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.

How Eco-Friendly Buildings Foster Sustainable Living

Jennifer Crowley
Aug 1, 2023
3 min read

Updated: Jul 8, 2024

High rise building with lush greenery filled balconies aside a low-rise building, the face of which is covered in greenery — An environmentally sustainable building is a structure that minimizes resource consumption, reduces emissions, and manages waste more efficiently.

In today’s rapidly changing world, the need for sustainable practices has become more critical than ever. As we strive to mitigate the impacts of climate change, eco-friendly buildings have emerged as a crucial solution. These structures, designed with sustainable materials and energy-efficient systems, not only reduce their environmental footprint but also offer numerous benefits to occupants and the surrounding community. This blog will explore how eco-friendly buildings contribute to a greener future and foster sustainable living.

What are Eco-Friendly Buildings?

An environmentally sustainable building is a structure that minimizes resource consumption, reduces emissions, and manages waste more efficiently. Certain green buildings even positively influence the surrounding environment, playing a role in enhancing the global climate. Additionally, eco-friendly buildings are purposefully designed to benefit the individuals who occupy them. Through features such as enhanced ventilation, insulation, and utilization of natural light, these buildings positively impact occupants’ well-being, leading to improved health, productivity, and overall quality of life.

Energy Efficiency

One of the primary features of eco-friendly buildings is their focus on energy efficiency. Through careful design, insulation, and use of renewable energy sources, these buildings significantly reduce energy consumption. By incorporating features such as solar panels, efficient lighting systems, and well-insulated walls, they minimize the need for fossil fuel-based energy, resulting in lower greenhouse gas emissions and reduced strain on the grid.

Water Conservation

Eco-friendly buildings employ innovative strategies for water conservation. To minimize water wastage, they integrate water-saving fixtures like low-flow toilets, faucets, and shower heads. Additionally, rainwater harvesting systems are often incorporated to collect and reuse rainwater for irrigation or non-potable purposes. These practices help reduce water consumption, relieve stress on local water supplies, and promote sustainable water management.

Sustainable Materials

The choice of materials used in construction plays a significant role in the eco-friendliness of a building. Sustainable buildings prioritize the use of renewable, recycled, and locally sourced materials. For instance, incorporating bamboo, reclaimed wood, or recycled metal helps reduce the demand for virgin materials and decreases the carbon footprint associated with production and transportation. By opting for environmentally friendly materials, these buildings conserve natural resources and promote a circular economy.

Indoor Air Quality (IAQ)

Eco-friendly buildings prioritize the health and well-being of occupants by maintaining excellent indoor air quality. By using low-VOC (volatile organic compounds) paints, adhesives, and building materials, they minimize the release of harmful chemicals into the air. Moreover, adequate ventilation systems and efficient air filtration technologies help remove pollutants, allergens, and contaminants, creating a healthier living and working environment.

Sustainable Landscaping

Eco-friendly buildings extend their sustainability efforts beyond their physical structures. They incorporate sustainable landscaping practices that enhance biodiversity and reduce the environmental impact of outdoor spaces. This includes utilizing native plants, installing efficient irrigation systems, creating green roofs and walls, and implementing permeable surfaces to reduce stormwater runoff. These measures contribute to improved air quality, reduced heat island effect, and harmonious integration of buildings with the natural environment.

Enhanced Quality of Life

Living or working in an eco-friendly building offers several benefits to occupants. With improved indoor air quality, ample natural light, and reduced exposure to harmful chemicals, occupants often experience enhanced comfort, productivity, and overall well-being. Moreover, energy-efficient systems contribute to lower utility bills, making eco-friendly buildings more cost-effective in the long run. By prioritizing sustainable living, these buildings foster a sense of responsibility and environmental stewardship among occupants.

Green or sustainable buildings are designed to be eco-friendly and can include any number of the features above.

The Goal of Eco-Friendly Buildings

There are specific goals to keep in mind when designing an eco-friendly building, some of which include:

Optimized resource utilization
Integration of resource recycling infrastructure
Implementation of efficient waste management practices
Fostering human health, well-being, and productivity
Mitigation of carbon emissions and air pollution impacts
Environmental friendliness throughout the building’s life cycle, including materials recovery during demolition
Lower operational and maintenance expenses
Flexibility for multi-use and adaptability to different purposes over time
Incorporation of aesthetically pleasing design that enhances the surrounding area
Utilization of sustainable materials and techniques throughout the building’s lifespan

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