If duct cleaning is determined to be the best option:

1. Hire a duct cleaning contractor who is a member in good standing of the NADCA. Duct cleaning companies must meet certain requirements to become NADCA members. All NADCA members must have certified Air System Cleaning Specialists (ASCS) on staff who have taken and passed the NADCA Certification Examination.
2. PROTECT building occupants during and after duct cleaning:
   1. Place a filter over supply and return grills to capture dust when HVAC system is placed back into service after cleaning.
   2. Perform duct cleaning during hours when the building is unoccupied, such as nights and weekends.
   3. Use containment barriers and proper ventilation equipment, such as "negative-air" machines equipped with high-efficiency filters.
   4. Avoid the use of biocides and sealants. Even EPA-registered biocides may pose health risks, including eye, nose, and skin irritation.
   5. No biocides are currently EPA-registered for use on fiberglass duct board or fiberglass-lined ducts. Both the EPA and NADCA recommend replacing wet or moldy fiberglass duct material.Consult with occupants with medical conditions (e.g. immunosuppressed individuals).

BEFORE hiring a duct cleaning contractor, make sure you can answer "Yes" to all of these questions:

• Are there known or observed contaminants in the ductwork?
• Have you confirmed the type and quantity of contaminants based on testing or observation?
• Are the contaminants (or their by-products) capable of entering occupied spaces?
• Have you identified and controlled the source of contaminant?
• Will the duct cleaning effectively remove, inactivate, or neutralize the contaminant?
• Have you considered other options, such as removal of affected ductwork? Is duct cleaning the only (or most effective) solution?

In all cases, duct cleaning should be undertaken only after the source of the contaminant has been identified and controlled. Otherwise, the problem will not go away. For instance, the water source causing mold growth must be identified and controlled or duct cleaning will be only a temporary fix.