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 Role of ESG in Building IAQ Retrofits: Achieving Sustainability Goals

Jennifer Crowley
Jul 4, 2024
4 min read

Updated: Jul 8, 2024

Diverse team, middle-aged Asian businessman, Caucasian young businesswoman, Muslim hijab-wearing focused in ESG goals — Retrofitting buildings to optimize indoor air quality (IAQ) offers substantial environmental, Social and Governance benefits.

Environmental, Social, and Governance (ESG) criteria are becoming increasingly crucial in the corporate world. These principles guide companies in making decisions that are not only financially beneficial but also environmentally sustainable, socially responsible, and compliant with governance standards.

As businesses strive to meet these goals, building retrofits emerge as a key strategy. Retrofitting buildings with advanced indoor air quality solutions from Blade Air can significantly contribute to achieving ESG objectives, enhancing sustainability, and promoting occupant health.

Environmental Impact

Clear glass light bulb protruding from the soil and surrounded by greenery — HVAC systems can be energy-intensive, contributing to higher greenhouse gas emissions.

One of the primary components of ESG in building IAQ retrofits is the environmental impact of business operations. Retrofitting buildings to optimize IAQ with Blade Airs solutions offers substantial environmental benefits:

Energy Efficiency: According to the U.S. Department of Energy, HVAC systems account for about 40% of the energy used in commercial buildings. Blade Air’s advanced filtration systems, such as our Pro Filters and HEPA+ filters, enhance the efficiency of HVAC systems. By reducing the load on these systems, energy consumption is significantly lowered. This not only reduces operational costs but also minimizes your building’s carbon footprint.

Carbon Footprint Reduction: The U.S. Environmental Protection Agency (EPA) estimates that improving energy efficiency in buildings can reduce greenhouse gas emissions by up to 20%. Traditional HVAC systems can be energy-intensive, contributing to higher greenhouse gas emissions. Blade Air’s solutions, including UV-C light technology and zero-waste carbon filters, help optimize HVAC performance, leading to lower emissions and a more sustainable operation.

Resource Conservation: By improving the longevity and efficiency of existing HVAC systems, Blade Air’s IAQ retrofitting solutions reduce the need for frequent replacements and repairs, conserving resources and reducing waste.

Social Responsibility

Man's hands with arms outstretched, holding a small globe representing the earth — Enhanced IAQ reduces the presence of allergens, pollutants, and pathogens.

The social aspect of ESG focuses on the impact of business operations on people and communities. Improving IAQ through retrofitting has significant social benefits:

Occupant Health: The World Health Organization (WHO) states that poor indoor air quality is responsible for approximately 3.8 million deaths annually due to non-communicable diseases like stroke and chronic respiratory diseases. Enhanced air quality reduces the presence of allergens, pollutants, and pathogens in indoor environments. This leads to fewer respiratory issues, allergies, and illnesses among occupants, promoting overall health and well-being.

Community Wellbeing: Healthier indoor environments contribute to the well-being of the community. Schools, offices, and residential buildings that prioritize air quality create safer, more comfortable spaces for people to live, work, and learn.

Employee Productivity: A Study by the Harvard T.H. Chan School of Public Health has shown that improving IAQ can boost productivity by up to 11%. Better air quality is linked to improved cognitive function and by investing in air quality improvements, businesses can foster a healthier, more productive workforce.

Governance and Compliance

ESG environment social governance investment concept. Business people meeting,Plan strategies future — By choosing sustainable retrofitting solutions, businesses align their operations with ethical practices.

Governance in ESG involves adherence to regulations and standards that promote sustainability and ethical practices. Retrofitting buildings for IAQ with Blade Air solutions ensures compliance with these regulations:

Regulatory Compliance: Many regions have stringent air quality standards and energy efficiency regulations. For example, the EPA’s Clean Air Act requires businesses to meet specific air quality standards to protect public health. Blade Air’s advanced filtration and purification systems help buildings meet and exceed these standards, avoiding potential fines and legal issues.

Sustainability Reporting: Companies increasingly need to report on their sustainability efforts. Implementing Blade Air’s solutions provides tangible improvements in energy efficiency and air quality, which can be documented and reported to stakeholders, demonstrating a commitment to ESG principles.

Ethical Practices: By choosing sustainable retrofitting solutions, businesses align their operations with ethical practices that prioritize the health of the environment and the community.

ESG in Building IAQ Retrofits Case Study

The Historic Toronto Distillery District

Gooderham & Worts building in Toronto's historic Distillery District — By implementing Blade Air's advanced air quality solutions, the Distillery District not only met but exceeded its ESG goals, setting a new standard for environmental sustainability and occupant well-being.

In December 2021, the Distillery District management team contacted Blade Air to improve IAQ in their buildings, which were currently running MERV-13 filters. They sought a solution that balanced reducing their carbon footprint with creating a healthier workspace for tenants, without the prohibitive costs of retrofitting and HEPA or UV solutions, which are energy-intensive.

Blade Air implemented electromagnetic Pro Filters, which use active polarization fields to outperform HEPA in capturing particulate matter in the viral range. These filters have nearly 90% lower static pressure than HEPA and over 70% lower than MERV-13 filters, leading to significant energy savings. Additionally, electromagnetic filters inactivate viruses, offering comprehensive air quality improvement.

ESG Results:

Energy Savings: Achieved an impressive 75% reduction in fan motor energy consumption, significantly lowering operational costs and environmental impact.
Superior Indoor Air Quality: Blade Air's electromagnetic Pro Filters outperformed previous MERV-13 filters by 2.25 times in capturing and removing airborne bacteria, vastly improving air quality.
Streamlined Maintenance: By switching to Pro Filters, which only need to be replaced twice a year instead of quarterly, the Distillery District saw up to a 50% reduction in labor costs associated with maintenance.
Logistical Savings: Pro Filters streamlined logistics by reducing storage and delivery needs, leading to an incredible 92% cost savings and further lowering emissions.

These outstanding results highlight Blade Air’s ability to drive substantial energy and operational savings, enhance cognitive function through superior air quality, and significantly reduce maintenance and logistical costs. By implementing Blade Air's advanced air quality solutions, the Distillery District not only met but exceeded its ESG goals, setting a new standard for environmental sustainability and occupant well-being.

Improving IAQ by integrating ESG principles into business operations is not only a strategic move but also a moral imperative in today’s world. Retrofitting buildings with Blade Air’s advanced air quality solutions helps businesses achieve their sustainability goals by improving energy efficiency, reducing carbon footprints, enhancing occupant health, and ensuring compliance with regulations.

Ready to integrate ESG principles into your building’s operations? Contact Blade Air today to discover how our advanced air quality solutions can help you achieve your sustainability goals. Transform your building, enhance occupant health, and demonstrate your commitment to the environment and community with your trusted Partners at Blade Air - Let’s make a positive difference, together.

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