Mold in air ducts is growth on the cold, damp metal and lining inside your HVAC system, and the musty smell tends to show up before anything you can see. Getting it out takes two steps: clean the surfaces, then treat them with an EPA-registered product. Air duct cleaning and treatment is $50 a vent on the same visit as whole-home disinfection, or $399 minimum booked on its own. Whole-home disinfection for mold is $0.30 per heated square foot with a $200 minimum. Both come with a 12-month written guarantee.
See your price
- Whole-home disinfection: $0.30 per heated sq ft ($200 minimum)
- Clean the vents on the same visit: $50 each (no extra minimum)
- Both include Bactronizing with BactroKill Plus + 12-month written guarantee
Not sure what you need?
Start with the vents
A smell that rides the air is growing in the duct work. We scrub each vent and return with a rotary brush, clean the registers, the coil and the outside of the air handler, then treat them. $50 a vent, from $399 on its own. Spores travel on the air, so most people add the whole-home disinfection on the same visit, and then the vents carry no minimum. 12-month written guarantee.
Start with the whole home
A smell that sits in the rooms, or came with the last people, is on the surfaces, not only in the air. Whole-home disinfection sprays every surface in the house, closets included, plus the duct work and the drain pan: $0.30 per heated square foot, $200 minimum, about 30 to 75 minutes, and you can stay home. Dust or growth in the vents needs cleaning first, so add the air duct cleaning at $50 each on the same visit if the vents are dirty. 12-month written guarantee.
We look first
Mold you can see gets wiped off, not sprayed over. Every one is different, so we look before we price it, and Greg puts the price in writing before any work starts.
Fix the water first
Mold is a water problem first. Wet material grows again, so the leak, the flood or the drain line gets fixed before anything is sprayed. Once it is dry we treat it, and if something is still wet we say so before we start.
Two ways to be sure
If you can smell it or see it, the CDC says you do not need to know the type, so most people skip the test and treat. To be sure anyway: while we are at the house we can swab a surface and read it on a hand-held meter, or send samples to a lab, $350 for two and $450 for four.
Request a window Or start with the treatment Call 843-282-7777
Open now. Closes at 4 pm.
Call 843-282-7777Request a windowGreg confirms it in writing.Do not know the square footage? Request a visit without a number. We work it out when we come out.
Veteran owned. Licensed and insured. EPA-registered product. 12-month written guarantee.
How do you know if you have mold in your air ducts?
The clearest sign is a musty smell when the HVAC runs that fades when it shuts off. Here are seven signs, roughly in the order people notice them.
- 1. A musty smell when the AC or heat turns on. The fan starts, air moves across mold on the coil or the duct wall, and the odor rides into the room. It eases off once the system stops.
- 2. Visible growth on or around the vent covers. Black, gray, or greenish specks on the register, the grille, or the ceiling right around a vent. What shows on the cover often has more behind it. Color won’t tell you what kind of mold it is, and it doesn’t need to: what “black mold” actually means.
- 3. Dust that’s back within hours of cleaning. Colonized ducts keep shedding particles, so nothing in the room stays clean for long.
- 4. A stuffy nose, sneezing, coughing, or itchy eyes in some people. The CDC lists a stuffy or runny nose, sore throat, coughing, wheezing, and itchy or watery eyes among the effects of being around mold (CDC, About Mold). Symptoms alone don’t prove there’s mold, and whether duct mold can make you sick is its own question.
- 5. A recent water event. A clogged condensate drain, a roof or pipe leak near the ductwork, or a flood. Mold needs moisture, and standing water in or near the system feeds it. What water damage does to ductwork has its own page.
- 6. Ducts that sweat. Beads of water on duct metal in a crawlspace, attic, or closet. The EPA illustrates this exact failure with a photo captioned “condensation on uninsulated air conditioning duct” (EPA, Mold Course Chapter 2).
- 7. A recent renovation. Renovation dust and new flooring load up the system, and Greg’s own Google reviewers mention a remodel in the same breath as the duct work. A new house can smell musty too. The age of the house doesn’t change where the smell comes from.
