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How Heating Systems Affect Indoor Air Quality

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How Heating Systems Affect Indoor Air Quality

Posted On: February 17, 2026

How Heating Systems Affect Indoor Air Quality

When winter hits, your heating system becomes one of the most important pieces of equipment in your home.


But beyond keeping you warm, it also plays a major role in something many homeowners overlook: indoor air quality (IAQ).


Poor indoor air quality can lead to dry air, allergy flare-ups, headaches, lingering odors, and even long-term health concerns.


Understanding how your heating system affects the air you breathe is the first step toward a healthier, more comfortable home.


Below, we’ll break down how different heating systems impact indoor air quality, common winter air problems, and what you can do to improve the air inside your home.


Why Indoor Air Quality Matters in Winter


During winter, homes are sealed tightly to keep cold air out and heat in.


While this improves energy efficiency, it also means:


Less fresh air circulation


More trapped dust, allergens, and pollutants


Increased dryness from constant heating


Your heating system continuously circulates air throughout your home, which means it can either help clean the air—or spread contaminants if it isn’t properly maintained.


How Forced-Air Heating Systems Affect Air Quality


Forced-air systems (furnaces and heat pumps) are the most common residential heating systems.


These systems heat air and distribute it through ductwork and vents.


Positive Effects


Air passes through filters, which can remove dust, pollen, pet dander, and debris


Can be paired with air purifiers, humidifiers, and high-efficiency filters Negative Effects


Dirty ducts can circulate dust, mold spores, and allergens


Old or clogged filters reduce air quality and airflow


Leaky ductwork can pull contaminants from attics, crawl spaces, or basements


Key takeaway: A forced-air system can greatly improve indoor air quality—but only if filters, ducts, and components are properly maintained.


Heating Systems and Dry Indoor Air


One of the most common winter complaints is dry indoor air.


Heating systems don’t add moisture to the air, and warm air holds less humidity than cool air.


Low humidity can cause:


Dry skin, eyes, and sinuses


Increased static electricity


Cracked wood floors or furniture


Worsened cold and flu symptoms


This isn’t a system “failure,” but a natural side effect of heating.


Whole-home humidifiers or portable units can restore proper moisture levels and improve comfort significantly.


Furnaces and Combustion Byproducts


Gas and oil furnaces rely on combustion to produce heat.


When working properly, combustion gases are safely vented outside.


When they’re not, indoor air quality can suffer.


Potential issues include:


Carbon monoxide leaks


Nitrogen dioxide exposure


Burning or musty odors


Cracked heat exchangers, blocked flues, or poor ventilation can all create safety risks.


This is why annual furnace inspections are critical—not just for performance, but for health and safety.


How Heating Systems Impact Allergies and Respiratory Issues


Heating systems can aggravate allergies and asthma if indoor air quality isn’t controlled.


Common triggers include:


Dust buildup in ductwork


Mold growth in humid or neglected systems


Pet dander recirculating through vents


Dirty air filters


If someone in your household experiences worsening allergy symptoms in winter, your HVAC system may be part of the problem—and part of the solution.


Upgrading filters, improving humidity control, and scheduling regular maintenance can drastically reduce airborne irritants.


The Role of Air Filters in Indoor Air Quality


Your HVAC filter is the first line of defense against poor indoor air quality.


Low-quality or clogged filters:


Allow particles to circulate freely


Reduce airflow and system efficiency


Increase wear on your heating equipment


High-quality filters (with higher MERV ratings):


Capture smaller particles like pollen, mold spores, and fine dust


Improve air cleanliness


Protect HVAC components


However, higher-rated filters must be changed regularly to avoid airflow issues.


Most homes should replace filters every 1–3 months during heating season.


Ductwork: The Hidden Factor


Even the best heating system can’t maintain good air quality if the ductwork is neglected.


Problems inside duct systems may include:


Dust accumulation


Mold growth due to moisture


Pest debris


Air leaks pulling in contaminants


Sealing, cleaning, and inspecting ductwork helps ensure that only clean, conditioned air is delivered throughout your home.


How to Improve Indoor Air Quality During Heating Season


If you’re concerned about winter air quality, here are practical steps homeowners can take:


Change HVAC filters regularly


Schedule annual furnace maintenance


Use a whole-home humidifier if air feels dry


Keep vents and returns clear


Seal duct leaks and address insulation issues


Consider indoor air quality upgrades like air purifiers or UV systems


These improvements not only make your home healthier but can also boost heating efficiency and comfort.


