Flu Season Meets School Season: How Smarter Air Quality Keeps Classrooms Healthy

Every fall, classrooms fill with students—and viruses. Discover how smarter air quality strategies like low-resistance filtration, ventilation, and HEPA keep schools healthier, reduce absences, and support better learning outcomes.

Ava Montini

Aug 19, 2025

Written by

Published on

The scene every September

Every September, the school bell rings and hallways come alive again. But as backpacks and lunch boxes make their way back into classrooms, another unwelcome guest tends to sneak in too: flu season.

Teachers know it all too well. The cough that spreads from desk to desk, the hand sanitizer bottles running low by mid-morning, the spike in absenteeism that leaves lesson plans hanging. Parents know it when the inevitable call from the school office comes: “Your child has a fever, please come pick them up.”

It’s a cycle we’ve come to accept as part of the school year. But what if healthier air could help change that story?

Why flu season and school season collide

Respiratory viruses (including influenza) spread more readily indoors, where exhaled particles accumulate. That’s not speculative; CDC/NIOSH is unambiguous that better indoor ventilation reduces occupants’ overall exposure to airborne viruses. CDC

We also know influenza isn’t only about big droplets from a sneeze. People exhale infectious virus in fine aerosols during normal breathing and speaking, which can linger and travel within a room. That was demonstrated in a landmark study that detected infectious influenza virus in exhaled breath from symptomatic adults, no cough required. PNAS Nature

The drier, colder air from the fall and winter cause low humidity, helping influenza survive and transmit more efficiently. Put simply: when we bring students back into dry, tightly sealed buildings, small airborne particles build up and stay infectious longer. That’s the fixable part.

Think of clean classroom air as a budget with three line items:

Dilute what’s in the room (ventilation/outdoor air)
Remove what’s in the room (filtration/air cleaning)
Disable what’s in the room (UVGI where appropriate)

The key is using them together, sized to the space, and tuned to the school day.

What the standards now say and why it matters

Before the pandemic, most schools designed ventilation systems mainly for comfort—things like controlling odours or keeping CO₂ levels down—not for stopping the spread of illness.

That changed with ASHRAE’s new Standard 241, which focuses specifically on infection control. ASHRAE’s Standard 241: Control of Infectious Aerosols changes the target by introducing Equivalent Clean Airflow (ECA)—a flexible, additive way to hit a per-person clean air goal using any combination of ventilation, filtration, and proven air cleaning. That means a classroom can meet its target by mixing outdoor air with high-efficiency filters, HEPA units, and/or UVGI, rather than relying on outdoor air alone. ASHRAE+1

In parallel, CDC/NIOSH and EPA emphasize practical steps for schools: keep systems maintained, upgrade to MERV-13 or better where equipment allows, and supplement with portable HEPA when central systems can’t carry the whole load. CDC+1 Environmental Protection Agency

The evidence that this keeps kids in class

In a study of 162 California elementary school classrooms, illness-related absences dropped by 1.6% for every extra 1 l/s‑person of ventilation. Increasing ventilation to meet the state standard (7.1 l/s‑person) from the average (4 l/s‑person) could reduce absences by 3.4%, gain $33 million annually in attendance-based funding, while costing just $4 million more in energy.
A study across Washington and Idaho found that a 1,000 ppm increase in indoor CO₂ correlated with a 0.5–0.9% drop in average daily attendance, translating into a 10–20% rise in student absences.
In controlled environments, each 500 ppm rise in CO₂ resulted in 1.4–1.8% slower response times, along with a 2.1–2.4% lower throughput on cognitive tasks.
Harvard’s COGfx study revealed that building occupants in green-certified, well-ventilated environments scored, on average, 101% higher in cognitive tests than those in conventional buildings.

“Will MERV-13 break my units?” (The energy/airflow reality)

The honest answer: it depends on the filter you pick and your fan capacity. Research on rooftop units shows that moving from MERV-8 to MERV-13/14 can raise cooling-mode energy use by a few percent if the filter adds a lot of resistance, or it can reduce airflow if the fan can’t keep up. That’s why filter selection matters as much as efficiency.

Not all MERV-13 filters are created equal. Traditional pleated designs often create a higher pressure drop, forcing HVAC systems to work harder and sometimes leading to performance issues. But newer filtration technologies (explicitly engineered for low resistance at high efficiency, like Blade Air's Pro Filter,) are changing that equation. By combining advanced media with optimized form factors, these filters deliver MERV-13 (and higher) performance without the heavy airflow penalty.

California’s Title 24 research reinforces this point: Many modern low-pressure MERV-13 options can maintain pressure drops under 0.20 in. w.c., keeping systems within safe operating ranges. That means schools can improve air quality, meet public health guidance, and stay compliant without sacrificing system efficiency or longevity.

When you factor in the bigger picture—fewer student absences, better cognitive performance, and improved overall school operations—the ROI clearly tilts toward upgrading. Healthier air doesn’t just protect occupants; it protects the bottom line.

How this translates into a classroom target (the ECA idea)

ASHRAE 241’s Equivalent Clean Airflow lets you add up all the ways you’re cleaning air—outdoor air, central filtration, HEPA, UVGI—until you reach the per-occupant target for your space type. It’s flexible, measurable, and avoids unrealistic demands for 100% outdoor air in cold snaps. ASHRAE

A practical approach:

Estimate your current outdoor air (from design or testing).
Add the “clean air” from MERV-13 upgrades (using published efficiencies) and from each HEPA unit’s clean air delivery rate.
If the sum doesn’t meet the ECA target, add another portable unit or rethink your filtration strategy. ASHRAE

What about measurement and transparency?

