Does your child come home from school tired and with frequent headaches? Does he or she cough more often at home than when out and about?
It might not just be a lingering cold. It might be the air he's breathing.
Indoor air can be 2 to 5 times more polluted than outdoor air. In Montreal, between urban smog, smoke from wildfires—which have become an annual occurrence—and poorly ventilated older buildings, our children spend 90 % of their time in spaces where the air quality is often poor.
Children are more vulnerable than adults. They inhale more air per kilogram of body weight. Their lungs are still developing. And they spend their days in schools and daycare centers where CO₂ levels regularly exceed recommended thresholds.
This article explains why indoor air quality directly affects your children’s health and learning, what’s really happening in Montreal schools and homes, and, most importantly, what you can do to protect your family.
Why Indoor Air Quality Is Critical for Children
Children aren't just miniature adults. Their bodies function differently. And when it comes to indoor air pollution, that difference can have serious consequences.
Children breathe in more… and filter out less
A child breathes faster than an adult. A child inhales proportionally more air relative to their body weight—up to 50 % more.
This means that, at the same concentration of pollutants, a child absorbs much more fine particulate matter, CO₂, and volatile organic compounds than an adult in the same room.
Their lungs continue to develop until they are 18 years old. Their airways are narrower, making them more susceptible to inflammation caused by pollution.
According to UNICEF, indoor and outdoor air pollution contributes to approximately 237,000 deaths of children under the age of 5 each year worldwide. This is a major public health issue, even in developed cities like Montreal.
Fine particulate matter (PM2.5) penetrates deep into the lungs. In children, it can permanently affect lung development and increase the risk of asthma, chronic bronchitis, and recurrent respiratory infections.
Measured Impacts on Health and Learning
Indoor air quality doesn't just affect the lungs. It also affects the brain.
Studies published in ScienceDirect show that when CO₂ levels in a classroom exceed 1,000 ppm (parts per million), students’ ability to concentrate decreases measurably. Their reaction times slow down. Their cognitive performance declines.
In Montreal, CO₂ levels at several public schools and early childhood centers (CPEs) have been measured at levels that regularly exceed 1,050 ppm—and sometimes even reach 1,500 ppm in poorly ventilated classrooms.
Common symptoms in children exposed to poor indoor air quality include:
Chronic fatigue and drowsiness in class. Frequent headaches, especially toward the end of the day. Irritation of the eyes, nose, and throat. Allergic rhinitis and more frequent asthma attacks.
These symptoms often disappear when the child goes outside or on weekends. This is a clear sign that the problem stems from the indoor environment, not from an isolated medical condition.
The Actual State of Indoor Air Quality in Montreal (Schools & Homes)
Montreal has made progress in recent years in monitoring air quality in schools. But the data show that there is still work to be done.
Data on Schools and Daycare Centers in Montreal
In 2023, the Quebec government invested $822 million to improve ventilation in schools. That’s good news. But the measures taken since then reveal the extent of the problem.
Tests conducted in Montreal public schools show a median CO₂ level of around 1,050 ppm in occupied classrooms. This is above the 1,000 ppm threshold recommended by Health Canada.
In early childhood centers (CPEs), the situation is even worse: 85 % of the facilities tested exceed 1,000 ppm of CO₂ during operating hours.
Schools that rely on natural ventilation—opening windows—have the worst results. In the winter, opening windows is impractical. Cold air comes in, heat escapes, and the children get cold. So the windows are closed, and CO₂ levels rise.
School buildings constructed before 1980—and there are many of them in Montreal—were never designed with mechanical ventilation systems. Classrooms, students, and computers were added, but the ventilation systems were not adapted accordingly.
The result? Children who spend 6 to 8 hours a day in spaces where the air isn't being refreshed quickly enough.
Indoor Air Quality at Home: A False Sense of Security
Many parents think the air at home is clean. After all, it's their home. They control what comes in.
A false sense of security.
Measurements taken in Montreal homes show an average concentration of fine particulate matter (PM2.5) of 8.9 µg/m³—nearly twice the threshold recommended by the World Health Organization (5 µg/m³).
In urban homes near major roads such as Avenue du Parc, Boulevard Métropolitain, or Rue Notre-Dame, concentrations can rise even higher due to automobile traffic.
In the United Kingdom, recent studies have measured PM2.5 levels of up to 20.2 µg/m³ in some homes. Montreal isn’t far behind, especially during periods of smoke from wildfires.
