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.

The Environmental Advantages of Building Green

Jennifer Crowley
Jul 28, 2023
3 min read

Updated: Jul 9, 2024

Tiered green glass office building surrounded by trees and even has greenery on the rooftop — Green building takes into account the life cycle of a building, including the impact of construction, operation, maintenance, and eventual demolition or recycling to minimize its impact on the environment..

As concerns about climate change and the environment continue to grow, more and more people are turning to sustainable building practices. One popular approach is green building, which seeks to minimize the environmental impact of construction and promote a healthier, more sustainable way of living. In this post, we will explore the concept of green building and its environmental benefits.

Defining Green Building

A Green building, also known as sustainable building or eco-building, refers to the practice of designing and constructing buildings in a way that minimizes their environmental impact. The environmental advantages of Green Building include everything from reducing energy and water consumption to using eco-friendly materials and promoting a healthier indoor environment. Green building also takes into account the life cycle of a building, including the impact of construction, operation, maintenance, and eventual demolition or recycling.

Green building is a holistic approach that looks at the entire building and its surroundings. For example, a green building might be designed to work harmoniously with the natural environment, incorporating elements like passive solar heating or natural ventilation. It might also prioritize using recycled or locally sourced materials, reducing transportation emissions and supporting the local economy.

Environmental Advantages of Building Green

Green building offers a wide range of environmental benefits. Here are some examples of the most significant advantages:

Reduced carbon footprint: Buildings significantly contribute to greenhouse gas emissions and climate change. Green buildings are designed to minimize this impact by reducing energy consumption and using renewable energy sources like solar or wind power. By doing so, they help to reduce the amount of greenhouse gas emitted into the atmosphere.
Conservation of natural resources: Traditional building practices often rely on non-renewable resources like virgin timber and fossil fuels. Green building prioritizes using sustainable materials, such as recycled steel, bamboo, and reclaimed wood. It also promotes using water-efficient fixtures, like low-flow toilets and showerheads, and reusing greywater. By reducing the demand for new resources and minimizing waste, green building helps to conserve natural resources and reduce the environmental impact of construction.
Improved indoor air quality: Traditional building materials often contain harmful chemicals and pollutants that can affect indoor air quality. On the other hand, green building emphasizes the use of non-toxic, low-emission materials, such as low-VOC paints, adhesives, and sealants. It also prioritizes ventilation and air filtration systems to promote a healthier indoor environment.
Energy efficiency: Green buildings are designed to use less energy, reducing fossil fuel demand and mitigating climate change’s effects. This can be achieved through various measures, such as using insulation and air sealing to reduce heat loss, installing energy-efficient HVAC filters, lighting and appliances, and utilizing renewable energy sources like solar or wind power.

Real-Life Examples

Green building is becoming increasingly common around the world. Here are some real-life examples of green buildings and their environmental benefits:

The Bullitt Center

Facade of the Bullit Center in Seattle Washington — The Bullit Centre's sustainable architecture aims to achieve net-zero in energy and water usage.

Seattle, United States

The Bullitt Center is a 6-story office building that is designed to be completely self-sustaining, generating its own electricity, collecting and filtering rainwater, and composting its own waste. It is also constructed with a range of eco-friendly materials, including Forest Stewardship Council-certified wood and low-VOC finishes.

The Pixel Building

Melbourne, Australia

The Pixel Building is a multi-use building powered entirely by renewable energy, with a 98-kilowatt solar array on the roof. It is also constructed with a range of sustainable materials, such as recycled content carpet tiles and low-VOC paints. The building is designed to be carbon-neutral over its lifetime, offsetting any carbon emissions produced during construction and operation.

The Edge

Amsterdam, Netherlands

The Edge is a futuristic office building designed to be one of the most sustainable buildings in the world. It features a range of innovative green technologies, including a smart lighting system that adjusts to the needs of individual employees and a rooftop solar array that provides all of the building’s electricity needs. The building is also designed to be highly energy-efficient, with triple-glazed windows and a high level of insulation.

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