When there’s growth near a supply vent, customers start to feel concerned and wonder if it’s inside their ductwork as well. In truth, if you remove the vent and look inside the actual duct, you likely won’t see any growth.

When cold air makes contact with the surfaces around the duct, the humidity starts to come out of the air and sit near the vent. As dust and spores from a poorly sealed boot gather on the condensation, fungal growth will happen around the vent. The solution is to seal those gaps.

In some cases, you may also need to change the direction of airflow to prevent growth from forming when condensation happens on the ceiling.

If possible, you’ll give the customer some peace of mind by reaching inside the ductwork, wiping the walls with a rag, and showing the customer that there is no mold on the rag.

Bert starts by cleaning around the vent, and then he seals all of the gaps with caulk. Sealing around the boot with spray foam is NOT a good idea because it expands and may displace the boot.