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.

Achieving Green Building Standards Certifications with Superior Indoor Air Quality (IAQ) Practices

Jennifer Crowley
Mar 11, 2024
3 min read

Updated: Jul 8, 2024

Industrial Worker duo checking IAQ meaurements — Transparent reporting of IAQ data enables building managers to make data-driven decisions and implement targeted interventions to improve indoor air quality over time.

Welcome to Blade's latest blog post, where we explore the critical intersection of Indoor Air Quality (IAQ) and green building standards. As leaders in air quality solutions, we understand the importance of creating sustainable and healthy indoor environments. In this comprehensive review, we'll delve into how compliance with advanced green building standards, such as the WELL Building Standard and RESET, can significantly enhance IAQ in commercial spaces.

Understanding Green Building Standards:

Green building standards aim to promote sustainability, energy efficiency, and occupant well-being in the built environment. They encompass a range of criteria related to building design, construction, operation, and maintenance. While traditional green building standards focus primarily on energy efficiency and environmental impact, advanced standards like WELL and RESET prioritize occupant health and comfort, including IAQ.

The WELL Building Standard:

The WELL Building Standard is a performance-based certification system that focuses on enhancing human health and well-being through the built environment. It addresses seven core concepts, including air, water, nourishment, light, fitness, comfort, and mind. Within the air concept, WELL places a strong emphasis on IAQ by setting stringent requirements for indoor air quality parameters, ventilation, filtration, and pollutant control measures.

Compliance with the WELL Standard involves implementing strategies to minimize indoor air pollutants, enhance ventilation systems, and promote IAQ monitoring and maintenance practices. By achieving WELL certification, commercial buildings can demonstrate their commitment to providing healthy indoor environments for occupants, leading to improved employee productivity, satisfaction, and overall well-being.

The RESET Standard:

RESET is a building certification program focused specifically on indoor air quality monitoring and management. It utilizes real-time monitoring technology to continuously track key IAQ parameters, including particulate matter, volatile organic compounds (VOCs), carbon dioxide (CO2), temperature, and humidity. RESET certification requires adherence to strict IAQ performance criteria and the implementation of proactive measures to maintain healthy indoor air.

By integrating real-time IAQ monitoring systems, commercial buildings can effectively identify IAQ issues, optimize ventilation strategies, and ensure compliance with RESET standards. The transparent reporting of IAQ data enables building managers to make data-driven decisions and implement targeted interventions to improve indoor air quality over time.

The Benefits of Green Building Standards for IAQ:

Compliance with advanced green building standards offers numerous benefits for IAQ in commercial spaces, including:

Improved Occupant Health and Comfort: By prioritizing IAQ, green building standards create healthier and more comfortable indoor environments for occupants, reducing the risk of respiratory problems, allergies, and other health issues.
Enhanced Productivity and Performance: Good IAQ has been shown to positively impact employee productivity, morale, and cognitive function. By investing in IAQ improvements, businesses can boost overall performance and competitiveness.
·Regulatory Compliance and Recognition: Achieving certification under green building standards demonstrates a commitment to sustainability and occupant well-being, enhancing the reputation and marketability of commercial properties.

The intersection of Indoor Air Quality (IAQ) and green building standards represents a significant opportunity for enhancing occupant health, comfort, and sustainability in commercial spaces. Compliance with advanced standards such as the WELL Building Standard and RESET enables businesses to create healthier indoor environments, improve IAQ performance, and reap numerous benefits, including enhanced occupant well-being and productivity.

At Blade, we're committed to supporting businesses in achieving their IAQ and sustainability goals through innovative solutions and expertise. Contact us today to learn more about how we can help your commercial property meet and exceed green building standards while prioritizing IAQ excellence.

Insights Hub

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor

Lorem ipsum dolor sit amet cotetur

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor

Lorem ipsum dolor sit amet cotetur

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor

Lorem ipsum dolor sit amet cotetur