Sources of indoor pollution at home include:
Dust and allergens (dust mites, pet dander, pollen). Mold hidden in basements, behind furniture, or in poorly ventilated bathrooms. Volatile organic compounds (VOCs) from cleaning products, new furniture, and renovation materials. Cooking smoke, scented candles, and incense.
Without mechanical ventilation, these pollutants build up. They linger. And your children breathe them in day after day.
Indoor Pollution and Climate Change in Montreal
Climate change isn't just an external problem. It directly affects air quality in our homes and schools.
Forest Fire Smoke and Pediatric Asthma
The summer of 2023 will be remembered for a long time. For several weeks, Montreal was shrouded in a cloud of orange smoke from the wildfires in northern Quebec and Ontario.
The air quality index (AQI) has reached dangerous levels. People have been asked to stay indoors, close their windows, and limit outdoor activities.
But closing the windows isn't enough. Fine particles seep through cracks, window seals, and unfiltered ventilation systems.
A study by the University of Vermont published in 2025 shows that children exposed to wildfire smoke experience a significant increase in asthma attacks and emergency room visits for respiratory problems.
In Montreal, pediatric hospitals have confirmed a 30- to 40 % increase in asthma-related visits during periods of heavy smoke.
And this isn't an isolated incident. Scientists predict that these episodes of smog will become an annual occurrence due to climate change. Our children will grow up breathing this air.
Urban smog and cumulative exposure
In addition to wildfires, Montreal regularly experiences days of smog, especially in the summer when heat and humidity contribute to the formation of tropospheric ozone.
In 2025, Montreal recorded more than 20 days of poor air quality. For children living in the city, this cumulative exposure adds up year after year.
The problem is that even when the outdoor air is polluted, people think that staying indoors is enough. But without proper filtration and mechanical ventilation, indoor air quickly becomes just as polluted—if not more so—than outdoor air.
Children living in densely populated neighborhoods such as Villeray, Ahuntsic, or Rosemont are particularly at risk due to their proximity to major roads and heavy traffic.
Myths and Facts About Indoor Air Quality and Children
There are many myths circulating about indoor air quality. Some are true. Others are dangerous.
Common Myths in Montreal
«Indoor air is always safer than outdoor air»
No. Indoor air can be 2 to 5 times more polluted than outdoor air, especially in poorly ventilated homes. Pollutants accumulate and linger. Without air exchange, their concentration increases over time.
«A few days of smog or smoke is no big deal for a healthy child.»
False. Even brief exposure to fine particulate matter can trigger asthma attacks, irritate the airways, and affect lung function for weeks. For children with asthma or allergies, it’s even worse.
«Natural ventilation—opening the windows—is enough to keep the air clean.»
Not in Montreal. In the winter, opening windows causes heat loss and makes the room uncomfortable. In the summer, it lets in heat, allergens, and sometimes smoke from wildfires. Natural ventilation doesn’t filter anything. It doesn’t control humidity or temperature.
What the Scientific Data Show
The Quebec National Institute of Public Health (INSPQ) and Health Canada recommend controlled mechanical ventilation in all residential and school spaces.
Why? Because it’s the only way to ensure a constant supply of fresh, filtered air that meets the occupants’ needs.
Studies published in ScienceDirect confirm that schools equipped with mechanical ventilation systems featuring HEPA filters have lower CO₂ levels, fewer absences due to respiratory issues, and better cognitive performance among students.
It's not just a matter of comfort. It's a matter of health and development.
Warning Signs of Poor Indoor Air Quality
How can you tell if the air your children are breathing is clean? Here are the signs to look for.
At school or daycare
If your child regularly complains of headaches at the end of the school day, it’s often a sign that CO₂ levels are too high.
Excessive drowsiness in class, especially in the afternoon. Irritability or difficulty concentrating. Frequent colds or respiratory infections that seem to keep going around the class.
These symptoms often disappear on weekends or during vacations. If that’s the case, there’s a good chance the problem stems from the school environment.
You can ask the school if it monitors CO₂ levels in the classrooms. Since the Quebec government’s $822 million investment, several schools have installed sensors. But not all of them have done so yet.
At home
At home, the signs are sometimes more subtle.
Allergies that get worse indoors but improve outdoors. A persistent cough without a fever, especially at night or upon waking. Frequent condensation on windows in the winter—a sign that humidity is too high and the air isn’t circulating enough. A musty odor in certain rooms, even if it’s faint. Dust that accumulates quickly despite regular cleaning.
