Do whole-home humidifiers cause mold build up in ductwork?

Monday, November 21, 2011 by Aprilaire Team
Consumer question:

I have been told that Whole house humidifiers can cause a build up of mold in ducts. I have been trying to get an answer before I turn my humidifier back on. I turn my unit off in the summer. Please let me know if these rumors are true.


Aprilaires' response:

Thank you for contacting us regarding our whole home humidifiers. Our humidifiers are evaporative units, meaning we use moving air to absorb evaporating water. By doing this, our humidifiers add humidity to the air as a fully absorbed gas. Because we don't spray any mist or use any standing water in our units, there is no concern of mold growth when installed properly by a licensed HVAC contractor.

If you have any further questions regarding this or any of our products, please feel free to contact our customer service department at your earliest convenience.

Comments for Do whole-home humidifiers cause mold build up in ductwork?

Thursday, January 2, 2014 by Diane:
Is it common for the filter in my aprilaire humidifier to accumulate a red tint/mold? Should I be concerned?
Thursday, January 2, 2014 by brad:
Thank you for your question regarding a red tint on your Aprilaire humidifier water panel. In order for microbial growth to occur three conditions must exist: There must be an organic food source for the microbes, the temperature must be in a certain range, and water must be present for an extended period of time. These conditions can exist in some types of humidifiers, but Aprilaire evaporative humidifiers are designed to prevent microbial growth. None of the materials in Aprilaire humidifiers provide a food source. Most significantly however, the drain-through technology in Aprilaire evaporative humidifiers leaves no standing water once the humidifier turns off. All the water delivered to an Aprilaire evaporative humidifier is either evaporated or goes down the drain, leaving all surfaces dry between humidification cycles. If your water panel has a red tint this would be a sign the water panel is wet 24/7. This is usually due to attempting to achieve a humidity higher than our design humidity level of 35% at an indoor temperature of 70F and an outdoor temperature of 20F or above. We recommend replacing the water panel and reducing the humidification level to the levels we suggest on page 6 of our owner’s manual(see attached).

Thank you for giving us the opportunity to be of assistance.

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