Independent guide · we don’t clean ducts

Questions to Ask an Air Duct Cleaning Company

Direct answer

Ask nine things before you agree to duct cleaning: will the whole system be inspected before you are quoted; exactly which components are included and excluded; how the price is calculated and whether per-vent charges can be added later; whether the advertised price is the price you will pay; what equipment will be used; whether you can see inside the system before and after; whether any chemical is proposed and what its label says; what insurance and credentials can be verified; and what happens if they find something unexpected.

How to use this framework

This is a scoring tool, not a script to read aloud. Each question below comes with what a good answer sounds like and what a bad answer sounds like, so you can judge a response as you hear it rather than afterward.

Three rules make it work:

  1. Ask before the visit. The mechanism documented in state enforcement cases is not a bad phone call; it is a low advertised price used to place technicians inside the home, where declining becomes socially expensive. One homeowner in a Northwest news investigation described being alone with her children and feeling “cornered and pressured.” Everything below is answerable by phone.
  2. Write down the answers. You are comparing companies, and a written record turns “he said something about the coils” into a comparison you can actually make.
  3. Ask the same questions of everyone. Two quotes that sound different often describe different jobs. The point of a fixed question set is to find out which.

A bad answer is not proof of a bad company

Small firms with good technicians sometimes have poor phone habits, and a vague answer can just mean you reached the wrong person. Ask for the answer in writing before you decide. What should end a conversation is a refusal to put anything in writing at all.

