Questions to ask an air duct cleaning company before you hire

Updated November 10, 2026 · KeystoneProGuide editorial team

What should you ask a duct cleaning company first?

Ask what it found in your ducts that needs cleaning, and ask to see it. The U.S. Environmental Protection Agency (EPA) says to have any company that visits show you the contamination that would justify the work. Every other question follows from that one: what will be cleaned, how, with what, by whom, for how much, and how you will know it was done.

Use the list on the phone and again at the home visit. Answers are easier to compare when every company has been asked the same things.

What should you ask about whether the work is needed?

• What did you see, and can you show me? The EPA says many parts of a system cannot be seen without access, so ask to be shown any mold or debris a company says is there. Pictures from inside the ducts are one way. The EPA notes that some providers use remote photography to document conditions.
• If you think it is mold, how do you know? The EPA says only an expert can make a positive determination and that laboratory analysis may be needed. A petri dish left out to grow something is not evidence. The EPA calls that demonstration inappropriate, because some microorganisms are always present in the air.
• What caused it? The EPA says contamination usually has an underlying cause and that the cause must be corrected first, or the problem will likely come back.

What should you ask about what will be cleaned?

• Which parts of the system are included? The EPA treats the coils, heat exchanger, drain pans, fan and air handling unit as part of the job, not only the ducts and registers, and says leaving one contaminated component uncleaned can re-contaminate the rest. The full list is in what happens during an air duct cleaning.
• Is anything left out at this price? NADCA, the industry's trade association, says very cheap whole-house offers may leave out the air handler, blower fans, coils, registers or access openings.
• Will you cut access holes, and how will you close them? NADCA says technicians may need to cut openings in ductwork. The EPA says access holes should be sealed and re-insulated so they are airtight, and its checklist looks for access doors fixed with more than duct tape.
• What are my ducts made of, and how does that change the method? The EPA says cleaning methods differ for sheet metal, flexible duct, fiberglass duct board and fiberglass-lined ducts, and that only soft-bristled brushes should be used on fiberglass.

What should you ask about method and equipment?

• Does your vacuum exhaust outdoors, or is it HEPA filtered? The EPA says equipment should exhaust particles outside the home, or be HEPA equipment if it exhausts indoors. NADCA says the same of any collection device that vents inside.
• How do you loosen the debris? NADCA says a vacuum alone will not clean a system. Brushes, air whips or similar tools are needed, with the system held under negative pressure throughout.
• Will you check for asbestos before you start? The EPA says a provider should inspect for asbestos-containing materials, such as certain insulation or register boots, before cleaning, and that these should be left to specially trained and equipped contractors.
• How will you protect floors and furniture? The EPA says the provider should protect carpet and household furnishings during the work.

What should you ask about chemicals?

• Do you plan to apply any sanitizer, biocide, ozone or sealant? The EPA says not to allow chemical treatments unless you fully understand the pros and cons. If the answer is yes, ask to see the product label, ask which words on it cover use in ducts, and ask why brushing and moisture control will not do the job. NADCA says antimicrobial treatment is not part of a typical job for most homeowners.

What should you ask about the company?

• Are you a NADCA member, and who on this job holds the certification? NADCA certifies individuals, not companies, and says members must have at least one certified specialist on staff. Ask for the name, and check the membership in NADCA's directory.
• What is your Pennsylvania registration number? Registered home improvement contractors must show a number beginning with PA on estimates and contracts, and it can be looked up in the Attorney General's contractor search. The Pennsylvania rules guide explains what the state's guidance does and does not say about duct cleaners.
• Can you show proof of insurance and give references? NADCA advises getting proof of insurance. The EPA says to check that past customers had no problems with their systems afterwards.
• Have you worked on a system like mine? The EPA says to confirm it.

What should you ask about price and time?

• How is the price calculated? HomeAdvisor lists four models: a flat fee plus a charge per vent, a charge per vent, a trip fee plus a charge per vent, and a charge per square foot. Ask which applies and what was counted.
• What will the total be, in writing? The EPA says to get a written agreement stating the total cost and scope before work begins.
• How long will it take, and how many people will come? NADCA says a contractor should be able to give a general time estimate in a first phone call. If the price is hourly, the EPA says to ask for an estimate of the hours or days.

What should you ask about the finish?

• How will you show me the system is clean? The EPA says a thorough visual inspection is the best check, and it publishes a post-cleaning checklist that it suggests showing to the company before work begins. NADCA says that if any dust or debris can be seen, the system should not be considered cleaned.
• What happens if it is not? The EPA says to ask the provider to correct any deficiencies until every item on its checklist can be answered yes. Get the company's answer to this before you book, not after.

What do you do with the answers?

Write them down next to each company's quote, so that three companies can be compared answer by answer. The questions about need and about the finish go to the heart of the EPA's guidance: what was found, what caused it, and how the result will be shown to you.

A company that will not say what it found, or answers with a health claim, has given you a reason to stop. The EPA says not to hire duct cleaners who make sweeping claims about health benefits or who recommend duct cleaning as routine maintenance.

For the wider process of comparing companies, see how to choose an air duct cleaning company. Businesses are listed on the air duct cleaning directory page.

Sources

1. Should You Have the Air Ducts in Your Home Cleaned?, U.S. Environmental Protection Agency
2. Why Hire a NADCA Member?, National Air Duct Cleaners Association (NADCA)
3. FAQs, National Air Duct Cleaners Association (NADCA)
4. Cost & Time Estimates, National Air Duct Cleaners Association (NADCA)
5. Air Systems Cleaning Specialist (ASCS), National Air Duct Cleaners Association (NADCA)
6. Frequently Asked Questions, National Air Duct Cleaners Association (NADCA)
7. Frequently Asked Questions: Home Improvement Contractor Registration, Pennsylvania Office of Attorney General
8. Home Improvement Contractor Search, Pennsylvania Office of Attorney General
9. How Much Does Air Duct Cleaning Cost in 2026?, HomeAdvisor