You’ve just moved into an apartment in the Plateau or Rosemont, and despite the incredible charm of those old brick walls, there’s that smell. A musty, damp smell—like air that hasn’t circulated since 1975. You open the windows, light some candles, mop the floors—nothing changes.
You’re definitely not alone. According to data from the City of Montreal, about 35% of the city’s residential buildings are over 50 years old. And with age come problems with ventilation, moisture, and indoor air quality—all of which contribute to these stubborn odors.
In this article, We'll explain where these bad odors come from, how to identify them, and most importantly—how to get rid of them for good.
The Main Causes of Bad Odors in Old Buildings
Montreal’s old buildings certainly have character. But they also have ventilation systems from a bygone era, insulation problems, and a complicated relationship with moisture. Here’s what’s really going on behind those odors.
Moisture and Condensation—The Hidden Duo Behind Mildew
In winter in Montreal, when it’s -20°C outside and 22°C inside, condensation forms everywhere: on windows, in poorly insulated walls, and around door frames. This moisture builds up, and with it come musty odors.
According to the Institut national de santé publique du Québec (INSPQ), between 20 and 30% of older homes in Montreal have humidity levels above 60%—well above the recommended range of 30 to 50%. When humidity rises, mold grows. And mold really doesn’t smell good.
If you have a hygrometer at home, check the humidity level. Is it over 60%? That’s a problem. Don’t have one? You can get one for 15$ at the hardware store, and it’s worth it.
Have the humidity level in your condo tested—free inspection with Vortex Air. We come to take measurements, assess the situation, and tell you exactly what's going on. Call 514-214-7492 or visit vortexair.ca.
Mold and Spores — When Walls Don't Breathe Properly
Mold loves three things: moisture, heat, and stagnant air. In old buildings with poor ventilation, it finds a paradise.
The INSPQ estimates that up to 70% of unpleasant odors in older homes stem directly from the presence of mold spores in the air. These spores spread through the vents, become embedded in carpets and curtains, and continue to emit an odor even if you clean the visible surfaces.
The problem is that mold often hides behind walls, under floors, and in ceilings. You can’t see it, but you can smell it. And if you have black or green spots on the walls, water stains, or areas where the paint is blistering, that’s a clear sign that there’s mold somewhere.
Radon and Air Infiltration — The Invisible Danger in Basements
Radon is a radioactive gas that seeps naturally from the ground into buildings. It has no odor of its own, but it is often accompanied by other gases from the ground that do have a bad smell—like the smell of damp earth, a basement, or a musty room.
According to Santé Québec and the Montreal Regional Public Health Directorate (DRSP), between 8 and 15% of downtown buildings have radon levels that are cause for concern, especially in poorly ventilated basements and half-basements.
If you live on the ground floor or in the basement of an older building and it smells like a basement even in the middle of summer, have your home tested for radon. The DRSP offers free test kits. It’s simple, takes three months to measure, and could save your life—literally.
Outdated ventilation ducts and odor recirculation
Ventilation systems installed in the 1960s and 1970s were never designed to meet today’s standards. Many older buildings don’t even have a heat recovery ventilation (HRV) system. Air doesn’t circulate properly, odors linger, and when the ducts are clogged with 30 years’ worth of dust, everything that smells bad gets recirculated.
According to the Régie du bâtiment du Québec (RBQ), professional duct cleaning can reduce persistent odors by 60% as early as the first year. It’s not magic—it’s simply a matter of removing the source of the problem.
Schedule a thorough duct cleaning with a certified technician. Vortex Air serves the entire Greater Montreal area to inspect your system for free and offer you tailored solutions. 514-214-7492 or vortexair.ca.
How to Identify the Source of a Bad Odor in an Old Building
Before spending hundreds of dollars on cleaning, take the time to figure out where the smell is coming from. It could save you a lot of trouble.
Visible and Olfactory Signs
Start with a visual inspection. Here's what you should check:
Walls and ceilings: Look for water stains, black or green marks, and areas where the paint or wallpaper is peeling. If you see bubbles, it means moisture is building up behind them.
Around the windows: Is there condensation? Is the window frame rotten or discolored? That's often where moisture gets in.
Under the sinks and in the bathroom: Open the cabinets and look under the sink. If it smells strong and feels damp, there may be a leak or a ventilation problem.
Ventilation ducts: Open a vent and look inside with a flashlight. If you see black dust, signs of mold, or if you can smell something coming from there, your ducts need attention.
