Twelve questions, asked before booking, will sort honest duct cleaners from coupon crews: certification, experience, negative-air equipment, agitation method, inspection practice, written scope, what the quote includes, what could change it, photo proof, verification, insurance, and breakage policy. For each, there is a good answer and a disqualifying one.
📞 Call (866) 370-5390“Your leverage is highest before booking; ten minutes of questions outweigh an hour of on-site negotiation.”
“The fastest filter is equipment fluency: crews doing real source removal can describe negative pressure and agitation in concrete detail.”
“A good company can name what could change the total in advance; it depends what we find is a scam's blank check.”
“Hostility toward pre-sale questions predicts hostility toward post-sale accountability.”
Duct cleaning is invisible work, so your leverage lives almost entirely before the appointment. Once a crew is in your hallway, the psychology tilts toward them: the equipment is unloaded, your afternoon is committed, and declining feels expensive. A ten-minute phone interview reverses that tilt. The twelve questions below are ordered the way a booking call naturally flows, and each comes with the shape of a good answer and the shape of a bad one, because in this industry the phrasing of an answer is often more diagnostic than its content. Companies doing standard work answer these questions all day and enjoy them; they are a chance to show competence. Companies running the bait-and-switch pattern described in our scam field guide are structurally unable to answer several of them, and will try to move you to just letting the technician take a look. Take notes. The notes become your written record.
Question one: are you a NADCA member, and will an ASCS-certified technician be on my job? Good answer: yes, here is our listing in the NADCA directory, and the certified tech's name is given without hesitation. Bad answer: we're certified, with no ability to say by whom, or a claim you cannot find in NADCA's own directory; certification by an organization you have never heard of and cannot look up counts as no. Question two: how long has this company operated under this exact name? Good answer: a specific number of years that matches the state business registry and the age of the review profile. Bad answer: vagueness, a recent name change explained defensively, or a long-experience claim attached to a business registered months ago. Neither question guarantees quality by itself, but together they establish whether the entity you are hiring is built to still exist when you have a complaint.
Question three: do you clean under negative pressure, and what does the setup look like? Good answer: a truck-mounted or portable HEPA-filtered vacuum collection unit connects to the trunk line and keeps the whole system under suction while we work, so debris leaves the house instead of entering it. Bad answer: we use a powerful vacuum on each vent, which describes cleaning a few visible feet while pushing the rest deeper. Question four: how do you dislodge debris from the duct walls? Good answer: named agitation tools, such as rotating brushes, air whips, or compressed-air skipper balls, worked toward the vacuum connection. Bad answer: the suction takes care of it, because it does not; settled debris needs mechanical agitation, which is why NADCA's standard pairs agitation with collection. These two questions are the fastest filter on this list. A crew without the equipment cannot fake fluency about it.
Question five: do you inspect before quoting, and what does the inspection include? Good answer: yes, we look at the system first, by camera or in person, count registers and returns, check the air handler, and tell you honestly if cleaning is not warranted. That last clause matters; the EPA recommends cleaning on evidence, and a company willing to find no evidence is a company you can trust with a yes. Bad answer: no inspection needed, every house is the same, or an inspection that is free but mysteriously always finds urgent problems. Question six: will I receive a written scope before the appointment? Good answer: yes, listing systems, register and return counts, air handler components, method, exclusions, and total. Bad answer: we'll work all that out on site, which relocates the negotiation to your kitchen, with the crew's schedule as the pressure and your afternoon as the hostage.
Question seven: what exactly does the quoted figure include, start to finish? Good answer: a complete recitation, including supply and return runs, trunk lines, register removal and cleaning, blower compartment, and cleanup, with anything excluded named explicitly, such as the dryer vent or sanitizing treatments. Bad answer: a low headline figure that covers a base service the company itself describes as insufficient, which is the coupon structure our scam field guide dissects. Question eight: what circumstances could change the total once you are on site? Good answer: a short, concrete list, such as discovering an additional air handler or inaccessible ductwork, with the promise that any change is presented and approved in writing before work continues. Bad answer: it depends what we find, unbounded. You are not asking these to negotiate. You are asking to see whether the number is an honest estimate or a door prop.
Question nine: will you take before-and-after photos or video inside my ducts, in my presence? Good answer: yes, routinely, at marked locations you can identify as your own home, often with a borescope you can watch live. Bad answer: reliance on a gallery of dramatic photos that could be from anywhere, a habit our scam field guide flags because pre-loaded photos from other houses are a standard prop. Question ten: how do you verify the cleaning worked before you leave? Good answer: a final walkthrough with registers open, after-images compared against the before set, and a check that the air handler compartment is clean and reassembled. Bad answer: you'll notice the difference, which is an appeal to imagination, not evidence. Verification is the honest company's favorite subject, because it is where their work becomes visible. Discomfort with this pair of questions is one of the most reliable disqualifiers on the list.
Question eleven: are you insured, and can you send a certificate of insurance before the appointment? Good answer: yes, general liability and workers' compensation, certificate available from our agent today. Bad answer: any hedge, because crews work in attics, open equipment, and occasionally cut access holes, and an uninsured mistake becomes your problem. Question twelve: if something is damaged or the system misbehaves after the visit, what happens? Good answer: a specific process, such as report it, we return to inspect, insurance covers verified damage, and a named person answers the phone. Bad answer: that never happens. Every real service company has a breakage story and a process it produced; only companies planning to be unreachable have neither. This pair of questions is less about predicting disaster than about observing how the company talks when the subject is its own accountability. Fluency here is earned only one way.
Some answers end the call regardless of everything else. A headline offer the company itself undermines within a minute, explaining the advertised service will not really help your home, is the bait-and-switch announcing itself. Refusal to put scope in writing. Inability to describe negative pressure equipment in concrete terms. A certification claim that fails a two-minute directory lookup. Pressure phrasing, such as a truck in your area today or pricing that expires when the call ends. Hostility, even mild, toward the questions themselves, because a company that resents scrutiny before the sale will resent accountability after it. Notice that none of these judgments requires expertise; each is a company failing to describe its own ordinary operations. If a candidate passes all twelve questions, our vetting checklist post covers the remaining diligence, including reviews and state registration. And if you would like candidates worth interviewing, DuctDove exists to make that introduction; we refer local technicians, never perform the work, and expect every referral to survive this exact list.
The set is designed for a natural ten-minute call, but if you must triage, ask about negative pressure, the written scope, and what could change the total on site. Those three eliminate most bad actors. The remainder distinguish between adequate companies and genuinely good ones.
Treat it as disqualifying. The written scope is the single document that protects you from on-arrival escalation, and producing one costs a legitimate company nothing but an email. A refusal means the company wants the flexibility to define the job in your house, which is the scam's core mechanism.
Both have value. Phone reveals fluency, since practiced competence is audible, while email creates a record. A reasonable pattern is to screen by phone, then ask the company to confirm scope, inclusions, and insurance in writing. Any answer that changes between the call and the email is itself information.
No, and good companies genuinely prefer informed customers, because these questions showcase exactly the equipment and process they invested in. The interview feels adversarial only to companies whose business model depends on you not asking. Calm, specific questions are the opposite of distrust; they are how trust gets built.
We connect homeowners with local technicians and never perform the work ourselves, and we built this list to reflect what separates good operators from coupon crews. But no referral, ours included, replaces your own screening. Ask the questions yourself; the answers belong in your records, not just ours.
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