The nine questions

Each question, what a good answer sounds like, and what a bad answer sounds like
Ask thisA good answer sounds likeA bad answer sounds like
1. Will you inspect the entire system before giving me a price? “Yes. We look at the supply and return runs, open the air handler, and check the coil and blower before we quote. If you want a phone estimate first, it is provisional and I will tell you what could change it.” Offering to inspect and showing you what they find matches the EPA’s own test for whether cleaning is needed, which rests on visual inspection. “We don’t need to see it, it’s the same job in every house.” Or a firm price quoted sight-unseen with no stated assumptions. A price given without looking is a price for a product, not for your system — and it leaves the actual scope to be discovered on the day.
2. Exactly which components are included — and which are excluded? A component-by-component answer: supply ducts, return ducts, plenum, air handler cabinet, blower, evaporator coil, registers and grilles, each named as in or out, plus whether cutting and resealing access openings is included. “The coil is not included; it is $X extra if you want it” is a good answer. “Everything,” or “the whole system,” with no list. NADCA warns that extremely low-cost whole-house specials often cover only limited portions of the system and may exclude the air handler, blower fans, coils, registers, or the access openings needed to do the work. In one Washington case, the advertisements omitted that only half the heating and cooling system was included.
3. How is the price calculated, and can per-vent charges be added later? “We price per system. Your house has one system, 14 supplies and 2 returns, and the total is $X. If we find more vents than counted, they are $Y each and I will call you before doing them.” Any model — per system, per vent, per square foot, hourly — is fine if the unit and the unit rate are both stated. “It depends what we find,” with no rate attached. Or an advertised whole-house price with an unstated vent limit. One Denver company advertised $242 for a “whole house air duct and carpet cleaning” whose fine print limited it to 5 rooms and 10 vents; the owner conceded “It is not the whole house.”
4. Is the advertised price the price I will pay? “For a standard single-system home with up to N vents, yes, and I will email that in writing before we come. Anything beyond that scope is quoted and approved before we start.” A willingness to put the advertised number in a written estimate is the whole test. “That’s a starting price.” Or a claimed discount from a “regular” price. In two states the companies were found never to have sold at the regular price their coupons claimed to discount — the Oregon complaint states: “Defendants have never sold the advertised service for $169 or $225.” Documented outcomes include $35 advertised turning into $1,000 charged in Colorado, and $49 specials producing bills up to $3,000 in Missouri.
5. What equipment and method will you use? Named equipment and named method: a truck-mounted or portable HEPA collection unit creating negative pressure in the duct, plus mechanical agitation such as a rotary brush or an air whip, with access openings cut and properly sealed afterward. A company that answers this fluently has done the work. “We use a really powerful vacuum,” with no mention of negative pressure, agitation, or access. Also disqualifying: any mention of steam or another moisture-introducing method, which should never be used on ductwork. Work performed only through the register openings is the “blow-and-go” pattern that NADCA and the Michigan Attorney General both warn about.
6. Will you show me the system before you start and after you finish? “Yes — we will open a section and show you, and we will show you the same section at the end.” The EPA frames the decision to clean as resting on visual inspection, which makes seeing inside your own system an entitlement rather than a favor. Deflection: “there’s nothing to see,” or photographs you cannot match to your own house. If images are offered, ask to be present when they are taken. One archived Illinois lawsuit alleges misuse of before-and-after photographs; we cannot verify it beyond that single filing, but being present costs nothing.
7. Are you proposing any chemical, sanitizer, or antimicrobial — and may I see the label? “No chemical is included, and we don’t recommend one for a system like yours.” Or, if one is proposed: the product named on the estimate, its EPA registration number, the surfaces its label approves, and a straight answer about what your duct material actually is. Showing you the label is the correct response. “We fog everything, it kills mold and bacteria.” A small number of products are EPA-registered specifically for the inside of bare sheet metal ducts, and no product is registered as a biocide for fiberglass duct board or fiberglass-lined ducts. Using a pesticide inconsistently with its label directions violates federal law. Oregon alleged a sanitizing spray charged from $1 to over $300 and the same UV light sold at $40 and $775.
8. What is your legal business name, and what registration, insurance and credentials can I verify? The full legal entity name, physical address, a certificate of insurance you can confirm with the carrier, and a straight answer to “what registration or license applies to this work in my state, and can you show me yours?” A good answer names the scheme — a home improvement contractor registration, a mechanical or HVAC contractor license where the work opens up the system — rather than waving at a certificate. If NADCA membership is claimed, the exact name to search in the association’s directory. A brand name only, a logo instead of a certificate, or irritation at being asked. Also weak: “duct cleaning is licensed in this state, that’s why we’re the safe choice,” which is a claim to check with the state rather than to accept. NADCA warns that some companies illegally use its logo or falsely claim membership. A Colorado action involved companies telling courts they had closed then reopening under new names, and a New Jersey action charged duct cleaning operators with failing to register as home improvement contractors.
9. What happens if you find something unexpected? “We stop, show you, quote it in writing, and you decide. Nothing extra gets done without your approval.” A stated change-order process, plus a willingness to say that a finding might mean you should call a different trade instead. A finding announced mid-job with a same-day price and a reason to decide now. NADCA specifically names being told without proper inspection that mold or another dangerous substance is present as a red flag, and a Better Business Bureau warning described technicians “discovering” mold, bacteria, or furnace problems and pressing for immediate purchase.

Why each question exists

The table is the tool. This section is why it is built that way, so you can improvise when a call goes somewhere the table does not cover.

Questions 1 and 2 decide everything else

Inspection and component scope are upstream of price. If nobody looked, and if the component list is missing, then every number discussed afterward is provisional whether or not anyone says so. The single most common structural defect in duct cleaning advertising is a headline price attached to an unstated scope. That is what the Better Business Bureau found in Denver when it studied 62 companies and asked 21 of them to change their advertising Verified fact — and notably, 18 complied and no fraud was alleged. Bad advertising is common; fraud is not.

Questions 3 and 4 are where money is actually lost

Four pricing models are in real use: per system, per vent or register, per square foot, and hourly. None is dishonest. What matters is that the unit and the rate are both named, and that any overage rate is agreed before the work rather than presented after it.

For calibration: published per-supply-vent pricing runs $25 to $50, with $35 the modal figure, and returns typically run higher at $40 to $75 Typical range. Full-scope per-system cleaning is published at $450 to $1,000 Single source, though the EPA document carrying that figure has not changed it since at least January 2021 and has never inflation-adjusted it. Homeowners report paying around $389 Single source — a number that appears in five publications drawing on one dataset. Our own planning range for a typical accessible single-system home is $300 to $700 Editorial estimate. Our calculator converts a vent count into a range you can hold a quote against, and the audit of where those published figures come from explains why they disagree.

