Choose a duct cleaner the way you would choose any contractor for invisible work: verify NADCA membership and ASCS certification, ask method questions about negative air and agitation, require a written scope, confirm insurance, and read reviews for patterns rather than star counts. Any company that resists verification has answered your question.
📞 Call (866) 370-5390“Verify NADCA membership in the association's own directory, not by the logo on a company's website.”
“Three method questions, on negative pressure, agitation, and system coverage, eliminate most coupon crews in one phone call.”
“No written scope before dispatch means the price will be written in your kitchen instead.”
“Read the worst reviews first; how a company handles criticism predicts how it will handle your complaint.”
Most home services leave visible results: a roof, a floor, a painted wall. Duct cleaning leaves results you cannot see without tools, performed inside cavities you rarely open, by an industry with almost no licensing barrier in most states. That combination means the usual quality signals, such as looking at the finished work, barely function. Your protection comes almost entirely from screening before the truck arrives. The encouraging part is that good screening is fast and discriminating: a handful of verification steps and method questions will eliminate the coupon crews within minutes, because their business model depends on customers who do not ask. This checklist is ordered by power-to-effort ratio. Certification lookup takes two minutes online. Method questions take one phone call. A written scope costs an email. If a company survives all of it, you have found the minority of the market worth hiring.
NADCA, the National Air Duct Cleaners Association, is the industry's main standards body, and membership requires companies to have at least one certified Air Systems Cleaning Specialist, an ASCS, on staff and to agree to follow the ACR standard for assessment, cleaning, and restoration. Verification is not a matter of trusting a logo on a website, since logos are freely copied. Use NADCA's own online directory to search the company by name and location, and confirm the listing matches the legal business name you were given. Ask which technician on your job holds the ASCS credential; on a well-run crew, the answer is immediate. Membership is not a guarantee of honesty, and plenty of decent independent operators are not members, but it is a strong signal: it shows investment in training, a standard the work can be measured against, and an organization that can hear a complaint.
Three questions on the phone will sort most of the market. First: do you put the system under negative pressure, and with what equipment? The right answer describes a truck-mounted or portable HEPA-filtered vacuum collection device connected to the trunk line, so dislodged debris is pulled out of the house rather than scattered into it. Second: how do you agitate the duct surfaces? The right answer names mechanical tools, such as rotating brushes, air whips, or compressed-air devices, working toward the vacuum. Third: what parts of the system are included? The right answer covers supply and return runs, trunks, and air handler components, not just the few feet visible behind each register. A company that answers with brand names, tool specifics, and process order does this work daily. A company that answers with we deep clean all the vents is describing a shop vacuum and a coupon.
The best companies treat verification as part of the service rather than a favor. Ask what evidence you will receive that the cleaning happened and worked. Strong answers include before-and-after photographs taken inside your ducts at marked locations, borescope or camera-rod video you can watch live, and a walkthrough at completion with the registers off. NADCA's standard describes verification methods up to surface testing, though photography is the practical norm for residential work. The critical detail is provenance: images should be taken in your presence, inside ducts you can identify, not delivered from a phone gallery. A company that offers verification unprompted is aligning its incentives with yours, because it expects the after photos to be worth showing. A company that bristles at the request, or says you will be able to feel the difference, is asking you to buy invisible work on faith.
Before anyone is dispatched, you should hold a document that answers five questions. What is included: the count of supply registers, return grilles, trunk lines, and systems, plus whether the blower compartment, coil, and plenums are covered. What method will be used: negative pressure source removal, with the equipment class named. What is excluded: dryer vents, sanitizing treatments, and repairs are commonly separate, and the document should say so. What the total will be, stated as a complete figure for the defined scope, with any conditions that could change it spelled out in advance. And what verification you receive at completion. The scope is your anchor against the on-arrival escalation described in our scam field guide: when a crew discovers a reason mid-job to expand the work, the conversation returns to the document. Legitimate companies produce this paperwork routinely. Its absence is itself a finding.
