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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 insurance and credentials can I verify? The full legal entity name, physical address, any state registration or license number, and a certificate of insurance you can confirm with the carrier. 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. 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 involved unregistered 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 Typical range, 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 cost calculator converts a vent count into a range you can hold a quote against, and the cost guide explains why published figures 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. Colorado’s case put a number on the shortcut — two to three hours advertised against five to eight hours actually required.

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.

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.

Licensing varies and we cannot look it up for you

Requirements for contractor licensing, registration, and bonding differ by state and sometimes by city or county, and there is no dependable national list. 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.

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. 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 mold in air ducts.

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

  1. The full legal business name, address, and any license or registration 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.

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