Why Mold Remediation Fails: The Role of Uninspected Ductwork

Based on insights from Christopher Thome, CVI, ASCS, VSMR, author of “HVAC Systems, Mold and the Indoor Environment”

When mold remediation doesn’t work, it’s not always because of poor cleaning. It’s often because of what wasn’t cleaned at all, and in many cases, that’s the HVAC system.

When mold remediation doesn’t work, it’s not always because of poor cleaning. It’s often because of what wasn’t cleaned at all, and in many cases, that’s the HVAC system.

Despite the best intentions, mold remediation frequently fails due to uninspected and untreated ductwork. The result? Lingering odors, returning health symptoms, and failed clearance tests.

Here’s why uninspected ductwork is one of the biggest blind spots in mold remediation today.

The HVAC System: A Hidden Reservoir of Mold

Your HVAC system circulates air throughout the building, but it also circulates:

• Mold spores

• Dust

• Pollen

• Other pollutants

Even if you remove all mold from surfaces and contents in the building, an untreated HVAC system can act like a giant mold sprinkler, spreading contamination back into the environment after remediation.

❌ The Common Mistake: Skipping HVAC Inspection

In HVAC Systems, Mold and the Indoor Environment, Christopher Thome explains that many remediation companies don’t inspect the HVAC system unless the client insists on it. Why?

• Lack of proper training or licensing

• Not addressing the mechanical operation of the air conditioning system to ensure it is properly maintaining the temperature and humidity within the environment

• The assumption that duct cleaning is “enough”

  
  

But Thome warns that duct cleaning alone does not equal HVAC mold remediation. Ducts, coils, plenums, and blower assemblies often contain hidden contamination that can’t be removed without mechanical access, surface disinfection, and sometimes component replacement.

What Remediation Should Include but Often Doesn’t

A proper mold remediation involving HVAC should include:

1.   An HVAC inspection performed by a State Licensed AC Contractor and NADCA Certified Ventilation Inspector (CVI) and Ventilation Systems Mold Remediator (VSMR)

2.  A scope of work detailing the project protocols and engineering controls

3.  Removal of biological buildup from coils and internal insulation

4.  Disinfection of metal ductwork with EPA-registered antimicrobial agents

5.  Replacement of any flex ducts or materials that cannot be fully cleaned

6.  Third party verification that all work meets specifications of the project

When these steps are skipped or only partially performed, the mold can come back; or worse, never truly leave.

Signs Your Remediation Missed the HVAC System:

Symptoms like headaches, coughing, or sinus issues are still a problem.

• Musty odors return shortly after the project is completed

• Symptoms like headaches, coughing, or sinus issues persist

• Ducts or vents show dust buildup, moisture stains, or discoloration

• HVAC components were not photographed or included in the scope of work.

  Without mechanical remediation of the HVAC system, any mold cleanup effort is incomplete by definition.

✔️ What You Can Do:

1.    Ask for a Certified Ventilation Inspection before or during remediation.

2.    Make sure your contractor is qualified to access, clean, and treat HVAC systems; or partners with one who is.

3.     Don’t accept “duct cleaning” as a stand-in for remediation.

4.     Request before-and-after photos of all internal components: coil, plenum, blower, return, etc.

5.     If you’ve already had mold remediation and still don’t feel better, schedule a post-remediation HVAC inspection.

How EnviroAir Systems Prevents Remediation Failure

At EnviroAir Systems, we specialize in the part most remediation companies ignore: the mechanical system. Our NADCA Certified Team knows how to access, document, and fully remediate HVAC systems with mold contamination.

Whether you're planning remediation or trying to figure out why you still feel sick after one, we can help you identify what’s been missed. Call to schedule an EnviroAir Systems HVAC Inspection today, 813-644-9261.