be plugged air-tight with plastic caps designed for this purpose.
  14. The rectangular access openings shall be closed using an overlapping galvanized sheet metal, or material to match existing ductwork, cover (cross broken) of the same gauge thickness as existing duct. Rectangular cover shall be fastened using self-tapping sheet metal screws with a silicone bead sealing gasket; or 3M No. 1202-T sealant tape used as a sealing gasket, at perimeter of cover. Seal all joints air-tight.
  15. Where ducts are provided with exterior insulation, neatly cut and remove insulation as required to accommodate required duct access holes and openings. When complete, reinsulate at ducts at access points and install new vapor barriers to match existing.
  16. Visually inspect the duct interior prior to cleaning each duct section. Use a fiber-optic borescope to accomplish the inspection task for all smaller ducts not otherwise accessible.
  17. Wash and vacuum clean each duct section:

  18. Lined Ducts: Air pressure wash and vacuum or rotary brush and vacuum. The cleaning process shall not degrade the fiberglass insulation. Damaged insulation will be replaced or repaired at the discretion of the University of Minnesota's Owners Representative.
    a. Fog the interior of the ductwork with Oxine and allow to dry.
    b. Upon completion of the cleaning of each fiberglass lined duct section, seal the surface of the fiberglass lined duct with Foster 40/20 or an approved white encapsulant equivalent.
    Unlined Ducts: Air pressure wash and vacuum or rotary brush and vacuum. Hand wipe or hand vacuum if space allows. Fog the interior of the ductwork with Oxine and allow to dry.
  19. Visually inspect each duct section using a borescope where necessary, to ensure the duct section is clean.
  20. All registers, grilles and diffusers shall be removed, vacuum cleaned, washed and then reinstalled.
  21. After duct section and reheat coils have been completely cleaned and sanitized, a final visual inspection, using a fiber-optic borescope as required, shall be accomplished with the Owner's designated representative for conditional approval. At this time, a DEHS representative will take samples for mold contamination. The cleaning will receive final approval if the total fungal counts on a surface Rodac plate sample taken from the surface of the duct do not exceed 50 colony forming units on any plate. Verbal confirmation of the clearance surface sampling results will be given seven days after the final surface sample results are taken. If the desired cleaning effectiveness is not achieved, the area will have to be re-cleaned by the Contractor. The results of the cleaning effectiveness will be included in the final report. The cleaning contractor shall provide all ladders, lighting, fiber-optic borescope, and other miscellaneous equipment required to permit the owner's representative to inspect all portions of the project.
  22. Repeat the cleaning process described above for succeeding duct sections until entire duct system is completely clean.
  23. Reinsulate the exterior of the supply duct work if the interior insulation has been removed. Design sound attenuation modification if needed.
  24. Verify that the building's air supply and return system is properly balanced.
  25. Duct Access Doors:

  26. a. Contact U of MN Facilities Management and arrange for a sheetmetal worker to install duct access doors.
    b. Install duct access doors on the side of duct where adequate clearance is available.
    c. Install duct access doors at other locations requiring access to duct interior for inspection, cleaning, adjusting, maintenance and operation.
    d. Size: 18 inches by 16 inches unless duct is too small for this size.
  27. Install duct test holes as required.


  1. Isolate HVAC unit housing from adjacent equipment and building room surfaces with polyethylene sheet.
  2. Protect all motors, bearing assemblies, and belt drive assemblies within the HVAC unit housing with taped-on polyethylene sheet to prevent intrusion of potentially damaging wash water.
  3. Carefully remove filters/filter media from holding frames and/or spools in an approved manner and store filters and protect from damage. Reinstall filter media after cleaning operation is complete, in accordance with filter manufacturer's instructions to insure a leak-free installation. Do not restart fans until all filters have been reinstalled and inspected by owner representative.
  4. Insulation on the interior of the supply fan shall be removed and replaced with exterior insulation. Alternatively, IMCOA closed cell foam insulation or its approved equal may be applied to the interior of the supply fan.
  5. Vacuum clean entire internal space of HVAC unit, including each component including component supports, frames, mounts, etc. contained therein, to remove loose dirt and debris.
  6. Pressure wash, using an EPA approved cleansing agent, each HVAC unit. This shall include all the internal surfaces of the HVAC unit housing and all the internal components of the HVAC unit including fans, cooling and heating coil banks, filter bank support frames, and contiguous control damper assemblies.
  7. Pressure washing of the heating and cooling coil banks shall be accomplished at both the upstream and downstream faces of the coils.
  8. Where deemed necessary by the Cleaning Contractor, cleansing agent solution may be separately supplied prior to pressure wash.
  9. Hand scrub where required to remove all residual dirt.
  10. Rinse thoroughly with clear water to remove any residual dirt and cleansing agent.
  11. Fan casings and impeller wheels shall be cleaned on all surfaces, inside and outside.
  12. Vacuum clean all pressure washed surfaces. Vacuum collected wash water shall be disposed of outside of the HVAC unit.
  13. A visual inspection of the HVAC unit, including all of its internal components shall be performed by the Owner's designated representative together with the Cleaning Contractor. At this time, a DEHS designated representative will take samples for mold contamination. The cleaning will receive final approval if the total fungal counts on a surface Rodac plate sample does not exceed 50 colony forming units on any plate. If the desired cleaning efficiency is not achieved, the area will have to be recleaned by the Contractor. Include this data in the final report.


  1. Apply fungicidal protective coating as per manufacturer's instructions with the HVAC system on interior fiberglass insulation that was previously cleaned and disinfected.
  2. Do not coat coils, filters, controls or fans.
  3. If the interior of a VAV box is encapsulated, the controls on the box must be protected from the encapsulant. The performance of the box must not be compromised by the duct cleaning.


  1. Inspect installed products to observe damage.
  2. Test and demonstrate as required by the governing authority.
  3. Do not allow discharge air from the fungicidal coating process to enter occupied spaces.
  4. Ceiling and wall surfaces that are damaged by this work shall be replace or repaired as required.
  5. Testing, Adjusting and Balancing.

  6. a. Secure all manual dampers at full open position.
    b. Set splitters straight with the main duct.
    c. Complete and clean the duct systems to prepare for testing, adjusting and balancing work.

  8. a. Work Area Preparation
    - Cover all terminal air outlets (diffusers, registers, grilles, etc.) with synthetic filter media at least 30% efficient. Tape filter to terminal device frame to eliminate air leakage.
    b. Purge Procedure
    - Inform Owner's designated representative that outlets have been covered with synthetic filter media at least 30% efficient.
    - Insure all filters have been properly installed.
    c. After receiving verbal confirmation about attainment of proper cleaning efficiency from a DEHS representative start HVAC units and in the event of variable speed/volume systems operate unit up and down between low and high speed to dislodge dirt and debris. Perform purge operation continuously for minimum of 1 hour.
    d. Clean-Up:
    - Remove synthetic filter media from air terminal outlets, and wash and dry outlet frame with approved cleaning solution.
    - Vacuum and clean work areas to original condition.