HVAC and AC Mold Remediation in Broward & Palm Beach County
Down here the air conditioner runs eleven months a year, and the evaporator coil is wet the entire time it runs. That makes the air handler the most reliable place to find mold in a South Florida home — and the duct system is what carries it to every room.
Evaporator coil and fin pack — the wettest surface in a South Florida house, and where growth usually starts.
- 40–45°FEvaporator coil surface temperature — below the dew point of indoor air in South Florida for most of the calendar year.
- Under 60%The line that matters for indoor humidity — the EPA puts the ideal band at 30 to 50%. We aim for 45 to 55% in occupied South Florida homes, because holding lower than that here means running the equipment almost continuously.
- 24–48 hrsHow long a wet organic surface has before growth begins at our ambient temperatures.
Most mold calls in Broward and Palm Beach do not start with a burst pipe. They start with a homeowner who notices the house smells like a basement for the first thirty seconds after the AC kicks on, or who finds dark speckling on the ceiling ring around a supply register, or who gets an air quality result they do not understand.
All three of those point at the same place. The air handler is the wettest thing in a South Florida house, it runs continuously, and everything it grows gets pushed downstream through the ducts under positive pressure.
Why the air handler goes first
An evaporator coil works by holding a surface below the dew point of the air moving across it. That is not a side effect — that is the mechanism. The coil is supposed to be wet, because condensing moisture out of the air is half of what an air conditioner does.
What turns a wet coil into a mold problem is what lands on it. Household dust is roughly half organic: skin cells, fabric fibers, pet dander, cooking residue. A return filter that is undersized, bypassed at the edges, or three months overdue lets that dust reach the fins, where it packs into a mat and stays soaked. That mat is a substrate. The coil is the incubator.
The second factor is specific to this market: oversized equipment. A system with too much capacity for the house satisfies the thermostat quickly and shuts off before it has run long enough to pull latent heat out of the air. The result is a house that reads 74°F and 65% relative humidity — cold, clammy, and hospitable. We see it constantly in homes where a contractor replaced a failing three-ton system with a four-ton because bigger sounded better.
The seven places we find it
Ordered by how often it turns up, not by how bad it is.
- Evaporator coil and fin packA visible biofilm mat between the fins, usually on the upstream face. Restricts airflow, drops capacity, and sits directly in the supply air stream.
- Drain pan and condensate trapA clogged or dry P-trap backs water into the pan. Standing water in a dark cabinet at 75°F is the easiest growth you will ever find. This is also the failure that floods ceilings.
- Blower wheelDust cakes into the individual blades and holds humidity between cycles. A caked wheel also moves measurably less air, which makes every other problem worse.
- Fiberglass duct board plenumThe single worst offender in pre-2000 Florida housing stock. Duct board is porous. Once the mat is colonized it cannot be cleaned — only replaced.
- Flex duct interior linerCompressed, kinked, or sagging runs collect dust and condensate. Whether a run can be cleaned or has to be replaced is a judgment call we make in person, not over the phone.
- Supply register bootsWhere a cold metal boot meets a 130°F attic with failed insulation, it sweats. The drywall ring around the register goes first — that dark halo people photograph and send us.
- Return plenum and platform returnsMany South Florida homes use a framed closet or a platform under the air handler as the return. If that cavity is unsealed, the system pulls hot, humid, unconditioned air out of the garage or attic on every cycle.
Fogging is not remediation
This is worth saying plainly, because it is the most common thing done to South Florida homeowners on this problem: a company arrives, sprays a biocide into the return, runs the blower, charges a few hundred dollars, and leaves. The smell goes away for a few weeks.
Nothing was remediated. Antimicrobials work on non-porous surfaces you can physically reach and wipe. They do not restore porous material. Spraying a colonized fiberglass duct board plenum kills what is on the surface and leaves the mat intact, and the mat is the problem. When the smell returns — and it does — the homeowner concludes that mold remediation does not work.
The standard the industry actually operates under, IICRC S520, is built around source removal: physically remove the contaminated material, clean what can be cleaned to a verifiable standard, and replace what cannot. Chemicals are a supporting step at the end, never the job.
How we remediate an HVAC system
- Shut the system down and contain it The air handler stops before anything else happens. A running system during remediation is a distribution network. We build containment at the equipment and, where the ducts are involved, at the affected registers.
- Put the work area under negative pressure HEPA-filtered negative air machines exhausted outside, so the pressure differential runs into the containment rather than out of it into your living space.
- Pull and clean the blower assembly The blower wheel comes out. It is cleaned off the equipment, not sprayed in place — you cannot reach the inside faces of the blades any other way.
- Clean the coil for real Fin-safe cleaner, mechanical agitation, and a rinse that carries the debris into the pan and out the drain. A coil that has been chemically fogged and not rinsed is a coil that still has the mat on it.
