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Heavy black and grey mold growth spreading across an interior wall

That Musty Smell When the AC Kicks On Is Usually Mold in Your Vents

How much for your vents?

HVAC mold treatment at $50 a vent, $399 minimum, with a 12-month guarantee. Add the dryer vent for $99.

Put your vent count in above and the total appears here.

Backed by a 12-month guarantee.

Leave your number and we will call you with the price for your house.

The short answer

We treat it at every vent for $50, $399 minimum, with a 12-month guarantee. Removing mold from inside an HVAC system runs $2,000 to $10,000 nationally (HomeGuide 2026, This Old House 2026). This is the affordable fix before it gets there. Bactronix is Marine-owned: Greg Busang sets the flat price you see here and stands behind every job his crews finish.

A Bactronix technician in a full protective suit, respirator and gloves, holding a pump sprayer beside a house with foundation vents in the wall behind

Call now: 843-282-7777

Marine veteran owned · EPA-registered antimicrobial · 12-month guarantee · Flat $50 per vent, $399 minimum, posted price


You have heard the air duct horror stories.

That is why most people never call. We do it the opposite way. One flat price, $50 a vent with a $399 minimum, posted right here on the page. Greg Busang owns the company and set that number himself; the crews he trained work to it, so nobody standing at your vents earns a dime by inflating it. You see the exact math before you pick up the phone.


See your price in 30 seconds.

Enter your vent count. The price is the vent count and nothing else. If the crew counts a different number at the door, it moves by $50 for each vent, either way, and they tell you the count and the total before they start. No trip charge, no call-out fee, nothing for the quote.


How much does it cost to treat mold in your HVAC vents?

Mold treatment runs $50 per vent, flat, with a $399 minimum job. A typical 10 to 15 vent home is $500 to $750, 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.

Scope of work Price
Bactronix per-vent treatment $50 per vent (flat, $399 minimum)
Typical 10 to 15 vent home $500 to $750
Conventional HVAC-system mold removal $2,000 to $10,000 (national estimate, Charleston SC area: HomeGuide 2026, This Old House 2026)
Whole-home mold remediation $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, coil, drain pan, and 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.

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.

A Bactronix technician applying treatment with the company's electrostatic sprayer along rows of seating in a large auditorium

Is duct cleaning the same as mold treatment?

No. Duct cleaning moves dust. It does not treat the mold growing on the coil and duct surfaces, and cheap cleanings skip sanitation entirely. Treatment cleans the system, then applies an EPA-registered antimicrobial to every surface. That is the step that actually kills the mold.

A standard duct cleaning gets the loose debris out. It does nothing for the colony on the cold coil or the slime in the drain pan, 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.


Is it safe to put antimicrobial in my air ducts?

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. That is the difference between a treatment and a spray bottle.


Cane Bay and Summerville air is built for duct mold.

Mold around a home window from indoor humidity
  • It is muggy here about six months a year. The Charleston and Summerville area sits humid from late April into late October, with average relative humidity around 72 percent (WeatherSpark; weather-and-climate.com). The EPA says mold grows when indoor humidity climbs over 60 percent, and recommends keeping it between 30 and 50 percent (EPA). We sit above that line for half the year.
  • Your AC duct is the coldest surface in the house. Warm, wet Lowcountry air hits that cold metal and condenses. The EPA literally illustrates this with a photo captioned “condensation on uninsulated air conditioning duct” (EPA, Mold Course Chapter 2). That water, plus the dust already in the duct, is mold food, sitting right where your air blows out.
  • A house that still feels new is old enough to have this. Cane Bay, Nexton and Carnes Crossroads are recent subdivisions, not old neighborhoods, and the humidity above is the same humidity. If nobody has ever cleaned the ducts, the age of the house does not protect them. If your house smells musty, it is not in your head, and it is not a defect you caused.

You smell it before you see it.

Heavy mold spread across an interior wall at a Bactronix job, with the wall framing exposed beyond it
A young child on a living room floor, illustrating why indoor air quality matters for families

Mold in the system does not stay in the system. Every time the blower runs, it pushes spores back into the bedrooms. For some people that means a stuffy nose, coughing, wheezing, or itchy, watery eyes, and people with asthma or a mold allergy can react more strongly (CDC; EPA). You do not have to see black spots on a vent for the air to be the problem. The smell when the AC starts is usually the first and only sign.


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 sneezing or a cough that eases when you leave, dust that returns within hours of cleaning, a recent water event, or a new home. A short on-site check confirms it.

Signs it is mold in your system, not just a dirty filter:

  1. A musty or earthy smell that shows up when the AC or heat kicks on.
  2. A stuffy nose or a cough that eases within hours of leaving the house.
  3. Dust or fine debris that returns on surfaces within a day of cleaning.
  4. Visible specks or fuzz on or around the vent covers and registers.
  5. A recent leak, flood, or long humid stretch with the system running little.
  6. Ductwork that has never been cleaned, however new the house still feels.

Every $50-a-vent, $399-minimum treatment covers the whole system.

Flat $50 a vent, $399 minimum job. Here is what that buys:

  • Every supply and return vent, register, and grille
  • Heating and cooling coil
  • Condensate drain pan
  • Blower motor and fan housing
  • Air handler cabinet
  • EPA-registered antimicrobial, applied by the Bactronizing electrostatic process
  • A 12-month guarantee
  • 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.

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. Those first three sit at the center of the route map, so they usually get the earliest openings.

Find your area or the answer to your question:


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, the drain pan, or the duct near the air handler. Humid Lowcountry air condenses on those cold surfaces and feeds it. A $50-per-vent treatment ($399 minimum) treats the source.

Can mold in air vents make you sick?

It can affect some people. The CDC notes mold can cause a stuffy or runny nose, sore throat, coughing, wheezing, and itchy or watery eyes, and that people with asthma or a mold allergy may react more strongly. The blower recirculates it 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. A typical 10 to 15 vent home is $500 to $750, 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.

Is it safe to put antimicrobial in my air ducts?

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 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 sneezing or a cough that eases when you leave the house, dust that returns within hours of cleaning, a recent water event, or a new home. A short on-site check confirms it.


Book your treatment.

Tell us the times that work and we call you back to lock one in. Booking costs nothing. The crew counts your vents at the door and tells you the count and the total before they start, and the total moves by $50 a vent, either way, and by nothing else.

Or call 843-282-7777, Monday to Friday 8 to 4, Saturday 8 to noon.

Book online or see your price first.

Marine veteran owned. EPA-registered products. 12-month guarantee. Flat $50 per vent, $399 minimum, posted price.

Where to next

How the treatment works

The full walk through of what happens to an HVAC system, start to finish.

Areas we serve

Find the page for your town and what the schedule looks like there.

Every service

Testing, treatment, duct cleaning, dryer vents and disinfectant work.

$50 a vent, $399 minimum, 12-month guarantee.

Call 843-282-7777Book