If you notice several of these signs, it's time to have the air quality in your home tested.
Practical Solutions for Improving Indoor Air Quality for Children
Improving indoor air quality is possible. And it doesn't always require major renovations.
Mechanical ventilation and air exchangers
The most effective way to ensure clean air at home is an air exchanger—also known as a heat recovery ventilator (HRV).
A VRC brings in fresh, filtered air from outside while expelling stale air from inside. It recovers between 60 % and 85 % of heat in the process, which prevents energy waste.
The result? You continuously refresh the air, filter out fine particles and allergens, and control humidity—all without opening the windows or driving up your heating bill.
According to Natural Resources Canada, approximately 25 % of homes in Quebec are equipped with an HRV. This number is increasing every year, especially in new construction and major renovations.
But many older homes—duplexes, triplexes, and century-old houses—still don't have mechanical ventilation. This is a problem, especially if you have children.
Installing a HRV costs between 2,500 $ and 5,000 $, depending on the size of your home and the complexity of the ductwork. It’s an investment that pays for itself through energy savings, fewer health problems, and greater daily comfort.
Cleaning Ventilation Systems
If you already have a ventilation system—central heating, air conditioning, or a heat recovery ventilation system—you should maintain it regularly.
Ventilation ducts accumulate dust, pet hair, mold spores, and sometimes even construction debris left behind during renovations.
When the system is running, it blows these contaminants directly into the air your children breathe.
Professional cleaning removes these buildup and immediately improves air quality. At Vortex Air, we use rotating brushes and HEPA vacuums, and we inspect the entire system with a camera to make sure nothing is left behind.
We recommend cleaning every 3 to 5 years for residential homes, and more often if you have pets, if someone in the family has allergies, or if you’ve just completed renovations.
Are you wondering if your ducts need to be cleaned? We offer a Free inspection to assess the air quality in your home. We measure, we inspect, and we give you the straight facts—no pressure, no charge.
Filtration, Humidity, and Best Daily Practices
In addition to ventilation, a few simple steps can make a big difference:
- Use air purifiers with HEPA filters in children's bedrooms, especially during episodes of smoke or smog. Air purifiers are not a substitute for ventilation, but they do provide an extra layer of protection.
- Keep the relative humidity between 30 % and 50 % in the winter, and between 40 % and 60 % in the summer. If it’s too dry, it irritates the respiratory tract. If it’s too humid, it promotes mold growth. A basic hygrometer costs 20 $ at a hardware store.
- Change the filters in your heating system every 3 months, and more often if you have pets. A clogged filter blocks airflow and reduces the system's efficiency.
- Avoid scented products — candles, air fresheners, and strongly scented laundry detergents. Many of these release volatile organic compounds (VOCs) that irritate children’s airways.
- Ventilate the room after activities that generate moisture : showering, cooking, doing laundry. Use the range hood and bathroom fan to vent moisture directly outside.
These small, everyday actions, combined with proper mechanical ventilation, create a much healthier environment for your children.
Regulatory Framework and Initiatives in Quebec
Quebec has taken significant steps in recent years to improve air quality in schools.
CO₂ Monitoring in Schools
In 2021, the Quebec government announced an investment of 822 million dollars to improve ventilation in schools and school service centers.
Some of this money is used to install CO₂ sensors in classrooms. These sensors measure CO₂ levels in real time and alert teachers when the level exceeds 1,000 ppm.
Some schools have also implemented digital systems that automatically adjust ventilation based on CO₂ readings. This is a significant step forward.
But not all schools have these systems yet. And in after-school care centers and private daycare centers, supervision is often nonexistent.
If you have children in school, don’t hesitate to ask the administration: Does the school monitor CO₂ levels? Are the ventilation systems maintained regularly?
Role of the INSPQ and Health Canada
The Quebec National Institute of Public Health (INSPQ) regularly publishes recommendations on indoor air quality. These recommendations establish clear thresholds:
CO₂: maximum 1,000 ppm in occupied spaces. Relative humidity: between 30 % and 50 % in winter. Fine particulate matter (PM2.5): maximum 10 µg/m³ over a 24-hour period (ideally below 5 µg/m³).
Health Canada also recommends installing mechanical ventilation in all residential spaces, especially in airtight homes built after 2000.
These recommendations are not legal requirements for private residences. However, they represent best practices based on decades of scientific research.
