Worried about mold in your air ducts? Here are some signs you shouldn’t ignore. Contact Thomas Hoffmann Heating & Air for a professional inspection today.
Mold is one of those household problems that often hides in plain sight, especially when it grows in places you can’t easily see, like inside your HVAC ductwork. Unfortunately, what you don’t see can still impact your health, air quality, and energy bills.
At Thomas Hoffmann Air Conditioning & Heating, we’ve helped countless St. Louis homeowners identify and resolve hidden mold issues inside their air systems. If you’re wondering whether there might be mold lurking in your air ducts, here’s what you need to know.
Love that it’s the same technician every time. Let’s me know what he found and any concerns he might have regarding our units. Great customer service.
Response from the owner:Thank you, Theresa! We're glad to hear you appreciate having the same technician and the communication about your units. Your feedback on our customer service means a lot to us!
From the phone to the completion of the job everyone is so polite and informative. I had Giovani as our representative and he was very informative and professional, and knew exactly what the problem was. Thanks so much.
Response from the owner:Thank you for the kind review, Frank! We appreciate you and your business.
Zach did an excellent job! Always courteous and friendly. We would highly recommend calling Thomas Hoffmann HVAC for any heating and cooling needs.
Response from the owner:Thank you, Allan! We're glad to hear that Zach provided excellent service and appreciate your recommendation for Thomas Hoffmann HVAC.
Was able to locate the problem right away and replace a switch and add Freon very nice job by this employee. I will recommend Thomas Hoffman for future references.
Response from the owner:Thank you, William! We're glad to hear that our team was able to quickly address the issue and that you had a positive experience with Thomas. Your recommendation means a lot to us!
I had Nick come out. He was awesome. Very knowledgeable, prompt and helpful. I will definitely recommend Thomas Hoffmann HVAC to others in need of HVAC support.
Response from the owner:Thank you, Jack! We're glad to hear that Nick provided you with excellent service. We appreciate your recommendation and look forward to assisting you and others in the future.
From our initial quote until the new furnace and AC were completed, everything was smooth and efficient. Zachary and Giovanni were excellent on-site, taking time to explain the installation as well as leaving the home clean. Thank you Thomas Hoffmann team
Response from the owner:Thank you! We're glad to hear that the installation process was smooth and efficient. Zachary and Giovanni will be pleased to know their efforts made a positive impact. We appreciate your kind words about the team!
Update 4/6/26: Zach Sperling is such a pleasant and knowledgeable technician that I recommend him highly. Thomas Heating has been a wonderful company to work with in my maintenance plan. If you are looking for a reputable company, look no more.
This company is so responsive that I love them. They respond immediately, and I trust them to tell me what needs to be done. I haven’t been steered wrong yet. They are genuinely nice to work with and honest. I use their maintenance program which I highly recommend.
Response from the owner:Thank you for your kind words, we truly appreciate your trust in us and are glad to hear about your positive experience with our services.
work good but got at least 6 messages from them very annoying
Response from the owner:Thank you for your feedback, Harold. We appreciate your input and understand how too many messages can be frustrating. We'll work on improving that experience for you.
Nick was great! He came right out and was able to solve the problem fairly easily. He communicated well and helped us prevent a future problem as well.
Response from the owner:Thank you for the review, Philip! We are happy to hear you had a pleasant experience working with us.
Response from the owner:Thank you, Pat, for your kind words about Giovanni; we appreciate your feedback and are glad to hear that he made a positive impression.
They have never failed to fix my hvac problems. These folks are top tier.
Response from the owner:Thank you for the wonderful feedback, Greg! We're glad to hear that you've had such positive experiences with our team. Providing timely and effective service is our priority, and we're here whenever you need us. Looking forward to assisting you again!
Giovanni was very professional, helpful, patient and helped me figure out the issue, if it was covered under warranty, and next steps. Great overall experience and much appreciated.
Response from the owner:Thank you, Amy! We're glad to hear that Giovanni provided you with such professional and helpful service. Your appreciation means a lot to us!
Always professional and thorough whenever they service our home. We have used Thomas Hoffmann Air Conditioning & Heating multiple times since we moved into our home and will continue to use them in the future.
Response from the owner:Thank you for the thoughtful review, Joe. We appreciate you and your business!
0 stars if I could. Bought a faulty (not to mention overpriced) surface igniter, called back five minutes later after installing, of course they didn’t stand behind their part. Go to Grainger instead. Same (working) part, half the price.
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My furnace was not working. A very nice gentleman came out this morning and fixed the problem and now I have much needed heat. He was very professional and courteous. I will definitely be using them again when the need arises.
Response from the owner:Thank you for the positive feedback! We're glad to hear that you were pleased with our prompt and friendly service. We look forward to assisting you again in the future!
I will always call Hoffmans for my air and heat needs. They were out to my daughters house that day and fixed it. It was right before the weekend storm with below zero temps the next day. They saved my daughter and grandbabies. I could never thank them more.
Response from the owner:We are so happy to hear that we could help! Thank you for the kind review.
