The short answer
Two answers separate a real duct cleaning company from a vent vacuuming service: how many openings they counted, and whether the quote names the trunk line, the plenums, the blower and the coil. A company that will not put those in writing is quoting a different job from the one you think you are buying.
I dispatch for SafeAir, so I hear what other companies told people before they called us. The six questions below are the ones that decide which company you choose, and residential air duct cleaning is what a complete job should cover.
The six questions, and the answers that pass
Ask them in order. A passing answer is specific; a failing one is a reassurance.
- How many supply and return openings will you clean, and how do you count them?
Passes: they count on site, the way our technicians count every opening before a price exists, or they ask how many rooms and vents you have. Fails: a flat price with no count, which usually means a set number of vents and the rest extra. - Does the price include the trunk line and both plenums?
Passes: yes, and they name them. Fails: “the whole system”, with no part named. The trunk carries every room’s air; skipping it leaves the reservoir in place. - Will you clean the blower and evaporator coil inside the air handler, and the drain pan under them, and is any of that extra?
Passes: a clear yes, or a clear price per item. Fails: silence, because blower cleaning and furnace cleaning are where the growth usually sits. - How do you get inside the duct, and how do you close it?
Passes: they name the panels they will cut, and say how each one is closed and sealed behind them. Fails: “in through the vents”. A hose fed through a register reaches about 7 feet and will not reach the trunk line at all. - What equipment, and is the system under negative pressure the whole time?
Passes: named machines and a figure. Fails: “commercial grade equipment”, which names nothing. Ours are HyperVac units running both MERV 15 and HEPA filtration, holding the system under negative pressure for the whole evacuation, listed on the equipment page. - Who exactly holds the certification here, the company or the individual technician?
Passes: they distinguish the two without being pushed. Fails: any claim that the company itself is certified by NADCA, which is not a thing a company can be.
Six answers take about 4 minutes on the phone. Then the limit of them: you cannot see inside your own trunk line, and no question fixes that. What the answers do tell you is whether the company intends to clean it, which is the thing you are actually buying.
Check the credential yourself, in under a minute
NADCA is the trade association for this work. Membership belongs to a company; the ASCS credential, which stands for Air Systems Cleaning Specialist, belongs to a person who has passed an exam. That difference is where most of the fudging happens.
Search any Missouri company in the NADCA directory. The listing shows designations by person: ASCS for a cleaning specialist, CVI for a ventilation inspector. Ours is there. The entry shows two separate things: SafeAir listed as a member company since February 2020, and Dustin Morter holding ASCS in his own name. I am not NADCA certified myself, and no page of ours says otherwise.
Two more checks worth the minute: the BBB file, which shows our accreditation from 2012, and whether the insurance covers work inside an HVAC system rather than general cleaning.
The two-line test for a vent-only clean
A vent-only service vacuums the first few feet behind each register and leaves. It is the outcome question two is written to catch. It is not fraud, just a different product at a price that makes sense once you know that.
Ask for the quote in writing and look for two lines:
- A count of openings, not a flat “whole house”. A number means somebody looked.
- The named parts: the trunk line and the branch runs off it, both plenums, every register and return grille, the blower and the coil, and how access is made and closed.
Ask too whether the dampers get opened: a closed damper hides a whole branch run from the vacuum. A dryer vent is a separate line and a separate price. With both lines you are buying the job the EPA describes: the whole system, not the ends of it. Without them, you are paying whole-system prices for vent vacuuming. The process page is written down for exactly this reason.
Is duct cleaning a scam?
The advertised $79 whole-house special is the scam. The price buys a vacuum at each register. The upsell arrives once the technician is in the house: duct sanitizing, mold remediation, a per-vent charge for what you thought you had bought.
The service itself is not a scam. The EPA does not recommend it on a schedule, and it names three conditions where the work is warranted: visible mold, vermin, or debris being released into rooms. A written quote and a look at the signs are what separate a real job from a hook.
What a loaded duct actually looks like
Every company shows a photograph. Here is ours, with the job it came from. The Gartland home in Kirkwood is 1,502 square feet with six openings, cleaned on May 30, 2024. We found dirt, dust, pet hair, skin cells and construction debris. In the trunk run it was not a film but a covering, over the ceiling, the walls and the floor, thick enough to hide the metal.
A photograph proves somebody opened your duct. It does not prove the price was right or the whole system was done. Six openings on 1,502 square feet is one of the smallest systems we have documented, so a load like that has little to do with the size of the house. Across the 13 homes we have photographed and written up, the list barely changes: carpet fibers, pet dander, drywall dust after a remodel, rust, and every so often an insect. Other jobs look different again. A 3,683 square foot house in Arnold still held debris from when it was built. An O’Fallon home of 1,900 square feet with 17 openings was booked as routine maintenance, and it still held dirt, pet hair and construction debris that none of its vent covers showed.
When you should not book at all
Four cases where I would tell you to keep your money. Two come up weekly.
- Nothing is wrong and nobody has looked. No smell, no dust, a current filter: you probably do not need us this year.
- The filter is months overdue. Change the filter, wait two weeks, and see whether the dust comes back.
- The complaint is airflow in one room. That is a damper, a crushed flex run or equipment, so you need an HVAC contractor and not a cleaner.
- The house is damp. Fix the water first, or mold remediation and duct sanitizing both become repeat purchases.
Questions people ask next
Getting a straight answer for your own home
Run the six questions past whoever you are considering, ourselves included, and keep the one that answers in specifics.
Ours runs in that order: a look inside first, then the scope in writing, then a number that does not move on the day. Decide against it and there is a $25 travel fee, which comes off the moment you book. Call 314-900-3828, or ask for a visit on the estimate page. The cost page shows how the number is built. We have worked out of Imperial since 2002, across Jefferson County and St. Louis County. Where the problem is growth rather than dust, air duct mold cleaning is the service you want quoted.
