How to Kill Mold in Ductwork

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Things You'll Need

  • Vent covers

  • Ozone machine

  • Face mask

Mold in the ductwork in your home can be a serious problem that requires your attention right away. If you or someone in your household suffers from allergies, exposure to mold can cause symptoms such as sneezing, watery eyes, coughing and difficulty breathing. Since the mold spores may not be visible in the ductwork, use a testing kit from any hardware store to detect their presence.


Step 1

Hire a professional to clean the ductwork to remove all dirt, dust and debris. These materials can encourage mold growth. A spinning head vacuum used by the HVAC professional can clean the ducts of your home. You may want to leave the house for a few hours while this is being done to avoid exposure.


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Step 2

Rent or purchase an ozone machine from a hardware store. High concentrations of ozone have been shown to kill mold spores.

Step 3

Cover all the heating/air-conditioning vents in your home. You can use small cut-out pieces of cardboard and masking tape to keep them covered while you kill the mold in the ductwork. Leave one vent open to access the ductwork for mold removal.


Step 4

Place the nozzle of the ozone machine at the vent you left open. Fire the machine for a couple of hours and then uncover the rest of the vent openings.

Step 5

Keep your heating and cooling system off for at least 24 hours after treatment.


Remember to change the air-conditioning filters regularly to prevent mold buildup within the ductwork. Many home air-conditioning systems have a filter reminder that appears on the thermostat screen when it needs to be changed.

Check the joints of your ductwork. Look for any leaks or holes and repair them. Leaky ductwork can generate mold growth and allow the spores to circulate through your cooling and heating system.


During ozone treatment, everyone should be out of the house and you should wear a face mask to reduce exposure to high levels of ozone. Also, open all of the windows in your home to provide ventilation.



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