Seasonal allergies in St. Louis? Your HVAC system might be making symptoms worse. Learn the signs and how to improve indoor air.
A poorly maintained or outdated HVAC system can circulate dust, pollen, pet dander, mold spores, and other airborne allergens throughout your home. In this post, we’ll walk through the key signs that your HVAC system is aggravating allergies, why it happens, and how you can take action to create a cleaner, healthier home environment.
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.
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.
Response from the owner:Hi there. I am unable to locate your customer profile. Please give our office a call at 314-471-7625 so we can get this figured out for you.
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!
1. You’re Experiencing Allergy Symptoms Indoors — All Year Long
If you notice that allergy symptoms persist regardless of the season, your indoor air quality may be the culprit. Common indoor allergy symptoms include:
Sneezing
Runny or stuffy nose
Itchy eyes or throat
Skin irritation
Frequent headaches
Your HVAC system could recirculate airborne irritants like dust mites, mold, or dander. Without proper filtration and regular maintenance, allergens can thrive inside your home and your ductwork.
2. You Notice Excessive Dust Around Vents and Furniture
A telltale sign of a compromised HVAC system is a noticeable layer of dust, especially near air vents. If dust builds up quickly after cleaning, your system may not filter the air effectively. This can happen if:
Your HVAC filter is clogged or of too low quality (e.g., low MERV rating)
Your ductwork is dirty or leaking
Your air returns are pulling in unfiltered air from dusty areas like attics or crawl spaces
This dust isn’t just a nuisance — it’s a vehicle for allergens like pet dander and pollen to circulate through your home.
3. Your Air Filter Is Dirty (or You Can’t Remember the Last Time You Changed It)
Your HVAC filter is your home’s first line of defense against allergens. But if it’s clogged or outdated, it can no longer effectively trap particles. It can restrict airflow, forcing your system to work harder and potentially blowing allergens into your home.
We recommend St. Louis homeowners:
Change filters every 1–3 months
4. A Musty or Moldy Smell is Coming from the Vents
If your HVAC system smells musty, it could indicate mold growth inside the ductwork, air handler, or evaporator coils — all of which can significantly worsen respiratory symptoms.
Mold thrives in humid environments, which is common in St. Louis, especially in spring and summer. Your HVAC system may be contributing to this problem if:
The condensate drain line is clogged
There’s excess moisture in your ductwork
Your home lacks proper dehumidification
A professional inspection can help detect and remove mold sources before they become a health hazard.
5. You Hear Unusual Noises or Your System Runs Constantly
An overworked or aging HVAC system may struggle to regulate temperature and humidity, creating ideal conditions for allergens to flourish. If your system runs nonstop or makes banging, rattling, or squealing sounds, it may not distribute air evenly or filter it effectively.
This can result in stale, poorly ventilated indoor air that traps allergens instead of removing them.
6. Your Humidity Levels Are Out of Balance
Humidity plays a major role in indoor air quality:
Too much moisture (>60%) can fuel mold, mildew, and dust mites.
Too little humidity (<30%) can dry out mucous membranes and worsen allergic reactions.
In St. Louis, homes often swing between humid summers and dry winters. Your HVAC system should help regulate indoor humidity, but if it doesn’t, consider a whole-home humidifier or dehumidifier.
7. You Haven’t Had Your Ducts Cleaned in Years (or Ever)
Over time, your ductwork can become a hidden hotspot for dust, mold, pollen, and even insect debris. Your system can blow those allergens back into your living spaces every time it runs.
If it’s been years (or decades) since your ducts were cleaned, you may benefit from a professional duct cleaning, especially if:
You have pets
You’ve recently renovated
You’ve moved into an older home
How to Allergy-Proof Your HVAC System
The good news? You don’t have to live with allergy-aggravating air. Here are simple yet powerful steps you can take:
Upgrade your air filter to at least MERV 11.
Schedule seasonal HVAC maintenance (spring and fall are ideal).
Install a whole-home air purifier or UV air scrubber.
Seal and clean your ductwork to eliminate hidden allergen sources.
Balance your humidity levels with a humidifier or dehumidifier.
Keep your home well-ventilated, especially bathrooms and kitchens.
Trust the Local Indoor Air Quality Experts in St. Louis
At Thomas Hoffmann Air Conditioning & Heating, we’ve helped hundreds of St. Louis families improve their home’s air quality and reduce allergy triggers, boosting energy efficiency and comfort. Whether you need a filter upgrade, duct cleaning, or a full IAQ solution, our licensed technicians are here to help.
Breathe Easier. Live Better.
Contact us today to schedule a free indoor air quality consultation. With local expertise you can trust, we can create a healthier, allergen-free home together.
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