Following these recommendations means protecting your family's health.
Why Local Expertise Makes a Difference in Montreal
Improving indoor air quality in a Montreal home is different from anywhere else. Our buildings are unique. So is our climate.
Challenges Specific to Montreal Buildings
Montreal has thousands of duplexes, triplexes, and older homes built between 1900 and 1960. These buildings were never designed with mechanical ventilation systems.
Many are attached homes—they share walls with neighbors. This complicates the installation of ductwork and requires a customized approach.
Neighborhoods such as Villeray, Ahuntsic, and Plateau-Mont-Royal—as well as Laval and Longueuil on the North Shore and South Shore—each have their own architectural characteristics.
Not to mention the climate challenges: harsh winters with extreme temperature swings, humid summers, and now annual episodes of smoke from wildfires.
Installing a VRC in a century-old house in Rosemont is not the same as installing one in a new condo in Griffintown. It requires experience, creativity, and in-depth knowledge of local buildings.
A professional, compassionate, and preventive approach
At Vortex Air, we've been operating in Montreal for over 10 years. We understand the challenges of older homes, duplexes, and converted condos.
Our approach is simple: we always start with a free inspection. We measure air quality, assess humidity levels, and inspect existing systems.
Next, we’ll explain what’s really going on. We’ll offer solutions tailored to your situation—never any high-pressure sales, never any one-size-fits-all solutions that don’t work.
We are INVC-certified and in the process of obtaining NADCA certification—the two leading standards for ventilation and duct cleaning in North America. More than 500 Montreal families trust us to protect their health and that of their children.
We’re open 7 days a week, from 7 a.m. to 9 p.m. We answer the phone 24/7 at 514-214-7492. And we treat you with the same respect and honesty we’d want for our own family.
Are you concerned about the quality of the air your children breathe at home? Call us at 514-214-7492, visit vortexair.ca, or email us at info@vortexair.ca to talk to a local air quality expert. We'll help you understand what's going on and find practical solutions.
FAQ – Children's Health and Indoor Air Quality in Montreal
What CO₂ level is safe for children?
Health Canada recommends keeping CO₂ levels below 1,000 ppm in occupied spaces. For children’s bedrooms, aim for a level between 600 and 800 ppm. Above 1,000 ppm, sleep quality begins to decline.
Do air purifiers replace ventilation?
No. Air purifiers filter out particles and certain pollutants, but they do not circulate fresh air. They do not reduce CO₂ or humidity. An air purifier is a useful addition, especially during periods of smoke, but it is never a substitute for adequate mechanical ventilation.
How often should you clean your ventilation ducts?
Every 3 to 5 years for a residential home. More often if you have pets, if someone has severe allergies, or after major renovations. Professional cleaning removes accumulated allergens and immediately improves air quality.
Is dry air dangerous for children?
Yes. Air that is too dry (below 30 % relative humidity) irritates the respiratory tract, dries out the nasal mucous membranes, and makes children more vulnerable to respiratory infections. In the winter, use a humidifier to maintain humidity levels between 30 % and 40 %.
How can I tell if my child's school is well-ventilated?
Ask the administration whether the school monitors CO₂ levels in classrooms and whether the ventilation systems are maintained regularly. Since the government’s 822 million investment, several schools have installed sensors. If your child regularly complains of headaches or fatigue at school, this is a sign that warrants further investigation.
Do wildfires affect indoor air quality even when the windows are closed?
Yes. Fine particulate matter (PM2.5) enters through cracks, window seals, and unfiltered ventilation systems. Closing windows helps, but without HEPA filtration, indoor air eventually becomes almost as polluted as outdoor air during periods of heavy smoke.
Your children’s health starts with the air they breathe. At school, at home, while they sleep—every hour counts.
Indoor air quality isn’t a luxury. It’s a necessity. And in Montreal, with our harsh winters, our increasingly polluted summers, and our thousands of older homes, it’s a challenge we must take seriously.
If you have any doubts, questions, or concerns about the air your children are breathing, don’t wait. Have your home tested. Ask questions at school. Take concrete action.
At Vortex Air, we're here to help you. We take measurements, explain things, and offer solutions tailored to your family and your budget.
Call us at 514-214-7492, visit vortexair.ca, or email us at info@vortexair.ca. We offer free inspections, honest advice, and solutions that really work.
Because your children deserve to breathe clean air—at school and at home.
