A musty smell from the vents when the AC starts usually means mold or mildew inside the air system. We scrub each vent and return with a rotary brush, clean the registers, coil and air handler exterior, then treat them with BactroKill Plus, an EPA-registered product. It is $50 a vent with a $399 minimum, or $50 a vent with no minimum when added to a whole-home disinfection. Every job carries a 12-month written guarantee.
Bactronix of the Lowcountry is owned by Greg Busang. Veteran owned. Licensed and insured.
What you see here is what you pay
$50 a vent. Every vent and every return counts as one. Vents booked on their own start at $399. Put the count in above and you see your price before anyone comes out.
$399 minimum when vents are the only job. That covers seven vents or fewer. Add the vents to a whole-home disinfection and it is $50 a vent, however many you have, with no $399 minimum. Most people with growth in the vents do both: spores travel on the air, so what is in the duct work has been through the house.
$50 dryer vent. Added to a treatment visit it is $50. Booked on its own it is $99. It is the only add-on we post.
12-month written guarantee. It goes on the invoice. If what we treated comes back inside the year, we come back and re-treat it.
How to count your vents
- Walk every room with the system running. Include hallways, closets and the laundry room.
- Count every register: the ones that blow air (supply) and the ones that pull it back (return). Each one is a vent.
- Put that count in above. Under eight vents the job is $399, and you see that before anyone comes to the house.
Not ready to walk the house tonight? Most homes run about one vent for every 150 to 200 heated square feet, so a 1,900 square foot house is usually 10 to 13 vents, and a 2,500 is usually 13 to 17. That is a rough guide and not a quote. Your own count sets the price.
How much does it cost to treat mold in your HVAC vents?
Air duct cleaning and treatment runs $50 per vent, flat, with a $399 minimum job. Ten vents is $500, fifteen is $750, and every job is guaranteed for 12 months. Conventional mold removal inside an HVAC system runs $2,000 to $10,000 nationally (HomeGuide 2026, This Old House 2026). We treat it early, before it gets there.
What the price covers, on every job:
- Every supply and return vent, register and grille, the inside of each one scrubbed with a rotary brush
- The duct work
- The heating and cooling coil
- The outside of the air handler
- A product that does not stain or bleach materials or fabrics and will not harm HVAC system components. Nothing needs rinsing afterward.
- A transferable treatment certificate. If you sell, it documents for the buyer that the air system was cleaned and treated, the one part of the house a South Carolina CL100 letter never grades.
| Scope of work | Price |
|---|---|
| Bactronix per-air duct cleaning and treatment | $50 per vent (flat, $399 minimum) |
| 10 to 15 vents | $500 to $750 |
| Conventional HVAC-system mold removal | $2,000 to $10,000 (national estimate, Charleston SC area: HomeGuide 2026, This Old House 2026) |
| Structural mold remediation, a different job | $1,200 to $3,750+ (national estimate, Charleston SC area) |
The $2,000 to $10,000 band is for removing mold from inside an HVAC system, not plain duct cleaning. Routine per-vent duct cleaning runs $25 to $50 a vent nationally. Our $50 a vent, with a $399 minimum, is antimicrobial treatment, the step those cheaper cleanings skip. Sources: HomeGuide 2026, This Old House 2026, Angi 2026.
How do you actually treat mold in air vents?
We find the moisture feeding it, clean the mold off every surface in the system, then apply an EPA-registered antimicrobial by electrostatic process so it coats what a brush cannot reach. The EPA is blunt: the key to mold control is moisture control. We back it 12 months.
1. We find the moisture. Mold in ducts is a water problem first. The EPA says it plainly: “the key to mold control is moisture control” (EPA, A Brief Guide to Mold, Moisture and Your Home). We locate what is feeding it, usually a cold duct sweating in humid air.
2. We clean the system. Source removal across the supply runs, returns, registers, the duct work, the coil and the outside of the air handler. You cannot treat mold you have not cleaned off.
3. We apply the antimicrobial. An EPA-registered antimicrobial, applied to its label, by our Bactronizing electrostatic process so it coats every surface the brush cannot reach. Keep people and pets out of the room while we spray it, and it is yours again fifteen minutes later.
4. We stand behind it for 12 months. If the treated mold comes back inside a year, we come back and re-treat it. No charge.
Is duct cleaning the same as mold treatment?
No. Plain air duct cleaning removes dust. It does not treat the coil and duct surfaces, so it does not replace treatment. Air duct cleaning and treatment cleans the system, then applies an EPA-registered antimicrobial to every surface. That is the step a cleaning skips.
A standard duct cleaning gets the loose debris out. It does nothing for the colony on the cold coil or the film on the duct surfaces, which is where the musty smell comes from. That is why a cleaning alone often leaves the smell behind. Treatment is the cleaning plus the antimicrobial step, applied to the source.
Should an antimicrobial go into my ducts at all?
The EPA cautions against fogging biocide into dirty ducts, and we agree. We do the opposite. We clean the system first, fix the moisture feeding the mold, then apply only an EPA-registered product to its label. Used that way, after cleaning, it is an established treatment, not a shortcut.