Question 5 separates the trade from the theater

Duct cleaning that works removes debris from the duct into a collection unit rather than into your living space. That means negative pressure inside the duct, mechanical agitation to release material from the duct walls, and physical access to the runs. A vacuum held at a register does none of those things well. The Michigan Attorney General’s warning describes exactly what the failure looks like from the homeowner’s side: dirt blown onto drapes, carpets, and furniture. There is no official duration to hold a shortcut against — no agency or standards body publishes one — but Consumer Reports put a quality job at two technicians for about 8 to 15 hours in February 2008 Single source, which is the only such figure we found and is worth knowing before you accept a one-hour visit as normal.

Question 6 is your leverage, not your suspicion

Asking to see inside your own duct system is not an accusation. The EPA’s guidance says the way to know whether cleaning is needed is a visual inspection, and that if inspection shows no large deposits of dust or mold, cleaning is probably unnecessary. That makes “show me” the natural first step, before and after. It also gives you the option of concluding that you do not need the service — the cheapest outcome available. Our page on whether you need duct cleaning covers the three conditions the EPA identifies.

Be specific about what “show me” means, though, because the standard offer is two photographs and those establish very little. Ask for the same identified location, opened in front of you, at the start and at the end. What a photo pair does and does not prove sets out the difference between that and a picture you cannot match to your own house.

Question 7 has the clearest right answer on this page

The federal position is specific enough to be checked at the door. A small number of products are EPA-registered specifically for use on the inside of bare sheet metal ducts. No products are currently registered by the EPA as biocides for use on fiberglass duct board or fiberglass-lined ducts. A general “hard, non-porous surfaces” claim on a label does not extend to HVAC components unless HVAC use is specifically included on that label, and applying a pesticide product inconsistently with its label directions violates federal law. Verified fact

So the sequence is: establish your duct material, then look at the label. Antimicrobial fogging of a fiberglass-lined system has no EPA-registered basis. Related: the EPA notes that it, NADCA, and two other industry bodies do not currently recommend routine use of sealants to encapsulate contaminants in any type of duct — so an offer to “seal in” contamination is against the joint guidance of the regulator and the industry alike. We go through the full picture in the sanitizing and biocide section of our scams page.

Question 8 has a better version than “are you licensed”

We read the contractor licensing rules of eight states — California, Florida, Texas, New Jersey, Michigan, Arizona, Washington, and Hawaii — and none of them licenses air duct cleaning as a trade of its own Verified fact. Hawaii lists 68 specialty classifications and California 47, and the trade is absent from both. So “are you licensed?” invites a yes that means very little.

The version worth asking is “what registration or license applies to this work in my state, and can you show me yours?” Where a requirement reaches duct cleaning, it reaches it by absorption into some other scheme, and the three we verified are answerable questions:

  • Home improvement contractor registration. New Jersey’s regulation lists central heating and air conditioning equipment among covered work, and its 2011 enforcement action charged duct cleaning operators with failing to register.
  • HVAC or mechanical contractor licensing, once the work opens up the system. Florida’s statute is explicit that duct cleaning falls inside licensed contractor categories where it “requires at least a partial disassembling of the system.” Surface cleaning through the registers is a different case, so the useful follow-up is what will actually be opened or disassembled.
  • Mold licensing, if mold work is proposed. Florida and Texas license mold assessment and remediation separately, and Texas’s definition of remediation includes cleaning and sanitizing.

What we can and cannot tell you here

Eight states are not fifty, we did not look at city or county rules at all, and thresholds, permit triggers and grandfathered categories vary. Nothing here is legal advice and nothing here tells you whether your contractor needs a license. Check current requirements with your own state licensing board, contractor registration office, or consumer protection division and confirm the company appears in that record under its exact legal name. In a 2025 North Dakota news account, neither the North Dakota nor Minnesota Secretary of State or Attorney General offices could identify a duct cleaning business as licensed Single source — a check the homeowner could have run for free beforehand.

