Mold in Air Ducts in Tampa Homes

What people see, and what it usually is

Black spots around ceiling registers

Often dust that has stuck to a damp surface, sometimes with mold growing on it. The cause is condensation: cold supply air meets humid indoor or attic air at a leaky boot or a register that is not sealed to the ceiling.

A musty smell when the AC starts

The drain pan, the coil, or wet insulation around the air handler, more often than the ducts themselves. A clogged condensate line in a garage air handler is one of the most common sources in Tampa.

Growth visible inside a return

Returns pull in room air that is humid in summer, especially in houses where the system is oversized and short-cycles. This is the case where the ducts genuinely need attention.

Why Tampa is hard on duct systems

The National Weather Service office for Tampa Bay dates the local rainy season from about May 25 to October 10 and describes it as a stretch of persistent dew points above 70 degrees. An AC system here is a dehumidifier as much as a cooler, and when it cannot keep up, or when its ducts leak in an attic the Florida Solar Energy Center has measured at about 40 degrees above the outdoor air, moisture collects inside and outside the ducts. Mold needs water more than anything else. Removing mold without removing the water means paying twice.

What cleaning can fix

Light growth on sheet metal ducts, the blower wheel or the cabinet can be cleaned out under negative pressure, and that is the setting where an EPA-registered sanitizer, applied after cleaning, has a legitimate role. The EPA is specific that no biocide is registered for fiberglass duct board or lined duct, and that wet or moldy fiberglass should be replaced. So a quote that proposes to "fog" a duct board system is proposing something the label does not allow.

When it becomes mold remediation

Florida licenses mold remediation through the Department of Business and Professional Regulation under Chapter 468, Part XVI. The statute defines remediation as removing, cleaning or treating mold growth over 10 square feet. Contractors licensed under Chapter 489, which includes air-conditioning and mechanical contractors, are exempt while working within their own license, but cannot advertise themselves as mold remediators without the mold license.

What that means for you: if the growth is large, or spreads beyond the HVAC system into drywall or insulation, the company you hire should be a licensed mold remediator or a licensed contractor working within its scope. Florida also licenses mold assessors, and section 468.8419 bars an assessor from remediating a structure it assessed in the previous 12 months, so the person testing is not the person selling the fix. Check either license at myfloridalicense.com.

What a sensible first visit looks like

Someone opens the air handler and looks at the coil, drain pan and blower, checks the condensate line, looks inside a return and a couple of supplies with a camera, and checks the attic for disconnected or sweating ducts. You should come away knowing where the water is coming from, whether the growth is small and cleanable or large and a remediation job, and what each option costs.