The EPA’s “Should You Have the Air Ducts in Your Home Cleaned?” raises a fair question about chemical biocides in ductwork. Spraying biocide over uncleaned ducts, without fixing the water, is exactly why other companies’ “mold treatments” do not hold. We clean first, treat the source of the moisture, and use the product the way its label requires.
What people were quoted, and what they paid
Two of these are from public reviews of other companies working in this market.
| Told | Invoiced | Moved | |
|---|---|---|---|
| One company in this market | $150 | $400 | Up $250 |
| Another company in this market | About $600 | $1,477 | Up $877 |
| Bactronix, 12 vents | $600 | $600 | Did not move |
The two stories are quoted from two public Google reviews of Charleston-area cleaning companies, read 2026-09-02. The companies are not named here. Our row is the arithmetic on 12 vents at $50 a vent, above the $399 minimum.
Who turns up
A white van with the phone number on the side, and Greg’s own people in it. If the musty smell comes back when the air runs inside the year, call that number and we come back.
Veteran owned. Licensed and insured. EPA-registered product. 12-month written guarantee.
How do I know if I have mold in my ducts?
The most common sign is a musty smell when the HVAC runs, even with nothing visible on the vents. Watch for dust that returns within hours of cleaning or a recent water event. A short on-site check confirms it.
You do not have to see black spots on a vent for the system to be the problem. Most of what grows is on the coil, in the drain pan and in the first stretch of duct, where you cannot see it. The smell when the AC starts is usually the first and only sign.
Signs it is mold in your system, not just a dirty filter:
- A musty or earthy smell that shows up when the AC or heat starts running.
- Dust or fine debris that returns on surfaces within hours of cleaning.
- Visible specks or fuzz on or around the vent covers and registers.
- A recent leak, flood, or long humid stretch with the system running little.
- Ductwork that has never been cleaned, however new the house still feels.
We start in our own backyard.
We treat HVAC mold across Cane Bay, Nexton, Carnes Crossroads, Summerville, Goose Creek, and Moncks Corner, plus the wider Charleston Lowcountry. The route map starts in those first three. It is muggy here from late April into late October, with relative humidity about 72 percent on average (WeatherSpark climate summary for Charleston), and the EPA says mold grows when indoor humidity climbs over 60 percent (EPA, A Brief Guide to Mold, Moisture and Your Home).
Find your area or the answer to your question:
- Mold treatment in Cane Bay, Nexton and Carnes Crossroads
- Mold treatment in Summerville SC
- Why does my AC smell musty when it turns on?
- What does it really cost to treat mold in your HVAC?
- Why does my brand-new Cane Bay home smell musty?
- Mold in air ducts: signs, causes, cost, and treatment
- Can mold in your air vents make you sick?
- Mold in air ducts after water damage
- Selling a house with mold in the ducts in SC
- HVAC mold across a portfolio: the property manager’s guide
Frequently asked questions
Why does my AC smell musty when it turns on?
A musty smell when the AC starts almost always means mold or mildew inside the system, usually on the cooling coil or the duct near the air handler. Humid Lowcountry air condenses on those cold surfaces and feeds it. A $50-per-air duct cleaning and treatment ($399 minimum) treats the source.
Can mold in air vents make you sick?
It depends on the person. The CDC says exposure to damp and moldy environments may cause a variety of health effects, or none at all, and that for some people mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or a skin rash. The HVAC system recirculates the air through the house, so treating the system removes that source.
How much does it cost to treat mold in HVAC vents?
Bactronix treats the mold in your HVAC system for a flat $50 per vent, with a $399 minimum, guaranteed 12 months. National sources price mold removal inside an HVAC system at $2,000 to $10,000 (HomeGuide 2026; This Old House 2026).
Is duct cleaning the same as mold treatment?
No. Standard duct cleaning moves dust. It does not treat the mold growing on the coil and duct surfaces, and a lot of cheap cleanings skip sanitation entirely. Our service cleans the system, then applies an EPA-registered antimicrobial to every surface. That is what actually treats the mold, so we call it treatment.
Should an antimicrobial go into my ducts at all?
The EPA cautions homeowners not to let a company simply fog chemical biocide into dirty ductwork, and we agree. We do the opposite of a spray-and-go. We clean first, address the moisture feeding the mold, and apply only an EPA-registered product to its label. Used that way, it is an established treatment.
How often do ducts need cleaning?
About every four years, in Greg’s experience. Pets, a smoker or a system that has been wet shorten that. Once we have cleaned a system, a yearly vents-only re-treatment with no cleaning is available to customers as maintenance, priced when we see the system; a vent with dust or growth in it needs the cleaning first, because spraying does not take that off.
How do I know if I have mold in my ducts?
The most common sign is a musty smell when the HVAC runs, even when you cannot see anything on the vents. Others include dust that returns within hours of cleaning and a recent water event. A short on-site check confirms it.
Request a window
Put your vent count in at the top of this page and the price comes back. Pick the day and window that suit you. We call or write back to lock in the time.