You should also use a hygrometer to measure the humidity level in each room. Is it over 60%? Then you have a humidity problem that’s causing odors.
Recommended Professional Tests in Montreal
If you can't find the source on your own, call a professional. There are several types of inspections available in Montreal:
Radon testing: The DRSP offers free test kits. You use them for 3 months, return them, and receive the results. It's simple and free.
Indoor Air Quality (IAQ) Audit: Companies such as Benjel Consultants and Vortex Air can perform a comprehensive inspection of your ventilation system, test CO2 levels, measure humidity, and identify sources of contamination.
Thermographic inspection: An infrared camera can show where cold air is entering, where moisture is accumulating in the walls, and where thermal bridges are causing condensation problems.
Schedule your QAI inspection today — local service available 24/7. Vortex Air responds quickly, assesses the situation, and provides you with clear, no-pressure recommendations. Call 514-214-7492 or visit vortexair.ca.
Practical Solutions for Eliminating Odors in Older Buildings
Once you know where the problem is coming from, it's time to take action. Here's what really works.
Improving Air Quality: Duct Cleaning and Decontamination
If your ducts are clogged, no matter what you do, it will only mask the problem temporarily. You have to clean them at the source.
Professional ventilation duct cleaning isn't just about vacuuming the grates. It's a multi-step process: a thorough inspection using a camera, mechanical cleaning of the ducts with rotating brushes, industrial vacuuming with HEPA filtration, and antibacterial treatment if necessary.
According to Chapter V of the Quebec Building Code (2025 update), buildings more than 10 years old should have their ventilation systems inspected regularly. This isn’t just a recommendation—it’s a safety standard.
At Vortex Air, our process is simple and transparent: we conduct a free inspection, show you what we find, clean using INVC-certified equipment, and perform a final test to confirm that the air is clean.
Get a free quote for a complete cleaning — Vortex Air, INVC-certified experts. We'll explain everything to you, show you the results, and work within your budget. 514-214-7492 or vortexair.ca.
Monitor Humidity and Ventilation on a Daily Basis
If you don't want the odors to come back, you need to control the humidity. Here's what you can do:
Installing a dehumidifier: In basements and damp rooms, a good dehumidifier can make all the difference. Aim for a humidity level between 30 and 50%.
Use a heat recovery ventilator (HRV): If your building doesn't have one, now is the time to bring it up with your landlord or homeowners' association. A VRC refreshes the air without losing heat. It's a game-changer for older buildings.
Ventilate Smartly: Open the windows for 10–15 minutes a day, even in winter, to let out any built-up moisture. Avoid doing this when it’s too cold (below -15°C), because it causes more condensation.
Good news: Transition énergétique Québec (TEQ) is offering grants of up to 2,000$ for the installation or replacement of ventilation systems in 2025. The return on investment is estimated to be between 3 and 5 years, thanks to energy savings and improved air quality.
Renovating Without Losing the Building’s Historic Character
Do you live in a historic building? You can improve ventilation and insulation without detracting from the building’s charm. There are solutions available that are compatible with older structures.
The City of Montreal’s RénovPatrimoine program offers grants ranging from 1,000$ to 5,000$ for heritage-sensitive renovation work, including improvements to ventilation and insulation using natural materials (rock wool, hemp, cellulose).
Consult the City of Montreal’s Heritage 2025 guide to learn about eco-friendly solutions compatible with stone, wood, and brick structures.
Common Myths About Old Buildings and Their Odors
We've all heard advice from our grandmothers or read tips online. Here's what's true, what's false, and what deserves some clarification.
«It's just plumbing» — Wrong!
Yes, a plumbing leak can smell bad. But in most older buildings, the smell comes from a combination of factors: moisture, mold, and clogged pipes. If you fix the plumbing and it still smells, the problem lies elsewhere.
«Vinegar cures everything» — Partially true
White vinegar is effective at cleaning surfaces and killing surface mold. But it doesn't work on mold inside walls or in ducts. Use it as a supplement, not as a standalone solution.
«Winter = dry air» — False—condensation is on the rise!
Many people think that winter dries out the air. In reality, in a poorly ventilated home, moisture produced by breathing, cooking, showering, and drying laundry builds up and causes condensation everywhere. Winter is often worse when it comes to indoor humidity.
Before trying 10 homemade recipes, request a free inspection. Vortex Air can pinpoint the true source of the problem in 30 minutes and save you months of frustration. 514-214-7492 or vortexair.ca.
Assistance Programs and Grants Available in Montreal
Improving air quality in an older home can be expensive. Fortunately, there are several financial assistance programs available in Quebec.
