What NADCA Certified Actually Means, and How to Check a Company

The short answer

NADCA certification means a named individual has passed an exam on the industry standard. The company carries insurance and agrees to clean to that standard. It is checkable in about thirty seconds.

It is not a licence, and Missouri does not require one to clean ducts. That is precisely why it is worth checking: it is the only independent bar in an industry with no legal one.

Ours is listed here on NADCA’s directory: SafeAir Duct Care, member since February 2020, with Dustin Morter holding the ASCS credential. Check it before you read another word of this page.

On this page

What the certification actually is

NADCA is the National Air Duct Cleaners Association. It publishes the ACR standard, which is the document the trade measures a proper clean against, and it certifies individuals who pass an exam on it.

Membership and certification are two different things, and companies blur them constantly.

  1. A member company carries general liability insurance, agrees to clean to the ACR standard, and must have at least one certified individual on staff.
  2. A certified individual is one named person who sat and passed the exam. The credential belongs to them, not to the business.

So “NADCA certified company” is loose wording. What you want to know is which person holds it, and whether the company is still a member today.

ASCS: the person, not the company

ASCS stands for Air Systems Cleaning Specialist. It is NADCA’s main credential and the one that matters for duct cleaning.

There is a second one, CVI, Certified Ventilation Inspector, which covers inspecting a system rather than cleaning it. A company may hold either, both or neither.

At SafeAir, owner Dustin Morter holds the ASCS credential, and the company has been a NADCA member since February 2020. Both facts sit on the public directory, which is the point: you should not have to take our word for either.

How to check a company in 30 seconds

This is the part worth doing before anyone opens your furnace. Four steps.

  1. Open NADCA’s Find a Professional directory.
  2. Search the company name, or your ZIP code to see everyone near you.
  3. Open the listing and read the Certified Personnel line. It names the individuals and the credential each one holds.
  4. Check the member since date. A lapsed membership will not appear at all.

Pro tip: If a company is not in the directory, that is your answer. The listing is free to verify and takes half a minute, and a logo on a website is not the same as an entry in the register.

What the standard requires

The ACR standard is long, but the parts that change what happens in your house come down to four things.

  1. The whole system, not the ducts alone. Supply and return ducts, the trunk line, both plenums, the blower wheel and housing, and the evaporator coil and drain pan. A quote covering registers only is not a system clean.
  2. Negative pressure throughout. The blower passes air across the coil, the trunk line carries it to every branch run, and settled dust, pet dander, carpet fibers and mold spores travel with it. Continuous vacuum pulls that load out of the building rather than into the room, and agitating a duct without it simply spreads what had settled.
  3. Mechanical agitation. Air whips, compressed air lines or brushes physically dislodge what has bonded to the duct wall. Suction alone does not lift it, and whatever stays put simply settles again the next time the system circulates.
  4. Access openings, properly closed. Service openings get cut where needed and then resealed with metal patches, screws and foil tape, not tape alone. A badly closed opening vents conditioned air into a crawl space for years afterwards.

Our own method against that standard, including the equipment it takes, is on the air duct cleaning equipment and process page.

A clean carried out that way takes 2 to 4 hours on most single-system homes, and what it costs depends on the duct count more than the square footage. Duct sanitizing, blower cleaning, dryer vent cleaning and mold remediation are priced separately, because each is separate work rather than part of a duct clean.

That is residential duct cleaning if you want it done.

What it does not guarantee

Being straight about the limits, because certification gets sold as more than it is.

  • It does not mean the person who turns up at your house is the certified one. Ask who is actually coming.
  • It does not set a price. A certified company can still be expensive, and a cheap quote is not automatically uncertified.
  • It does not mean your ducts need cleaning. The EPA recommends duct cleaning as needed rather than on a schedule.
  • It is not a state licence. Missouri does not license duct cleaning, which is why the voluntary bar is the only one there is.

Be clear about when nobody needs calling anyone at all. A system with no growth, no smell and a filter changed on schedule probably does not need cleaning this year, certified or otherwise, and probably not next year either. If the growth is on drywall or framing rather than inside the ductwork, you will not need us at all.

That is not the job we do; you want a mold remediation contractor. And if the fault is the equipment rather than what is inside it, you need an HVAC contractor. We do not do air conditioning repair or installation.

Four questions worth asking

  1. Which named person holds the ASCS credential, and will they be on my job?
  2. Does the quote include the blower wheel, the coil and both plenums, or only the registers?
  3. How will you create negative pressure, and where does it connect?
  4. How will you close the access openings you cut?

A company working to the standard answers all four without hesitating. One that does not will talk about price instead. The credential is only part of the decision, and how to choose an air duct cleaning company works through the rest of it.

What to do next

If you are still collecting quotes, check each company against the directory first. It costs you nothing and removes most of the field.

This is what the standard is for. A supply duct in a Ballwin home, photographed on the job before anyone touched it.

Debris and lint built up along the floor and walls of a supply duct in Ballwin MO before cleaning
Before: debris across the duct floor, lint clinging to the walls. Ballwin, MO.

That did not arrive overnight, and it does not stop where the light does. The floor carries settled dust, carpet fibers, pet dander and lint. The walls have their own coating, and air passes over all of it every time the system cycles.

Here is the same run after a clean carried out to the ACR standard, with the system held under negative pressure throughout.

The same Ballwin supply duct after cleaning, back to bare sheet metal
After: bare sheet metal, same duct, same joist overhead.

One clean run is the easy part; a shop vac manages a couple of feet at the register end. A clean done to the standard means every branch run, the trunk line, both plenums, the blower wheel and the evaporator coil got the same treatment, and the debris left the building.

A full job written up end to end: a 3,683-square-foot home in Arnold, 34 ducts, August 2024, after the owners called about dust and a smell. We found mold in the air handler with dirt, pet hair and construction debris from earlier work. That is on the Butler case study.

SafeAir Duct Care has worked across Jefferson County, St. Louis County and St. Charles County since 2002 and is BBB accredited. Owner Dustin Morter holds NADCA’s ASCS credential, and the company has been a NADCA member since February 2020, both listed on NADCA’s own directory.

If you want a quote from us, call 314-900-3828 and ask for an inspection. You get the quote in writing before any work starts. We count the supply and return ducts and open the air handler before quoting, and if the ductwork is clean we will tell you that instead.