Treat a company’s own claim that your state licenses duct cleaners as something to verify. Claims of that kind that we traced led back to duct cleaning companies’ marketing pages rather than to any state agency.

Question 9 is the one people forget

Almost every documented escalation in the record happened at the moment of an unexpected finding. The finding may well be real; duct systems do contain surprises. What protects you is the process agreed in advance: stop, show, quote in writing, wait for approval. If a finding involves mold, remember that visual inspection alone cannot confirm it — the EPA notes expert or laboratory analysis may be needed, and puts laboratory confirmation at around $50. Mold work can also carry a licensing requirement that duct cleaning does not: Florida and Texas license mold assessment and mold remediation separately, both with exemptions, and Florida bars an assessor from remediating a structure they assessed within the previous 12 months and bans referral payments between the two roles. Asking who is licensed to make the finding, and whether the same firm may sell the cure, is a fair question rather than an accusation. And if wet or moldy fiberglass insulation is found, the EPA’s position is that it cannot be effectively cleaned and should be removed and replaced, so a chemical treatment sold as an alternative is being sold against the guidance. See how to test a mold finding before you authorize anything.

Inspection is not an add-on to the cleaning

“Duct cleaning and inspection” is searched as though inspection were a companion service bought alongside the cleaning, the way a filter change gets bundled in. That has the order backwards. The EPA’s answer to how a homeowner knows whether they need duct cleaning is a visual inspection of the system, and its finding is that if the inspection shows no large deposits of dust or mold, cleaning is probably unnecessary Verified fact. Inspection is not added to the cleaning. It is the step that decides whether there is a cleaning to buy, and a contractor who will not look before quoting has inverted the sequence Editorial assessment.

What a real inspection involves

  • Looking inside the runs, not at the covers. Registers and grilles come off, and someone looks into the supply and return openings with a light or a camera, at locations you can find again afterward.
  • Opening the air handler. The blower, the evaporator coil and the drain pan live inside a cabinet. If the cabinet stays shut, the components where moisture and debris actually collect together were not inspected.
  • Identifying the duct material. Bare sheet metal, fiberglass duct board, fiberglass-lined metal and flexible duct are cleaned by different means, and in some conditions the fibrous ones are replaced rather than cleaned. The material governs both the method and the price.
  • Checking for asbestos-containing materials before anything is cut or pulled. The EPA instructs that the system be inspected for them before cleaning, and names register boots specifically. No source we have gives an age cutoff, so it is a fair question whatever year the house went up, and material in good condition is best left undisturbed.
  • Looking for moisture, not only dust. The EPA treats substantial standing water or debris in the condensate pan as a problem requiring immediate attention, and identifies condensation on cooling coils as a major factor in moisture contamination.

What you should be shown

Not a photograph. A location in your own house, opened in front of you, that you can return to at the end of the job and look at again. What a before-and-after pair does and does not prove covers the difference between that and an image you cannot place. Ask for the findings in terms you can check: which runs, how much, and what material.

One limit applies to every inspection, however careful: it cannot confirm mold. The EPA is explicit that visual inspection alone cannot establish that a growth is mold and that expert or laboratory analysis may be needed, putting laboratory confirmation of a sample at around $50 Verified fact. NADCA, the industry’s own trade association, names being told without proper inspection that mold or another dangerous substance is present as a common red flag. Those two facts belong together: the finding that most often justifies an expensive quote is the one a look inside the duct cannot deliver.

The incentive problem, stated plainly

An inspection performed by the company that profits from the cleaning carries an obvious conflict. The person deciding whether you need the work is the person selling it, and we will not present a contractor’s inspection as neutral evidence.

The conclusion usually drawn from that is the wrong one, though. The answer is not to skip the inspection and buy the cleaning on faith, which is the outcome the incentive would prefer anyway. It is to see the evidence yourself, at a location you can identify, before agreeing to anything, and to treat “there is nothing here” as a good result rather than a wasted visit. The three conditions that justify the work are the standard to hold any finding against.

