Mold in HVAC & Air Ducts
Mold in an HVAC system matters more than mold anywhere else in a house because the system distributes spores to every room on every cycle. The usual site is the evaporator coil and drain pan, where condensation is constant by design, not the duct walls themselves.
Signs to look for
- A musty smell that appears only when the system runs
- Visible growth on supply registers
- Symptoms that improve when you leave the house
- A drain pan holding standing water
- Dust that rapidly returns after cleaning
What usually causes it
- A blocked condensate drain line leaving standing water
- An oversized system that short-cycles and never dehumidifies
- Dirty evaporator coils
- Duct leakage drawing humid air from crawl spaces or attics
- Filters left in far too long
Removing the growth without eliminating the water source simply resets the clock. Every report we write identifies the moisture source, because that is the finding that determines what it actually costs you to fix.
How we investigate it
Locate the moisture
Thermal imaging and moisture meters map the full extent of wet material, including behind finishes.
Establish the source
Groundwater, plumbing, condensation and ventilation failures all look similar at the surface and need completely different fixes.
Sample if it changes the plan
Air sampling with an outdoor control where growth is hidden; surface sampling where it is visible.
Document and hand off
A written report you can hand to a contractor, an insurer or a landlord — and independent clearance testing afterwards.
Related
Common questions
What causes mold in hvac & air ducts?
A blocked condensate drain line leaving standing water; An oversized system that short-cycles and never dehumidifies; Dirty evaporator coils.
How do I know if I have mold in hvac & air ducts?
A musty smell that appears only when the system runs; Visible growth on supply registers; Symptoms that improve when you leave the house.
Can I clean it myself?
Under roughly ten square feet with a known, corrected water source, most homeowners can clean it safely with gloves, an N95 and good ventilation. Above that, or where HVAC is involved, where the water was contaminated, or where someone in the household is immunocompromised, containment matters because disturbing growth spreads it through the building.
Will it come back after cleaning?
Yes, if the water source is still there. This is the single most common reason people call us twice. Cleaning removes what has grown; only correcting the moisture stops it regrowing.
Do I need a lab test for this?
Not always. If growth is visible and the cause is obvious, a laboratory result rarely changes what you should do. Testing earns its cost when the source is hidden, when documentation is needed, or when you want to verify a remediation job.
Get a straight answer about your building
We test, document and verify. We never sell remediation, so we have no reason to find a problem you do not have.