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1. Before you schedule the cleaning:

  1. Ask the cleaning service to inspect your building(s) and to recommend a separate company to provide a baseline survey of air ducts. If the system has any asbestos-containing materials, specially trained and equipped contractors will be required.
  2. Get a written estimate and agreement outlining what services the cleaner will provide and the total cost.
  3. Check that the service is trained, experienced, and has the necessary state licenses. Ask for references from similar and completed projects, and if the contractor is a member of National Air Duct Cleaners Association (NADCA).

2. During the air duct cleaning, the service should:

  1. Open access ports or doors to allow the entire system to be cleaned and inspected.
  2. Use state-of-the-art vacuum equipment, including HEPA filters, sufficiently powerful to remove contaminants.
  3. Follow National Air Duct Cleaners Association (NADCA) and North American Insulation Manufacturer Association (NAIMA) standards.

3. After the cleaning, the service should:

  1. Document the cleanliness of your heating and cooling system using remote photography.

4. You should inspect your heating and cooling system:

  1. Verify cleanliness. Are surfaces free of debris, dust and mold? Is the supply air plenum free of moisture stains and contaminants?
  2. Do filters fit properly?
  3. When the system is running, is there air leakage through access doors? Leakage should be slight or non-existent. Are newly installed access doors in sheet metal ducts firmly attached?
  4. Does the entire system function properly?

To grow, fungi need a source of nutrients and moisture for more than 24 hours. Dust in the system provides enough food for fungal growth.

  1. Check for musty odors. If you remove the moisture, the fungal spores will be dormant, but they can grow if moisture is present.
  2. Look for discolorations-in general: green, black, white, and/or pink.
  3. Check for slimy, turbid or sludgy standing water in the air handling unit.

Use a careful preventive maintenance program to reduce contamination. To prevent dirt from entering the system:

  1. Use the highest efficiency air filters recommended by the manufacturer of your heating and cooling system.
  2. Change filters regularly; post a schedule for maintenance crews to observe. If they are clogged on inspection, filters may need more frequent changing. The filter holders must fit correctly so air cannot bypass filters through gaps.
  3. Heating and cooling system maintenance must include cleaning cooling coils and drain pans.
  4. During building construction or renovation that produces dust, seal off supply and return registers. Do not operate the heating and cooling system until all dust is cleaned up.
  5. Operate humidifying systems strictly as recommended by their manufacturer.

Don’t let moisture get into the ducts to control mold. It’s not always easy. Moisture gets in if there are leaks or if the HVAC system is improperly installed or serviced. Condensation on or near air conditioning cooling coils is another major factor in moisture in the system.

To prevent moisture (and mold contamination):

  1. Repair any leaks or water damage as soon as you find them.
  2. Make sure condensate pan drains properly.
  3. Heating and cooling system maintenance must include cleaning cooling coils and drain pans.
  4. Check any insulation near cooling coils for wet spots.
  5. Make sure ducts are properly sealed and insulated in all non-air-conditioned spaces, such as crawl spaces.

U.S. Environmental Protection Agency

Indoor Air Quality Information Clearinghouse (IAQINFO)

P.O. Box 37133

Washington, DC 20013-7133

(800) 438-4318 or (202) 484-1307

FAX (301) 588-3408

Web Site:www.epa.gov/iaq

Ask for:

  1. The Inside Story: A Guide to Indoor Air Quality IAQ-0009
  2. Building Air Quality: A Guide for Building Owners and Facility Managers
  3. Fact Sheet: Ventilation and Air Quality in Offices IAQ-0003
  4. Check any insulation near cooling coils for wet spots.
  5. Fact Sheet: Sick Building Syndrome IAQ:0004

Consumer Research Council IAQ Checklist

P.O. Box 12099

Washington, DC 20005-0999

National Air Duct Cleaners Association (NADCA)

1518 K Street, NW Suite 503

Washington DC 20005

(202) 737-2926

Web Site: www.nadca.com 

Ask for:

  1. Introduction to HVAC Cleaning Services
  2. NADCA Standard 1992-01, Mechanical Cleaning of Non-Porous Air Conveyance System Components

North American Insulation Manufacturers Association (NAIMA)

44 Canal Center Plaza, Suite 310

Alexandria, VA 22314

Ask for:

  1. Cleaning Fibrous Glass Insulated Air Duct Systems: Recommended Practices
  2. Fibrous Glass Duct Construction Standards

National Antimicrobial Information Network (NAIN)

(800) 447-6349

E-mail: nain@ace.orst.edu 

Sheet Metal and Air Conditioning Contractor’s National Association (SMACNA)

4201 Lafayette Center Drive

Chantilly, VA 22021

(703) 803-2980

Ask for:

  1. HVAC Duct Construction Standards – Metal and Flexible

National Air Filtration Association

1518 K Street, NW, Suite 503

Washington, DC 20005

(202) 628-5328 FAX (202) 638-4833

Ask for:

  1. NAFA Guide to Air Filtration ISBN 1-884152-00-7

U.S. Department of Labor

Occupational Safety & Health Administration (OSHA)

Room N3651

200 Constitution, NW

Washington DC 20210

(202) 219-6666

Ask for:

  1. All About OSHA OSHA 2056
  2. Control of Hazardous Energy OSHA 3120
  3. Respiratory Protection OSHA 3079
  4. Chemical Hazard Communication OSHA 3084
  5. Personal Protective Equipment OSHA 3077

American Society of Heating Refrigeration and Air Conditioning Engineers(ASHRAE)

1791 Tullie Circle, NE

Atlanta, GA 30329

(404) 636-8400

Ask for:

  1. Ventilation for Acceptable Indoor Air Quality

The National Air Duct Cleaners Association recommends asking these questions:

  • How long have you been cleaning HVAC systems?
  • Is your firm properly licensed to work in this state?
  • Are you fully insured?
  • What experience have you had cleaning systems similar to those in my systems?
  • What references can you provide of completed similar projects?
  • Who will be the on-site supervisor for this project? How many similar projects has he/she been responsible for?
  • Will you use source removal techniques in accordance with NADCA Standard
  • 1992-01?
  • Do you completely understand the NADCA Standard and will you comply?
  • Do you have a comprehensive in-house safety program with employee training?
  • Are you aware of site-preparation issues?
  • Is your equipment in good repair, working properly? When did you buy it? How long have you used it?
  • Can you provide a scope of work?
  • Do you have a current membership certificate from NADCA? Are you a member in good standing?
  • Do you have a NADCA certified Air System Cleaning Specialist on staff?