Three questions not to bother asking

  • “Will this improve my family’s health?” No honest answer to this question will be useful, and a confident yes is a reason to hang up. The EPA states that duct cleaning has never been shown to actually prevent health problems, and that assessment covers the entire service category including certified, competent companies. Duct cleaning is building maintenance, not a medical intervention.
  • “How often should I have this done?” The framing is wrong, so the answer will be too. The EPA does not recommend routine cleaning, only cleaning as needed based on inspection. A company that recommends a fixed interval is describing a business model. See how often ducts should be cleaned.
  • “Are you NADCA certified?” Ask it, but do not stop there — the answer is unverifiable in the moment and NADCA warns that some companies falsely claim membership. Ask for the exact legal name and check the directory yourself. What the credential does and does not guarantee is covered separately.

What you should have in hand before you agree

A one-line duct cleaning quote compared with an itemized oneA vague quote gives a single price with no scope, such as whole house duct cleaning for a low advertised figure. An itemized quote states the number of supply and return openings, names the components included such as the air handler, blower and coil, states whether access openings will be cut and resealed, gives the total time and crew, names any chemical product proposed, and confirms the price is final. The difference matters because state enforcement records document advertised prices that covered only part of the system.What you usually get“Whole house duct cleaning”$89✗ How many vents? Not stated✗ Which components? Not stated✗ Access openings? Not stated✗ How long, how many crew? Not stated✗ Any chemicals? Not stated✗ Is this the final price? Not statedWhat to insist on instead✓ 12 supply openings, 2 returns✓ Air handler, blower, coil included✓ Access cut and resealed to standard✓ Estimated hours and crew size✓ No chemical unless agreed in writing✓ Price is final unless scope changes✓ Inspection of the same spot, before and afterThis is not a style preference. It is the difference the enforcement record turns on.Washington State documented ads omitting that only half the heating and cooling system was included.
The itemized column is not a wish list. Every line on it corresponds to something that state attorneys general found missing from the advertising in real enforcement cases.
  1. The full legal business name, address, and the registration or license the company says applies to this work in your state, with the number.
  2. A written count of supply registers, return grilles, and separate heating and cooling systems.
  3. A component list marking each element in or out, including access openings.
  4. A total price for that scope, plus any per-vent overage rate stated in advance.
  5. The method and equipment named.
  6. Any chemical product named, with its EPA registration number and approved use surfaces.
  7. A certificate of insurance you can verify with the carrier.
  8. The change-order process in writing.
  9. Cancellation terms, if you have already signed anything.

If a company supplies all nine, the remaining risk is workmanship, which is a category with ordinary remedies. If a company will supply none of them, you have learned what you needed to for the cost of a phone call.

How many quotes should I get?

At least two, and ask all of them the same questions. The comparison is more informative than any single answer, because it surfaces scope differences that a single quote hides.

Can I ask these questions if the company called me?

You can, but weigh the source. Unsolicited sales calls dominate the enforcement record: one Washington case documented more than 13 million robocalls, with caller ID spoofing across more than 100 numbers using local-sounding names. A company you found and contacted yourself starts from a materially different position.

What if they answer everything well and the price is still much higher than the ad?

Then the ad was the problem, not the quote, and you now have a real number to compare against other real numbers. That is a normal outcome and not a scam — it is category (c) advertising, which the Better Business Bureau found in about a third of the companies it studied in one metro area.

Is there anything here I could just do myself instead?

Part of it, and the part is larger than the trade usually admits. Washing registers and grilles, vacuuming the accessible boots, fitting the filter properly, and looking inside with a light are all ordinary homeowner maintenance, and doing them first often answers the question a quote was going to charge you to answer. Past the register face the job needs equipment you do not own. We draw that line precisely, including the safety limits on an older house.

Should I be present during the work?

If you can be, yes — not to supervise the technique but to see the system opened and to be available for a change-order conversation rather than being telephoned for a decision. Being present also makes questions 6 and 9 enforceable rather than theoretical.

What to do next

Sources & references