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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 peter in Whitby on Twintech Heating and Cooling

Very impressed with this company. They show up on time , kept my place clean and after they left it looks like they were never there. Very professional team. Those people know what they doing . Their installation was on the highest standard. They are very knowledgeable especially they're worker Peter. I strongly recommend this company to everybody. After the installation I receive the call making sure I'm satisfied with their products and their job. Bravo!!!

by James in Bowmanville on Twintech Heating and Cooling

Greg and his brother were referred to us by a friend. They arrived when they said they would, did an exceptional job and left the place as tidy or tidier then they found it. Their professionalism is only surpassed by their kind and friendly demeanor. Even after several calls to help me with my high tech thermostat I feel that I could always call with any concern (No one responds to my texts as quickly as Greg) and have a friendly helpful response. I found out their grandfather started the company and now as a 3rd generation company, they are doing their grandfather proud. I would highly recommend Twintech over any other hvac company out there.

by RJW in Ajax on Twintech Heating and Cooling

Thanks to the guys at Twintech Heating for a great job installing a new hot water tank. They set a time and day to remove the old tank and install the new one. They were on time and had the work done quickly and cleaned up after they were finished. Excellent work and great value.

by Marilyn in Milton on Twintech Heating and Cooling

In November, we contacted Twintech for a quote on a high efficiency furnace plus installation. Dave, the sales representative for the company was very friendly and informative. Upon arrival at our home, he willingly showed us his company licenses, clearly explained the operation of a high efficiency furnace and answered all our questions to our satisfaction. As well, Dave was the only sales representative that we contacted that was willing to make the arrangements for an energy audit. For us, this was a big plus as we found the government rebate program somewhat confusing to navigate. The furnace was installed on the date that was arranged in an efficient and professional manner by Greg (the owner) and Peter. Both men worked diligently, throughout a long day to complete the job and upon finishing, left the job site immaculate. When a neighbour raised concerns about the furnace venting location, Greg located an alternative location and resolved the situation with diplomacy. We chose the Napoleon furnace for its excellent warrant;y on the heat exchanger and because it was made in Canada! In addition, to the furnace warranty, Twintech offered us a 5 year warranty on labour which speaks to the quality and pride this team has in their workmanship. It has been over a month now (with some of the coldest January days on record) since we have had the furnace installed. The furnace runs quietly and distributes heat more evenly throughout our 90 year old Toronto home. We can't speak highly enough of the Twintech team and are very satisfied with their workmanship and job ethics. We have no hesitation about recommending them.

by Barry in Toronto on Twintech Heating and Cooling

What more could you ask for! Grant and Greg Dainty provided a professional,diligent and thorough approach to the installation of my furnace. I would highly recommend there services.

by Hector in Scarborough on Twintech Heating and Cooling

Last week our Furnace failed overnight. We called Twintech to help us get it running again. They did a really thorough check on it, and got it running in less than an hour. Given that it was an old Furnace (+20 years old), we were giving two options: repair it or replace it. Instead of doing a repair on it that could break in a week or two, they recommended us to change it. I like that they were honest on the recommendation, not forcing a new furnace on us. At the end we went with a new Furnace. Twintech solutions service & salesman gave us recommendation on the size of the unit and many options that could work for our home. They ended up doing an excellent work in our furnace, replacing the filter to a better option and replacing some pieces that had water damage. They cleaned after themselves and leave everything even better than what they found. They even went far and beyond tiding up the hose connections that we had on the basement.

by Ryan Doherty in Whitby on Twintech Heating and Cooling

I am in the process of finishing my basement and wanted to make sure I got the low hanging duct work fixed in advance. After reviewing 5 quotes I selected Twintech to award the contract to. The price was competitive however what won me over was Grant's (co-owner) attention to detail and his ability to focus on what my goals and priorities were for the project. His team completed the job over 3 days as there was significant duct work changes and the relocation of all of the equipment. They also completed the job with little downtime so we weren't left overnight without heat during freezing winter temperatures.

by Private User from Oshawa on Twintech Heating and Cooling

My father woke up to no heat one Saturday morning. We had a few names that friends had recommended but while checking out the companies' ratings on HomeStars, we found Twintech with great ratings too. The other companies either didn't get back to us or didn't have time to come at such short notice. TwinTech made the time in their schedule for what they judged to be an emergency: no heat in the home of an elderly person. At no extra fee for a short notice, weekend visit. They recommended an upgraded furnace unit and explained that we would qualify for a rebate that would bring the price down to that of a lower model. They set us up with the rep from the MNR that covers the rebate so that we didn't have to deal with the paperwork & phone calls ourselves. Installation was quick, efficient, & smooth. We were so pleased with their service we ordered a new water heater too. Both are working great (efficient & quiet!) & my father is safe & comfortable. We can't say enough about how pleased we are with their service. We have already recommended them to others.

by joe calabro in Pickering on Twintech Heating and Cooling

Twintech Heating & Cooling. I just want to say thanks for helping me . My Furnace stopped working. And l phone Dave Getgley he set me up with Greg. What an amazing team they did a great job in setting me up with a new Furnace. Anyone that needed a new Furnace these are the guys to call. Thanks again for a job well done.

by Peter from Ajax on Twintech Heating and Cooling

Our home has had poor heating and air conditioning the past couple of years. Dave recommended a Goodman solution with more power than we had. Grant and Greg installed the units in late November. Heating is better than ever. We have a warm home again and look forward to the winter. Can't wait to see how the AC runs in 2018. Job was super clean and professionally done. Highly recommended.

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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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