Any one of these can turn out to be something else, like a dirty filter or a dry drain trap. Two or more together, above all the smell plus specks on the covers, and duct mold is the likely answer.
Why does mold grow in air ducts in the first place?
Because of water. Mold in ducts is a moisture problem before it is a mold problem, and the EPA puts it in one line: “the key to mold control is moisture control” (EPA, A Brief Guide to Mold, Moisture and Your Home). Three things have to line up, and Lowcountry summers line them up all the time.
Cold surfaces in warm, wet air. Supply ducts carry chilled air, so the metal runs colder than the room around it. Warm humid air hits that metal and water condenses on it, the way a glass of iced tea sweats on a summer porch. The EPA names the same mechanism at the coil: “Research suggests that condensation (which occurs when a surface temperature is lower than the dew point temperature of the surrounding air) on or near cooling coils of air conditioning units is a major factor in moisture contamination of the system” (EPA, Should You Have the Air Ducts in Your Home Cleaned?). It recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent (EPA). The Charleston area stays humid about six months a year, late April into late October, with relative humidity about 72 percent on average (WeatherSpark climate summary for Charleston). For half the year we’re over the line.
Something for the mold to feed on. No duct is sterile. Dust, skin cells, pollen, and construction debris settle inside the runs. Add condensation and mold has both things it needs, water and organic matter, sitting in the dark where nobody looks.
Time and still air. A clogged condensate drain, an oversized system that short-cycles, or long stretches with the house closed up all let moisture sit. New, tightly built homes get it too. They run the AC in shorter bursts, which pulls less humidity out of the air, so moisture climbs (US Department of Energy Building Science, report BA-1310). That’s how a brand-new Cane Bay or Nexton home can smell musty within a couple of years. The detail is on why a brand-new home can smell musty.
Does your system need cleaning, treating, or replacing?
That depends on what the mold is growing on. Hard surfaces get cleaned and then treated. Porous material that got wet gets replaced, since there’s no surface to clean it back to. The EPA draws that line in writing, and which side of it you’re on decides who you call.
Hard surfaces: clean, then treat. Sheet metal duct, the registers, the cooling coil and the outside of the air handler are non-porous, so they can be cleaned back to the material and then treated. The EPA names “substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system” as one of its own reasons to have ducts cleaned (EPA, Should You Have the Air Ducts in Your Home Cleaned?). This is the work we do.
Wet or damaged porous material: replace it. Fiberglass duct board and the insulating liner inside a duct run can’t be cleaned back to a surface, because there is no surface, only fiber. The EPA says so directly: “If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced” (EPA, Should You Have the Air Ducts in Your Home Cleaned?). That is duct replacement. It belongs to an HVAC contractor, and when that’s what you’re looking at, we’ll say so instead of spraying over it.
Plain duct cleaning is a different job from treatment. A dust-only air duct cleaning runs a brush and vacuum through the runs and pulls out debris. It takes out dust, and it doesn’t replace treatment. When that truck pulls away, the mold on the coil and the duct wall is still there, and so is the moisture that fed it, which is why ducts can look clean and smell the same a few weeks later. Where cleaning stops and treatment starts.
The chemical goes on last, and only where it belongs. The EPA’s own instruction is to “Apply the biocide only to un-insulated areas of the duct system after proper cleaning, if necessary to reduce the chances for re-growth of mold” (EPA, Should You Have the Air Ducts in Your Home Cleaned?). Its caution about chemicals in ducts is aimed at fogging product into ductwork nobody cleaned first. So the system gets cleaned, and then the antimicrobial goes onto cleaned, un-insulated surfaces, applied to its label.
If water is still getting in, fix that first. “Controlling moisture is the most effective way to prevent biological growth in air ducts” (EPA, Should You Have the Air Ducts in Your Home Cleaned?). A live roof leak, a supply line that’s still weeping, or a condensate line that stopped draining is a roofer’s, a plumber’s or an HVAC contractor’s job before it’s ours. Treat the surface while the water runs and all you’ve bought is a few months.
