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.
The service tech Giovanni did a fantastic job. Our gas fireplace is working like new again so we’re ready for the cold weather!
Response from the owner:Thank you, Mr, for your fantastic review! We're glad to hear Giovanni provided you with excellent service and professionalism. Your recommendation means a lot to us!
⭐️⭐️⭐️⭐️⭐️ If I could give 10 stars, I absolutely would.
Last night our furnace went out unexpectedly, and with three kids in the house, the temperature dropped fast. Giovanni went above and beyond in every way possible. Instead of charging me a late-night service fee, he simply asked, “Are you decently handy?” and offered to walk me through some troubleshooting steps to get our heat back on so my children wouldn’t have to sleep in the cold.
Not only did he guide me through the process, he even FaceTimed me and showed me exactly what to take apart, how to put it back together, and what signals to watch for. It felt like having a real technician standing right next to me the entire time. Thanks to him, our heat was restored within minutes.
In a world where true customer service is hard to come by, Giovanni is a rare find. It is a guaranteed fact that any future repairs, maintenance, and the new heater/AC system we’ll be needing this coming summer/fall will absolutely be done through him. His honesty, kindness, and expertise have earned our business for life.
Highly, highly recommend.
Response from the owner:Thank you, Jeff, for sharing your experience! We're so glad to hear Giovanni was able to help you and your family during that tough situation. Your recommendation means a lot to us, and we appreciate your trust in our services for the future!
My neighbor referred these guys to me when had water heater problem. Previous company told me I needed to replace it. Tom’s technician fixed it for less than $200. This was over 2 years ago and have been using their service ever since. They are very trustworthy.
Response from the owner:Thank you, Mary, for sharing your experience and for trusting us with your water heater issue; we're glad our technician could help and that you've continued to rely on our services!
I called this company earlier today because I was having a bunch of issues with my HVAC system. They were incredibly friendly and walked me through troubleshooting step by step over the phone. They didn’t even charge me for the call. Thanks to their honest advice, I was able to get things running smoothly again. Really grateful for their help and would definitely recommend them if you want straightforward and trustworthy service. Five stars all the way!
Response from the owner:Thank you so much for the glowing review, Hector! We appreciate your business and look forward to working with you in the future.
Nick did not set current time. — Monday Hoffmans Zach came to fix correct time. We DID NOT want a timed thermostat — we prefer to set temperatures manually
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.
Clear communication about arrival, service and costs.
Response from the owner:Thank you, Margaret, for your kind words! We appreciate your feedback on our clear communication and are glad you had a positive experience.
Response from the owner:Thank you, Hank, for your wonderful feedback; we're glad you enjoyed the fast, friendly, and professional service, and we'll be sure to keep up the great work!
I will highly recommend this business for your air and heater repair. Prompt, knowledgeable and courteous service.
Response from the owner:Thank you, Judy, for your kind words and recommendation! We're glad to hear you were pleased with our prompt and courteous service.
Thomas Hoffman was very responsive to our after hours inquiry, even walked us through some trouble shooting over the phone. We provided pictures of the unit and they were able to quickly buy, schedule and install the part to keep our family warm!
Response from the owner:Thank you, Ali! We're glad to hear that Thomas was responsive and helpful in getting everything sorted out for you and your family. Your feedback means a lot to us!
Nick came by, identified the problem quickly and had it fixed. Great service!
Response from the owner:Thank you, Ted! We're glad to hear that Nick provided you with quick and effective service. Your feedback is greatly appreciated!
Great service. Responsive. Well trained technicians. Honest friendly and thorough. I highly recommend Tom Hoffmann and his team.
Response from the owner:Thank you for your kind words! We appreciate your recommendation and are delighted to hear about your positive experience with our team.
Ryan Taylor with Thomas Hoffman did an outstanding job in servicing our unit & explaining everything to me, especially how our humidifier worked, since we were new home owners & had not had one before. Thank you!
Response from the owner:Thank you! We're glad to hear that Ryan and Thomas provided you with excellent service and helped you understand your new humidifier. We appreciate your feedback!
