Mold in air ducts: what Little Rock homeowners should know

Black specks around a ceiling vent, a musty blast when the AC kicks on, a duct cleaning coupon in the mailbox promising cleaner air. Mold in air ducts is a real problem in some Central Arkansas houses and an easy upsell in others. This page covers how to tell which one you have, what removing it actually takes, and where the U.S. EPA draws the line.

Why ductwork gets wet around Little Rock

Most houses here run their supply ducts through a vented crawl space or a hot attic, which puts the coldest air in the house right next to some of the muggiest air in the country. Average July dew points at the Little Rock airport run about 71°F (humidity and dew point by month), and a supply duct carrying air-conditioned air is far colder than that. Any spot where the duct wrap is torn, a joint has pulled apart, or a register boot isn't sealed to the ceiling becomes a cold surface that collects water. EPA's guide on whether to have your air ducts cleaned says condensation on or near the cooling coil is a major factor in moisture getting into the system, and that condensation or high humidity is an important sign that mold can grow on any type of duct.

Other common sources EPA lists: a condensate pan that holds standing water instead of draining, wet insulation near the coil, plumbing or roof leaks that reach the ducts, and an air conditioner that's too large for the house, which cycles on and off quickly and pulls little moisture out of the air.

Is it really mold in the ducts?

EPA's advice is to be skeptical until you see it. Much of a heating and cooling system can't be inspected visually, so ask anyone who says your ducts are moldy to show you where. Something that looks like mold may not be; a firm answer can take an expert and a lab. A dusty return grille is normal, because the return pulls air through it all day; it can be vacuumed or washed. Dark spotting on the face of a supply register in summer usually means the register itself is sweating, which points back to humidity in the house or a leaky boot behind it, not necessarily growth deep inside the duct run. A mold inspector in Little Rock who checks the air handler and accessible ductwork can sort this out before anyone quotes a cleaning.

What duct mold removal involves

What can be done depends on what your ducts are made of. EPA's guidance breaks down like this:

A proper cleaning opens access ports so the whole system can be reached, uses vacuum equipment that exhausts outdoors or through HEPA filters, and covers every component, not just the ducts: coils, drain pan, blower and housing. EPA warns that skipping one contaminated component can re-contaminate the rest. It also says to check for asbestos-containing materials (old register boots or duct insulation) before cleaning starts, since those need specially trained contractors. The industry standard most companies work from is NADCA's ACR standard for assessment, cleaning and restoration of HVAC systems.

Biocides, foggers and duct "sealants"

Duct cleaners often offer to spray a biocide to kill mold or coat the inside of the ducts with a sealant. EPA's position is that these treatments haven't been fully researched for effectiveness or health effects, that they should go on only after the system has been cleaned, if at all, and that no chemical biocides are registered by EPA for use in internally insulated duct systems. Coating the inside of a duct is also a different thing from sealing its leaks. Sealing leaky joints with mastic does help: it stops humid crawl space or attic air from getting in and saves energy.

Cleaning the ducts versus fixing the cause

EPA says plainly that unless the cause is corrected first, mold in a duct system will come back. Around Little Rock the cause is usually one of these, and most are HVAC repairs rather than cleaning jobs:

• Duct joints and boots that leak, or duct wrap that is torn or missing, in a crawl space or attic.
• A clogged or poorly sloped condensate pan or drain line at the air handler.
• An oversized system that short-cycles and leaves the house clammy.
• A crawl space or attic that stays humid all summer. Drying the space under the house with a vapor barrier or encapsulation takes away the wet air the ducts are sitting in.

If mold has spread beyond the ducts to the subfloor, joists or drywall around the registers, that part is mold remediation work and needs containment and removal, not just a duct vacuum. Crawl space growth around the duct runs is covered in crawl space and attic mold.

Air duct cleaning in Little Rock: when it helps with mold

Duct cleaning gets sold as routine upkeep, but EPA does not recommend cleaning ducts routinely, only as needed, and says cleaning has never been shown to actually prevent health problems. It does list when cleaning is worth considering: substantial visible mold growth inside hard-surface (sheet metal) ducts or on other parts of the heating and cooling system, ducts infested with rodents or insects, and ducts clogged with so much dust and debris that it is coming out of the supply registers.

Two limits matter for a mold job. First, insulated duct that has gotten wet or moldy cannot be effectively cleaned; EPA says it should be removed and replaced, which is why wet fiberglass duct board and lined duct get swapped out rather than scrubbed. Second, the cause has to be fixed before anyone cleans, retrofits or replaces anything. In Little Rock that usually means a sweating duct, a bad condensate drain or a humid crawl space, and if it is not corrected, EPA says the growth will recur.

If you ask a company for a duct cleaning quote, a written scope should say which parts of the system are included (ducts, coil, drain pan, blower), where the access ports will be cut, how the dust is captured, and what happens to any lined or wet duct they find. We handle duct cleaning when mold or moisture is the reason; call us and tell us what you have seen at the registers or the air handler.

Before you hire anyone for duct mold

• Ask them to show you the mold, in photos or in person, before you agree to anything.
• Get at least three written estimates with the full scope and cost, as EPA suggests, and be wary of anyone promising health benefits or selling duct cleaning as routine yearly maintenance.
• Ask what state license they hold. EPA's guide listed Arkansas among the states that required air duct cleaners to be specially licensed, and heating and air work is licensed by the state's HVACR Licensing Board, which has a separate Class D license for ductwork sheet metal. Ask for the license number.
• Ask whether they follow the NADCA standard and how they'll handle fiberglass-lined or flex duct.
• Afterward, look for yourself: a flashlight shone into the cooling coil should come through the other side, the drain pan should be clean and draining, and new access doors should be fastened with screws or mastic, not just duct tape.

If the inspection shows the problem has spread past the HVAC system, our checklist for comparing mold removal services in Little Rock covers what to ask. Or call us about duct and air handler mold in Little Rock, North Little Rock, Conway, Benton and the rest of Central Arkansas.