Snow and drifting snow covered intake and out take vents causing the furnace emergency to shut off furnace. Cleaned off the driftibg/ snow off roof and vents furnace works perfect now. Thank you and great job Nick.
Response from the owner:Thanks for the great review, Scott! We appreciate your support.
5 stars! Nick was here to fix my heater within 2 hours of my call. He explained the problem to me thoroughly and got the job done quickly & professionally. Thank you so much!
Response from the owner:Thank you for the kind review, Jennifer! Glad we could help.
Extremely thorough and educational. They do a wonderful job of explaining everything and making sure I was comfortable knowing how the systems worked in my house!
Response from the owner:Thanks for the great review, Matthew! We appreciate your support.
I noticed a strange noise that I was concerned was linked to my furnace. I called Thomas Hoffman Heating & Cooling and Nick came right out. He was very thorough checking all components. Thankfully all checked out for us this visit. Definitely recommend Thomas Hoffman Heating & Cooling!
Response from the owner:Thank you so much for the kind review, Abby! We appreciate your business and look forward to servicing you in the future.
Thomas Hoffman is a wonderful company to work with. Techs are knowledgeable, personable & efficient.
Response from the owner:Thank you, Christine, for your kind words about our team; we appreciate your feedback and are glad to hear you had a positive experience!
Got a quote over the phone. Everything was explained thoroughly. Dakota, my technician arrived and on time, was very professional and knowledgeable. He didn’t try to upsell or change anything. He did a great job. We can already tell the difference since the ducts and vents were cleaned. Would recommend an use Hoffman again in the future.
Response from the owner:Happy to hear you had a pleasant experience using Thomas Hoffmann!
The technician, Ryan, was knowledgeable and helpful in identifying the issue with our mini split AC unit. They are the second company we called after issues with the first and will be using Hoffmann again.
Response from the owner:We are so happy to hear your experience with Thomas Hoffmann was pleasant. Thank you for your kind review, & we look forward to working with you in the future!
⚠️ Why Mold in Air Ducts Is a Big Deal
Your ductwork is the circulatory system of your home — if there’s mold inside it, spores can be pushed into every room whenever your HVAC system runs.
That can lead to:
Aggravated allergies and respiratory issues
Musty odors throughout your home
Decreased air quality
Long-term health risks, especially for children and the elderly
And because mold thrives in damp, dark environments, your ducts are the perfect hiding spot.
🔍 Signs You May Have Mold in Your Ductwork
While you might not see the mold directly, your HVAC system may be sending clear warning signs:
1. Musty or Earthy Odors When the AC or Heat Runs
If your home smells like an old basement every time the air turns on, mold or mildew in the ducts may be the culprit. This smell often worsens during humid summers in St. Louis. 🌧️
2. Allergy or Asthma Flare-Ups Indoors
Have you or your family noticed itchy eyes, sneezing, or shortness of breath indoors, especially when the HVAC is on? Mold spores circulating through your air supply can be a hidden trigger.
3. Visible Mold Around Vents or Registers
Sometimes, mold can start to appear around supply vents or on the ceiling nearby. This could be a sign it’s also growing inside the duct system.
4. Inconsistent Airflow or Unusual Humidity
Duct obstructions and moisture buildup from mold can interfere with airflow. If certain rooms feel more humid or aren’t cooling properly, mold might be part of the issue.
5. Recent Water Damage or Flooding
If your home recently experienced a leak, plumbing issue, or flooding — especially in the attic or basement — your ducts may have been exposed to moisture, creating the ideal breeding ground for mold.
🧪 How to Confirm Mold Growth
Because mold is often hidden deep within your ductwork, the only way to know for sure is to have a licensed HVAC technician or indoor air quality specialist perform a thorough inspection.
At Thomas Hoffmann Heating & Air, we use advanced tools and techniques to:
Inspect deep within your ductwork
Test air quality for contaminants
Identify moisture sources
Recommend cleaning or remediation solutions tailored to your system
🧼 Can Mold in Ducts Be Removed?
Yes — but it requires the right equipment and expertise.
Duct cleaning alone is not always enough. If mold is actively growing, it may require professional treatment, and the source of the moisture must be addressed to prevent its return.
We often recommend:
Sealing duct leaks
Installing a whole-home dehumidifier
Upgrading air filtration or UV purification systems
🛡️ How to Prevent Mold in Your HVAC System
After remediation, prevention is key. Here’s how you can reduce the risk of mold coming back:
Replace HVAC filters regularly
Schedule seasonal maintenance and duct inspections
Install a dehumidifier (especially in basements or crawlspaces)
Ensure proper drainage from your AC unit
Keep air vents open and unobstructed
🏡 Why St. Louis Homes Are Especially Vulnerable
The humid Midwest climate, combined with older home construction and basements, makes many homes in St. Louis naturally prone to moisture issues.
That’s why our team at Thomas Hoffmann specializes in whole-home air quality solutions designed specifically for our region, not just generic fixes.
📞 Concerned About Mold in Your Air Ducts? Call the Local Experts.
Don’t ignore the signs. Mold in your ducts can worsen over time, impacting both your comfort and health. Let our experienced team provide the answers and solutions you need, with the honest, local service you expect.