Transition énergétique Québec (TEQ): Grants of up to 2,000$ for the installation or replacement of energy-efficient ventilation systems (HRVs, heat recovery ventilators).
RénovPatrimoine (City of Montreal): Financial assistance ranging from 1,000$ to 5,000$ for heritage-sensitive renovation work, including improvements to ventilation and insulation.
Montreal DRSP: Free radon test kits for all residents. Results in 3 months.
Find out if your building is eligible—free assistance from Vortex Air. We'll help you navigate the programs, fill out the forms, and maximize your grants. Call 514-214-7492 or visit vortexair.ca.
Why Choose Vortex Air for Your Older Building in Montreal
We know Montreal's old buildings inside and out. We know how they're built, where the problems lie, and how to fix them without destroying the building's charm.
Vortex Air has over 10 years of combined experience in residential and commercial ventilation cleaning. We’ve worked in century-old triplexes on the Plateau, renovated condos in Griffintown, and historic buildings in Rosemont. We’ve seen just about every problem imaginable.
We are INVC-certified and in the process of obtaining NADCA certification—standards recognized throughout the industry. Our team of more than five trained technicians works with respect, professionalism, and transparency.
Our 3-step process: Free inspection (We'll evaluate your system at no charge), Professional Cleaning (rotating brushes, HEPA filtration, antibacterial treatment), Air Quality Report (We'll show you the before-and-after results.).
We have over 500 satisfied customers in the Montreal area. We're available 7 days a week, from 7 a.m. to 9 p.m. We speak French and English. And we never pressure you into buying services you don't need.
Call our local experts—breathe easier starting this week. 514-214-7492 or vortexair.ca. Because everyone deserves clean air, even in a 1952 apartment.
FAQ — Odors and Air Quality in Older Buildings
How can I tell if the odor is coming from the vents or the walls?
Open a ventilation grille and take a direct whiff. If the smell is stronger there, it’s coming from the ducts. If the smell is constant everywhere, even when the ventilation is off, check the walls, windows, and damp areas. A hygrometer can also help—a humidity level above 60% is a sign that the walls are retaining water.
Is vinegar effective against mold?
Yes, but only on visible surfaces. Diluted white vinegar (1 part vinegar to 3 parts water) kills about 80% of surface mold. However, it does nothing against mold in walls, ceilings, or ducts. Use it as a first step, not as a complete solution.
What should you do if the landlord refuses to allow repairs?
If you are a tenant and your landlord refuses to perform repairs that are essential for indoor air quality, contact the Administrative Housing Tribunal (TAL, formerly the Régie du logement). You have the right to safe and healthy housing. Document everything: photos, humidity readings, and witness statements. Keep copies of your written requests to the landlord.
Are HEPA filters sufficient in winter?
HEPA filters are very effective at capturing fine particles, dust, and mold spores. But if your ducts are dirty or your ventilation system isn't working properly, a filter alone won't solve the problem. You need a combination of high-quality filters, clean ducts, and good ventilation.
Where can I request a free radon test in Montreal?
The Montreal Regional Public Health Directorate (DRSP) offers free radon test kits. You can order them on their website or call their health information hotline. The test takes 3 months (measurements must be taken over a long period to ensure reliable results), and you’ll receive the results by mail.
Which grants cover ventilation?
Transition énergétique Québec (TEQ) offers up to 2,000$ for the installation of energy-efficient ventilation systems such as HRVs. The RénovVert program also covers certain air quality improvement projects. And if your building is a heritage property, RénovPatrimoine can provide you with between 1,000$ and 5,000$ for heritage-sensitive renovations.
What is the difference between a dehumidifier and a heat recovery ventilator (HRV)?
A dehumidifier removes moisture from the air, but it doesn't replace the air itself. It's good for basements, bathrooms, and enclosed spaces. A HRV (heat recovery ventilator), on the other hand, replaces stale air with fresh air from outside while retaining heat. It’s a more comprehensive solution for your entire house or condo. Ideally, you should combine the two.
Are you tired of smelling mold in your old apartment? We get it. It’s not just unpleasant—it’s bad for your health and your family’s health. Vortex Air is here to help—with honesty, local expertise, and a genuine respect for your budget.
Call us at 514-214-7492 (available 24/7) or visit vortexair.ca To reserve your Free inspection, no pressure. We serve the entire Greater Montreal area, including the North Shore and South Shore. Because even in a building from the 1960s, you deserve to breathe clean air.