When to Call a Professional


If you notice:


Persistent dust buildup


Unusual odors when the heat runs


Excessively dry air


Allergy symptoms worsening indoors


Uneven heating or poor airflow


…it’s time to have your HVAC system professionally inspected.


Many indoor air quality issues stem from hidden mechanical or airflow problems that only trained technicians can properly diagnose.


Final Thoughts


Your heating system does far more than warm your home—it directly affects the quality of the air you breathe every day.


With proper maintenance, filtration, and humidity control, your HVAC system can support a healthier indoor environment all winter long.


At Twintech Heating & Cooling, we help homeowners stay comfortable while protecting their indoor air quality.


If you’re concerned about your heating system or winter air quality, professional maintenance and upgrades can make a noticeable difference.



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See What Our Customers Are Saying:

by Jiri in Toronto on Twintech Heating and Cooling

From the initial contact we had an excellent experience with this company and all its personnel. Dave Gergley was an excellent, helpful, sales person and solicitous of our needs. He recommended only what was required and did not up sell or make any suggestions for products that we did not need, such as a new A.C. He explained the rebate process and basically outlined how to get the best furnace at the lowest price. When it was time for installation, the technicians could not have been more considerate, careful, attentive to detail, obviously committed to safety and optimum functioning of the appliance they were setting up. We have been perfectly satisfied with the functioning of the furnace and all aspects of acquiring it from the initial contact with Dave through to the installation process and follow ups inquiring about our satisfaction. Also they initiated the rebate process and contacted the appropriate inspection agency to carry it out. We highly recommend this company for all heating and cooling needs and we will contact them again when it is time to replace our A.C.

by Drew in Pickering on Twintech Heating and Cooling

Twintech was excellent from the initial quote and throughout the install. They had a competitive rate for hot water tank and ended up buying the tank from them, had them remove the old tank and install the new one. The day of install they were prompt and out in about 2 hours. Professional , courteous really great guys. We took a look at my 30 year old furnace and they were able to offer some suggestions for future there too.

by Harry in Toronto on Twintech Heating and Cooling

Ever since I turned on my furnace on Oct 2018 I hear a humming sound when the furnace fan kicks in. I called Adamson Air System who installed my furnace 7 years ago and couldn't figure it out the problem. I just wasted money to the guy who couldn't figure it out. I found Twin Tech via Amana / Goodman website. I checked the reviews from previous Twin Tech customers. I called Greg and was onsite on time this morning Sunday, Nov 25 2018. He figured it out what's wrong with the furnace and explained what the previous installer (adamson air system) did wrong when they installed it. His knowledgeable about his job. He recommend to replace the fun motor because the sound is not normal when it's running. Looking forward to see him again to replace the fan motor.

by Roger in Pickering on Twintech Heating and Cooling

Our house is over 22 years old and I had been researching furnaces and A/C brands for a while and thought it was time to take the plunge. After calling three different companies to come in and quote the job, this one won me over. From the first visit from Dave all the way to the end of the install by Greg, Grant, and Piotr, I was glad to have picked this company. Dave was very knowledgeable and really took the time to explain what kind of quality installation I was going to get as well as showing me some of their previous work and certificates.

I was also surprised at how quick the installation took and how nice everything looked afterward, I mean it's only a furnace right? They even re positioned the furnace so that I have easier access to my filter and humidistat, awesome! If you are looking for a company that cares about their customers and is proud about the quality of work they do, along with a great and competitive price, then stop right here because you found it.

by Louis in Pickering on Twintech Heating and Cooling

Once our AC Unit started to fail, I called our past Heating & Cooling provider for support. The response was we needed a new motor for our Furnace. It was time to check their Quote against the marketplace, I reached to other providers online. One of the owner of Twintech (Greg), called me and offered a preliminary Quote and recommendation online. The others needed to set an appointment and came to measure and spend 1 hour before offering a quote. Then I asked Twintech to come finalize their quote to make sure their recommendation was aligned and met our needs.

Twintech was professional throughout the process, easy to deal with (Web, Phone and in Person), price right and met their commitment. Their team expedited the process and installation, arranged for a energy assessment for available rebates and most importantly, delivered on their commitment and managed to do a few extras. They installed a New Furnace, AC unit and Nest thermostat in a day, remove all older units, left the house and outdoors clean and without any debris. Great to be able to support a Local Company, Neighbour and Professional team - Well Done Team Twintech !!!

by Elizabeth and John L from Scarborough on Twintech Heating and Cooling

In October 2018, I contacted Greg at Twintech to do a furnace cleaning. Greg discovered that my furnace, installed in 2006 by another company, had been installed incorrectly, leading to restricted air flow. The heat exchanger was also defective. As well, my furnace was too large for the size of my house.