Duct cleaning crews work in attics and crawl spaces, open your air handler, and occasionally drill access holes in trunk lines. Things can go wrong, and when they do, the difference between a nuisance and a disaster is the company's general liability insurance. Ask for a certificate of insurance naming the carrier, and note that legitimate companies field this request constantly and can have their agent send it the same day. Workers' compensation coverage matters too; without it, an injury on your property can become your homeowner policy's problem. Licensing varies by state, since some states regulate duct cleaning under HVAC or contracting licenses and others barely regulate it at all, so check your state contractor board's website for whatever registration applies and confirm the legal business name matches. A company that hesitates on insurance is telling you how it plans to behave when something breaks.
Star averages are the least informative part of a review profile; patterns are the most. Real review histories accumulate unevenly over years, mention specific technicians, neighborhoods, and job details, and include middling reviews with mundane complaints like scheduling delays. Purchased or farmed profiles cluster: dozens of five-star reviews in a few weeks, generic phrasing that could describe any service, reviewer accounts with no other activity, and photogenic praise that never names a detail an actual customer would know. Check multiple platforms, because a company that is glowing on one and absent everywhere else earned its glow with a credit card. Read the worst reviews first and watch how the company responds; a defensive or absent response pattern under criticism predicts how your complaint will be handled. And treat review count claims on the company's own site as decoration until you find them on a platform the company does not control.
Some signals justify hanging up rather than probing further. A whole-house offer priced below any plausible labor cost is the front end of a bait-and-switch, as our scam field guide details. Refusal to provide a written scope, or insistence that pricing can only be determined on site, converts your kitchen into a negotiation room. Vagueness on equipment, an inability to say the words negative pressure, or hostility toward method questions reveals a crew without the machinery the job requires. Phone pressure tactics, such as today-only pricing or a truck already in your area, are manufactured urgency. No verifiable address, a business name that does not appear in your state's registry, or a review profile born last month all suggest an operation built to be abandoned. None of these requires you to be certain. Screening is not a courtroom; a credible doubt is reason enough to keep looking.
A referral can compress your search, but it should never replace your screening. DuctDove is a referral service: we connect homeowners with local, independent duct and dryer vent technicians, we never perform the work ourselves, we do not fake reviews, and we do not sell rankings. That is exactly why we publish this checklist and encourage you to run it on anyone we send, because a referral that asks to be exempt from verification is not a referral, it is an ad. Use the referral to skip the coldest part of the search, then apply everything above: confirm the NADCA listing yourself, ask the method questions yourself, and get the scope in writing addressed to you. Two companies passing the same checklist can then compete on scope and schedule, which is the boring, productive competition this industry needs more of. The checklist is the point. The referral is a shortcut to candidates worth checking.
No. Skilled independent operators exist outside the association. But membership provides three things that are hard to verify otherwise: a certified ASCS technician, a published standard the work must follow, and a body that can hear complaints. If a non-member impresses you, apply the method and scope questions with extra rigor.
Ask them to describe their negative pressure setup. Companies doing standard source-removal work answer instantly with equipment specifics because it is the center of their process. Companies without the equipment deflect into vague language about deep cleaning and powerful vacuums. One question, asked early, saves the rest of the call.
Yes, ideally two or three written scopes from companies that passed your screening. The value is less in comparing totals than in comparing scopes: differences in what each company includes reveal who intends to do complete work. A scope that is vaguer than its competitors is a negotiation waiting to happen.
Reputable companies often book out days to weeks, especially around seasonal changeovers when demand peaks. Treat availability as a mild positive signal; the crews that can always come today are often the ones nobody books twice. If your need is not urgent, scheduling in a shoulder season is usually easier.
We connect you with local technicians and never perform or supervise the work, so we cannot honestly guarantee outcomes, and we will not pretend otherwise. What we commit to is the integrity of the referral itself: no faked reviews, no paid rankings. Run this checklist on every referral, including ours.
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