On health. In the EPA’s words, “Duct cleaning has never been shown to actually prevent health problems” (EPA, Should You Have the Air Ducts in Your Home Cleaned?). What the work does is take away what the smell is growing on.
What does mold removal in air ducts cost?
Air duct cleaning and treatment is $50 a vent on the same visit as whole-home disinfection, as many vents as you have, with no extra minimum. Booked on its own, it’s $399 minimum. Whole-home disinfection is $0.30 per heated square foot with a $200 minimum, the same rate for a cottage or a four-bedroom. Both carry the 12-month written guarantee.
There’s no trip charge and no separate labor line on top. You pay on the day.
What the price covers:
- Every room inside the heated square feet you give us, closets included, and the garage when its footage is part of that number
- The air system, when the vents are on the job: the registers, the duct work, the coil and the outside of the air handler
- BactroKill Plus, an EPA-registered product, EPA Reg. No. 82972-1-90746, applied by the Bactronizing electrostatic process
- A 12-month written guarantee, excluding an area where new water has come in since, and a transferable treatment certificate that documents the work at resale
What this work costs around here, ours next to the national numbers. Air duct cleaning and treatment on its own is set out in full on its own page.
What is quoted separately from that price?
Three pieces of work, and two of them belong to other trades.
- Mold you can see on a wall or a ceiling. That’s a wipe-down. It gets looked at and quoted on its own, because no two are alike, and it isn’t priced per vent or by the house.
- Porous material that soaked. Fiberglass duct board, internal liner and wet insulation get removed and replaced by an HVAC contractor. We don’t treat them.
- A leak nobody has fixed yet. Fix the water, then treat the surfaces. Do it the other way round and you pay twice.
How long does it take, and can we stay home?
Yes, you can stay home. A whole-home visit runs about 30 minutes at 1,500 heated square feet, 45 at 2,500 and 75 at 3,500. A twelve-vent air system takes about 90 minutes on its own.
| The job | Time at the house |
|---|---|
| Whole house, 1,500 sq ft | About 30 minutes |
| Whole house, 2,500 sq ft | About 45 minutes |
| Whole house, 3,500 sq ft | About 75 minutes |
| Air system, 12 vents | About 90 minutes |
Keep people and pets out of a room while it’s sprayed, and it’s yours again 15 minutes later. The rest of the house is open to you the whole time.
How is mold in air ducts treated?
In four steps, and the order matters. Product sprayed over dirt just sits on the dirt, and a surface that’s still wet grows mold back.
- 1. Find the moisture. A cold duct sweating in humid air, a clogged condensate drain or a leak near the runs: whatever is feeding it gets found first, because if the water keeps coming, so does the mold.
- 2. Clean the system. Source removal across the registers, the duct work, the cooling coil, and the outside of the air handler. The growth comes off the surface before anything goes on it.
- 3. Apply the product. BactroKill Plus goes on to its label with an electrostatic sprayer, a process Bactronix calls Bactronizing. The sprayer charges the droplets so they wrap around a surface instead of landing only on the side facing the nozzle. That is how the back of a duct and the underside of a coil fin get covered at all.
- 4. Stand behind it. If what we treated comes back within 12 months, we come back and re-treat it at no charge. The one exclusion is an area where new water has come in since, because new water grows new mold. The guarantee is written on the invoice, and the treatment certificate transfers if you sell the house.
This is mold treatment. It is not structural mold remediation, and it doesn’t fix an active leak, which is why finding the water comes first. The room-by-room side of the job is set out on whole-home disinfection.
Mold in air ducts in Cane Bay, Summerville, and the Lowcountry
We treat mold in the HVAC systems of Cane Bay, Nexton, Carnes Crossroads, Summerville, Goose Creek, Moncks Corner, and the wider Charleston Lowcountry. Bactronix of the Lowcountry is owned by veteran Greg Busang.
- Mold treatment in Cane Bay, SC
- Mold treatment in Summerville, SC
- Selling a house with mold in the ducts
Request a window
Put your heated square feet in above, and a vent count if you want the air system done on the same visit. Pick the day and window that suit you, and we call or write back to lock in the time.