How to Clean Mold out of Duct Work

What You'll Need
HEPA air scrubber
HEPA Vacuum
Scrub brush
Disinfectant or fungicide
Mold Fogger
Ozone Generator
Plastic sheeting
Duct tape

Knowing how to clean mold is a vital skill if it has found a space to grow in your building. Moisture can build up in ventilation ducts because of condensation or leaks. This opens a foothold for mold spores. To purge the mold you will have to vacate the building and clean the air ducts intensively for over a day. Failure to thoroughly clean the mold and remove its source will invite its return. Cleaning your air ducts is not necessary or recommended by the EPA unless the ducts are contaminated with mold.

Step 1 – Open Air Duct

Unscrew the vent grilles and inspect the interior of the duct using the flashlight. Check for visible growth, black or green spots, or a pungent smell. Clean the vent grilles with bleach.

Step 2 – Verify Mold Contamination

If you suspect mold growth, take action to abate it immediately. Environmental hygienists are trained to capture air samples from inside and outside the building. A laboratory analyzes the samples to determine concentrations of mold spores. This test is the only way to confirm a mold infestation.

Step 3 – Isolate Contamination

As soon as you believe there is mold contamination in your building, shut down the central air handler. If mold spores collect in the handler, the fan will distribute them throughout the house. Determine the site of mold growth and isolate it from the rest of the building using plastic sheeting and duct tape to seal off openings. Perform the abatement under negative air pressure using HEPA filtration. Wear a respirator and personal protective equipment when performing mold abatement work. Double-bag contaminated debris for removal.

Step 4 – Discard Moldy Insulation

If mold has spread outside the ductwork, cut off and discard contaminated insulation and drywall.

Step 5 – Scrub Mold

Determine whether the ductwork is made of stainless steel or fiberglass. Scrub the inside of the ventilation ducts with a brush or rag and a disinfectant. Do not scratch fiberglass ductwork. Beware of materials containing asbestos.

Step 6 – Fumigate Mold

Several options are available for spraying gas into ductwork to remove mold infestations. This is critical to removing the infestation. A mold fogger aerosolizes a mixture of disinfectant fungicides. Many types of mold cleaning solutions are available. However, only use nontoxic and noncorrosive solutions in ventilation ducts. This limits your options. You can also use an ozone generator. The generator asphyxiates mold by removing oxygen from the atmosphere. Either option will require all occupants to vacate the building for several days. When selecting an ozone generator, choose a model large enough to generate a high concentration of ozone. Undersized units will not completely eliminate the mold.

Step 7 – Post Abatement Follow-Up

After the mold abatement is complete, a post-test from the laboratory will confirm reduced concentrations of mold spores and better indoor air quality. Now you can replace the ductwork, insulation, and drywall that had to be removed.