- Service the pan, trap, and drain line Clear the line, verify the trap holds a seal, confirm the pan drains and the safety switch works. Skipping this guarantees a repeat visit.
- Replace what cannot be cleaned Colonized duct board plenums come out and are rebuilt in sheet metal with an appropriate liner, or in new board where that is the right call. Flex runs that are contaminated through the liner get replaced, not scrubbed.
- Clean the duct system to a source-removal standard NADCA ACR: mechanical agitation with the system under continuous negative pressure, working run by run, so the debris that gets loosened ends up in the collection unit rather than redistributed through the rest of the system. We duct that unit to the exterior, which is our practice on top of what the standard asks for.
- Correct the condition that caused it Sealing a leaking return, correcting filter bypass, adding a dedicated dehumidifier, or telling you the equipment is oversized. Remediation without this step is a subscription.
- Independent clearance testing A third-party licensed mold assessor verifies the work. Florida requires that separation, and it is the right way to do it anyway — the person who did the work should not be the person who grades it.
If your building uses fan coil units
Everything above assumes a split system — an air handler in a closet, a condenser outside, refrigerant between them. That covers almost every house and most low-rise condominiums in Broward and Palm Beach, but it does not cover the towers.
Above roughly eight stories a great many units are served by a fan coil unit instead: a compact coil and blower fed with chilled water from the building’s central plant. The growth conditions are identical — a coil held below the dew point, dust, and a condensate pan — but the access is not. Fan coils are typically mounted above a ceiling or inside a sealed soffit rather than behind an access panel, and their condensate often depends on a small pump rather than gravity drainage. Both mean the problem is found late, and a pan that overflows above a ceiling can present in the unit below rather than in yours.
It also makes more of the answer a building question than a unit question. If you are in a tower, read the Riviera Beach page — it goes into the tall-building version of this in detail.
When the duct board has to go
A large share of Broward and Palm Beach housing built before roughly 2000 uses fiberglass duct board for the supply plenum and sometimes for the entire trunk. It was cheap, it insulated and ducted in one product, and it works fine dry.
The problem is what it is. Duct board is bonded fiberglass with a foil facing on the outside and an exposed mat on the inside. That interior surface is porous and fibrous, which means it holds dust, holds moisture, and gives hyphae something to grow into rather than merely onto. There is no cleaning process that removes growth from inside a fiber mat, and there is no coating that makes a colonized one safe by sealing it in.
If we tell you the plenum has to be replaced, that is why. If a company tells you they can clean it and encapsulate it, ask them what standard they are working to.
HVAC / AC Mold Remediation: what people ask
My AC smells musty for the first minute after it turns on. Is that mold?
Usually, yes — but not always. That specific pattern, strong at startup and fading as the cycle runs, points at the coil or the pan. There is also a milder condition the trade calls dirty sock syndrome, which is a bacterial film on the coil rather than mold and produces a distinctly different smell. Either way the fix starts in the same place, and either way it is coming from the equipment, not from the room.
Can you clean the mold out of my air conditioner, or do I need a new system?
In most cases the equipment itself is salvageable. Coils, blower wheels, cabinets, and drain pans are non-porous and can be cleaned to a verifiable standard. What frequently does need replacing is the porous material attached to the system: fiberglass duct board plenums, contaminated flex duct, and saturated insulation. Full system replacement is a fair conversation when the equipment is already near end of life or when the cabinet insulation itself is colonized.
Does duct cleaning fix a mold problem?
Only if the ducts are the whole problem, which is rare. Cleaning the ducts and leaving a colonized coil upstream means you have cleaned the delivery pipes and left the source running. We assess the whole air path — return, coil, pan, blower, plenum, trunk, branches, boots — and scope the work from that, which sometimes means we tell you your ducts are fine.
How long does HVAC mold remediation take?
A contained air handler with a coil, blower, pan, and plenum is typically one full day. Add full duct system cleaning and it is one to two days. Plenum fabrication or a substantial flex duct replacement can push it to three. Independent clearance testing adds a day or two on the back end because the lab turnaround is not ours to control.
Will homeowners insurance cover this?
Be prepared for the answer to be partly. Florida policies commonly carry a mold sublimit — $10,000 is typical — and coverage generally depends on the mold stemming from a sudden, accidental, covered water event, like a supply line failure or a condensate overflow that flooded a ceiling. Gradual humidity and deferred maintenance are excluded in most policies. We document conditions thoroughly so you have what you need to file, but we will not tell you a claim is covered when we do not know that.
The air conditioning and ductwork section of our FAQ goes further, and there are 17 questions answered there in all.
Guides that go deeper on this
Written to be useful whether or not you hire us.
Where people go from here
Serving Broward County and Palm Beach County — see every city we cover.
Does the smell arrive in the first thirty seconds of a cycle?
That timing is the most useful thing you can tell us, because it separates the equipment from the ductwork before anyone opens a cabinet. Switch the system off and ring us.