CO₂ for ventilation

Track a few representative rooms across grade levels and building wings. Persistently high readings during class point to areas needing a fix (dampers, schedules, or supplemental air cleaning). Health Canada’s 1000 ppm residential benchmark is a useful anchor for conversations with families and staff. Canada.ca

PM₂.₅ for smoke days

A couple of low-drift sensors at kid-height in hallways or problem rooms can confirm your filtration strategy keeps indoor levels below outdoors during wildfire events. Health Canada and EPA both recommend this principle. Canada.ca

Bottom line

Flu season doesn’t have to mean higher absence rates and strained HVAC systems. The most effective path is a consistent program: keep ventilation tuned, use filters that balance efficiency with low resistance, and supplement with portable HEPA or UVGI where it makes sense.

Breathe Easy: The Essential Guide to Navigating IAQ Business Regulations in Canada

Jennifer Crowley
Mar 4, 2024
3 min read

Updated: Jul 8, 2024

Building Facilities Manager Reviewing Site Compliance Checklist — Regular monitoring of IAQ parameters ensures ongoing adherence to standards.

Welcome, Canadian business leaders! Let's delve into a crucial yet often overlooked aspect of workplace health: indoor air quality (IAQ). The quality of the air we breathe during our workday significantly influences our well-being and productivity. In fact, A Canadian study revealed that nearly one-third of employee sick days are due to symptoms worsened by poor indoor air quality (IAQ). Similarly, a Massachusetts study saw a 35% reduction in sick leave in offices with good IAQ, saving businesses approximately $400 per employee annually. Imagine the impact of saving $400 per employee on your yearly budget.

Fortunately, Canada has robust IAQ regulations to ensure that our indoor environments promote health and safety. However, understanding, achieving, and maintaining compliance with these regulations can be intricate. Fear not! In this comprehensive guide, we will provide you with detailed insights and practical guidance on navigating IAQ regulations and standards in Canada, empowering you to keep your business compliant while prioritizing the health and comfort of your team.

Understanding IAQ Regulations and Standards:

To begin, let's grasp the fundamentals:

Image of textbooks with the title Rules & regulations

1. Health Canada sets forth comprehensive guidelines for IAQ, encompassing parameters such as temperature, humidity, ventilation, and air contaminants. These guidelines serve as the cornerstone for maintaining optimal IAQ in your workplace. If you are not familiar with them, please click the link above to learn more.

2. Many Canadian provinces also impose their own specific IAQ regulations, necessitating familiarity with local requirements. The chart below provides support in locating your Provincial regulations:

Chart outlining Provincial IAQ legislation guidance — Provincial IAQ Requirement Overview

3. Building codes also dictate ventilation systems, air filtration standards, moisture control measures, radon mitigation and the types of construction materials used to uphold IAQ standards in commercial spaces.

Achieving Compliance:

Now, let's strategize.

1. Initiating an IAQ assessment is paramount.

This assessment involves a thorough examination of your indoor air quality to identify potential issues and inform your mitigation plan. Depending on the size, age, and structure of the building, your IAQ audit may include air sample collection, a mould and moisture assessment, HVAC System evaluation and even an occupant survey. Consider engaging professional IAQ consultants for comprehensive and accurate results.

2. Ensure that your ventilation system operates efficiently.

Adequate airflow is crucial for circulating clean air throughout your workspace. Building codes typically specify minimum ventilation rates for various types of spaces within commercial buildings. These rates ensure adequate airflow to dilute indoor air pollutants and maintain acceptable IAQ levels. For example, the National Building Code of Canada (NBC) outlines ventilation requirements based on occupancy type, building size, and specific activities conducted within the space. Implementing a rigorous maintenance schedule and investing in high-quality air filters are key measures to mitigate pollutants effectively.

3. Adopting practices to minimize indoor pollutants, such as utilizing low-emission materials, prohibiting smoking, restricting the use of volatile organic compound emitting products and implementing stringent cleaning protocols, further enhances IAQ.

Furthermore, ensuring HVAC systems are regularly maintained, utilizing high efficiency air filters, and leveraging demand-controlled ventilation systems that adjust airflow based on occupancy levels and indoor air quality parameters all help to keep pollutants at compliant levels.

Maintaining Compliance:

Once your IAQ protocols are in place, maintaining compliance becomes imperative:

1. Regular monitoring of IAQ parameters ensures ongoing adherence to standards. Establish a systematic schedule for assessing air quality and promptly address any deviations from prescribed norms.

2. Equally vital is the implementation of a robust maintenance regimen. Regular servicing of HVAC systems and diligent upkeep of building infrastructure are essential to preserve optimal IAQ conditions.

3. Additionally, staying abreast of changes in IAQ regulations is crucial. Continuously monitor industry updates and engage with regulatory agencies to remain informed about evolving compliance requirements.

Navigating IAQ regulations may initially appear daunting, but armed with the right knowledge and approach, you can ensure a healthy indoor environment for your business. By comprehending the regulations, implementing effective strategies, and prioritizing maintenance, you not only meet legal requirements but also cultivate a workplace that promotes well-being and productivity. Remember, investing in IAQ compliance is an investment in the health and success of your business. Keep breathing easy, knowing that you're making a positive impact on your team and your bottom line.

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