We noted a musty smell coming from our heating ducts in the last few heating seasons. We first tried the usual things like changing filters, cleaning dust, etc., but finally called an HVAC tech to figure out why the smell wouldn't go away.

The tech told us that our HVAC furnace has a failed secondary heat exchanger. So we're getting a new furnace. However, we were also told that this can generate mold growth inside the furnace and perhaps spread the mold around the ductwork.

So I have 3 questions:

  1. What health effects should we be concerned about after having this failure for at least the past few years?
  2. Do we need to do some kind of cleaning on our ductwork as well?
  3. Do I need to replace my AC unit at the same time? I'm concerned that mold got on the coils.

We don't generally have mold problems in the main part of the house - we only have an occasional mold issue in the basement.

  1. There are some unhealthy molds, but you're surrounded by 1000s of different kinds of mold every single day and they do you no harm at all. Have yours tested if you're worried. If it turns out to be a harmful mold, then ask your doctor about the possible long-term effects of the fairly short-term exposure.
  2. IF the mold tests come back indicating that the mold is harmful, cleaning the ducts would probably be a reasonable precaution.
  3. Did you look at the AC unit to see if there was any indication of mold? Even if there is and it's determined to be harmful, it's on the outside of the coils and outside the house (where there are 1000s of harmful and non-harmful molds anyway) and will have no direct impact on the air quality inside your house.

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