Duct cleaning: what to know

What the job involves, what changes the price, and what to ask a pro.

What duct cleaning is

Duct cleaning removes dust, pet hair and debris that build up inside the supply and return ducts and vents. A technician uses brushes and a powerful vacuum connected to the system, then seals the openings they used and checks the condition of the system while the ducts are open.

Signs you need it

  • Dust collects on furniture within a day or two of dusting, even with a clean filter in place.
  • You can see debris, lint or pet hair blowing out of the supply registers when the system starts.
  • There is visible dust or debris inside a register or on the first few feet of duct you can reach.
  • The house has had construction, a remodel or a fire, and the ducts were left open during the work.
  • Someone in the house has allergies or asthma that worsens when the system runs.
  • A musty smell comes from the vents, or you see what looks like mold on the duct surfaces or on the grilles.

What the pro does

  • Inspect the supply and return ducts with a camera or a light, and note any visible mold, pests, loose joints or damage.
  • Seal off the supply and return openings and set up a negative-pressure vacuum that pulls air through the system.
  • Agitate the duct walls with rotary brushes or air whips to loosen dust and debris from the surfaces.
  • Vacuum the debris out through the registers and the main trunk lines, then clean the register and return grilles.
  • Clean the supply plenum and the return air plenum where the duct lines meet the furnace or air handler.
  • Reseal the access points and check the system airflow when the cleaning is finished.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Number of supply and return lines, since each run must be cleaned and checked.
  • Length and layout of the ductwork, including any long runs or hard-to-reach branches.
  • Condition of the ducts, such as dust buildup, mold, crushed or disconnected sections.
  • Access to the ducts through the attic, crawl space, basement or walls.
  • Whether the air handler or furnace blower also needs cleaning as part of the job.
  • Whether the job includes sealing access openings, replacing registers or adding a return.
  • Whether mold remediation is needed, which is separate work from cleaning.

What a written quote should spell out

  • The number of supply and return runs cleaned, and the registers and grilles included.
  • The plenum and air handler areas cleaned, if included.
  • The camera or visual inspection results, with any mold, pests or damage listed.
  • Access openings sealed, and the sealing material used.
  • Post-cleaning airflow check or a written statement of the readings taken.
  • Any repair recommended, listed separately from the cleaning.

Questions to ask before you hire

  • Will you inspect the ducts with a camera before you start, and show me the photos afterward?
  • Do you clean the supply and the return, and do you clean the plenums and the blower area?
  • What negative-pressure equipment do you use, and how do you keep dust from spreading into other rooms?
  • What will you do if you find mold, and is that included in the quote?
  • How will you seal the access openings and the registers when the job is done?
  • Will you check the airflow after the cleaning and tell me the results?
  • What is the filter size for my system, and what do you recommend to keep the ducts cleaner?

Red flags

  • The pro offers a flat-rate duct cleaning that covers only the registers and does not reach the main trunk lines.
  • The pro says the ducts need cleaning but shows no camera inspection or photos of the dirt found.
  • The pro pushes sanitizing treatments or add-ons without explaining what they do or what they are for.
  • The pro leaves the access openings unsealed or the registers dusty when the job ends.

What you can do yourself

You can vacuum dust from the supply registers and return grilles, and clean the filter on the schedule the filter needs. Do not open the air handler or try to clean the ducts with a shop vacuum from the registers, since that spreads dust and can damage the system. Duct cleaning, plenum cleaning and mold work belong to a licensed contractor.

Licenses and permits

Duct cleaning is often done by licensed HVAC or cleaning contractors, and mold work may need a separate license. Check with your state or local licensing agency for the requirements that apply to the work in your area.

Duct cleaning questions

Does duct cleaning stop dust from coming back?

It removes what is in the ducts, but it cannot stop dust from entering. Keeping the filter changed and the home sealed reduces how fast dust comes back.

Is there mold in my ducts?

Mold inside ducts usually shows as dark spots, fuzz or a musty smell. A technician should look with a camera and test the source of any moisture before deciding how to clean it.

How do I know if my ducts need cleaning?

Look for visible debris in the registers, dust that returns quickly, pests or mold, and a musty smell from the vents. A camera inspection gives a clear answer.

Will duct cleaning lower my energy bills?

It can improve airflow when the ducts are badly blocked. In many homes, leaks, undersized ducts or a dirty coil have a bigger effect on energy use, so ask for an inspection along with the cleaning.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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