In my opinion, the biggest concern most of us have as consumers is that we have no idea of the quality or knowledge and experience of the technicians any heating and cooling company will send into our homes. I could have avoided having my 2006 furnace installed improperly (leading to early replacement), had I known about Twintech then.

With Twintech you get it all. Because Twintech is a smaller company you can rest assured that the only technicians who will work in your home are Greg and his twin brother Grant who are co-owners and fully licensed and certified with over 30 years of experience in installing and servicing heating and cooling equipment. They are both friendly and personable and answer all your questions. Their workmanship is outstanding. We had a 2 stage, variable speed Goodman furnace installed. My wife and I noticed a difference in the heating and even temperature of our 2 storey home almost immediately. Our old furnace always heated too much on the main floor and too little upstairs. We are also impressed with how quiet the furnace is.

Twintech's office manager, David Gergley, is equally friendly and not only gave us a competitive quote to replace our furnace (we sought other quotes), but also went above and beyond my expectations when he made arrangements with an energy audit company so that we would be considered for a grant from Enbridge and IESO.

Needless to say, I give Twintech a 10 out of 10 and highly recommend them!

by James, Ajax on Twintech Heating and Cooling

Clean, Fast and Efficient Work. Between all the quotes I received Twintech was a few dollars less and offered the best warranty.

by garysumnec360, Whitby on Twintech Heating and Cooling

They did an excellent job. Everything was very well explained. At the end of the job everything was very well cleaned up.

by Glade, Pickering on Twintech Heating and Cooling

Twintech offered me a competitive price but more importantly great sales and installation service. They did everything with attention to detail and quality workmanship that is hard to find in this day and age. Dave who first game to visit me answered most of my questions and probed about my needs. For the technical/install questions he was unable to answer he quickly had Greg and Grant the owners answer for me. They did not cut corners on the installation or do anything to simply save time. They stayed into the early evening to complete the job and removed all my old components and even fixed up mistakes other workers ahd made in the past. I would highly recommend them and use them again if the need arises in the future. If you are looking for service or new equipment I would highly recommend Twintech be on your list of Heating companies to get a quote from and ask your questions to.

by Anne of Major Oaks in Pickering on Twintech Heating and Cooling

The company epitomizes high quality service: from the initial client interaction with Dave to the installation and follow up with the technical team. One of the key features I look for is the ability of a technical person to talk to and not talk down to the customer when responding to questions and I had quite a few, all of which were very professionally addressed. I was also quite impressed with the follow up service, promptness, the obvious competence of the team who left no stone un-turned to ensure I was a satisfied customer. Thank you guys.

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See What Our Customers Are Saying:

by Aaron on Twintech Heating and Cooling

We are very happy to recommend this company to everyone. Our furnace broke down on Sunday morning. We phoned them and before noon Grant the owner showed up. He worked on the furnace for about a hour not wanting to give up to fix the problem. The furnace was 17 years old. I was the one talking about replacing it. End result was the next day it was all done. On the Sunday Bob came over with heaters to warm up the house. We decided to replace the water heater at the same time. Thanks Grant for the excellent work. Thumbs up.

by Linda on Twintech Heating and Cooling

Right on time. Explained how to work the HRV in a different way so the house would not be so dry. Changed my whole house water filter for me as well. Friendly, helpful, caring service!

by Robert Rogers on Twintech Heating and Cooling

Very pleased with the professional service that TwinTech Heating and Cooling provided in replacing my furnace. I got several quotes from different service providers. Their price was excellent and they explained the features very well. We are very glad we went with TwinTech and highly recommend their services.

by Robert Mizuno on Twintech Heating and Cooling

We were new homeowners in need of a second opinion. TwinTech Heating & Cooling were Amazing and professional. Very knowledgeable and great service all around. Recommend to anyone looking for honest and reliable services. Treated with respect and care. Thank you Greg, Mitch and Bob!

by Ruth on Twintech Heating and Cooling

TwinTech is an excellent and honest company! I called them for a second opinion after being told by another company that I needed to replace my furnace. Turns out this was not the case at all! I did not need a new furnace. TwinTech did not push to make an unnecessary sale and saved me from a huge expense. Bob and Mitch were extremely professional and above all honest! I definitely recommend TwinTech!

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