As always, the Hoffmann technician Zach was polite, professional, and efficient. Pricing is reasonable and even more importantly, they are dependable. I will continue to use Thomas Hoffman A/C and Heating.
Response from the owner:Thank you, Mark, for your kind words about our technician and for your continued trust in Thomas Hoffman A/C and Heating; we truly appreciate your support!
Response from the owner:Thank you, Brandon! We appreciate your kind words and are glad to hear about your positive experience with Hoffmann’s professionalism and thoroughness.
Our service technician arrived right on time and was professional, friendly, efficient and courteous. We couldn’t ask for more.
Response from the owner:Thank you for sharing your positive experience with our service technician! We appreciate your kind words and are glad to hear that you were satisfied with the service provided.
I'm a new customer and had my first appointment for furnace check.My tech was Zack and what a professional. He explained how he checked system and answered all my questions. This was a very good experience
Response from the owner:Thank you, Patricia, for your kind words! We're glad to hear that Zack provided you with a professional and informative experience during your furnace check. Your satisfaction means a lot to us!
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!
I called on December 25th at midnight and started leaving a message and Thomas Hoffman the owner called me back almost immediately. He said he would come out the next morning between 8:00 and 10:00 am snd he was promptly on time. He fixed my problem and while he was there I decided to get an estimate for a new furnace and air conditioning unit. The price was very reasonable and the installers one of them being his son were both very professional very courteous, polite, arrived on time and finished the same day. I enjoy knowing that I now have the support of Thomas Hoffman heating and air conditioning along with the peace of mind that comes with owning a Trane. Nothing stops a Trane.
Albert Koesterer
Response from the owner:Albert thanks so much for your kind reviews and your business. We truly appreciate it!!!
The Thomas Hoffmann team did a great job taking care of our semi annual HVAC maintenance. They not only worked with us to schedule the visit, but also did an excellent job sending us reminders on when they would be out.
Response from the owner:Thank you so much for the great review, Bob! We appreciate your support and are happy to hear you had a great experience!
Nick was excellent. Super profession, quick, and up front with the pricing (which was fair). Hopefully we don't need to call anyone to fix our AC again, but if we do - I'm calling Nick!
Response from the owner:Thank you, Layton, for your amazing review! We really appreciate your support and hope to be your first call for any future repairs!
Same day service. Technician arrived as scheduled. Replaced capacitor quickly. Friendly technician. Repair cost $429 seemed high for inexpensive part and 20 minutes labor.
Response from the owner:Thank you, Tom, for your feedback! We're glad to hear the technician was prompt and friendly, though we understand your concerns about the repair cost. We appreciate your insights and hope to serve you again in the future.
Response from the owner:Thank you so much, Al, for your excellent review; we truly appreciate your support and are glad to hear you had a great experience!
Thomas Hoffmann is the most professional and courteous of all the HVAC companies in St. Louis. It has kept my HVAC systems in good working order through the hottest and coldest days for many years.
Response from the owner:Thank you, Jonathan, for your kind words about our professionalism and courtesy; we truly appreciate your support!
I notified two companies at the same time regarding a malfunctioning AC unit and Wow! Super fast response from Hoffmann on a weekend no less, to fix our AC unit. Hoffmann’s tech responded to my call immediately and fixed our AC before Galmiche has even responded. Used to be a Galmiche customer, but will use Thomas Hoffmann from here on out!
Response from the owner:Thank you, Darlene, for your fantastic feedback! We're glad to hear that our team was able to respond quickly and resolve your AC issue. We appreciate your trust in us moving forward!
Ryan did a great job with my AC reinstall. Very knowledgeable company with Tom Hoffmann providing the engineering expertise.
Response from the owner:Thank you, Steve! We're glad to hear that Ryan did a great job on your AC reinstall, and we appreciate the shoutout to Tom's expertise. Your satisfaction means a lot to us!
These guy's are amazing same day service very well priced for the knowledge they have ask before doing anything to confirm they're my new go to
Response from the owner:Thank you, Cory! We're glad you found our service amazing and appreciate your kind words about our pricing and knowledge. We're here for you anytime!
⚠️ 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.
