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.

What are ESG Goals and Why Are They Important?

Jennifer Crowley
Aug 1, 2023
3 min read

Updated: Jul 8, 2024

Female hand outstretched amidst a blurred grennery backdrop and holding a graphic image depicting images of ESG including people, government, ecology, industrial building, windmills and the globe — Environmental, Social, and Governance, ESG has emerged as a robust framework that evaluates a company’s impact on the environment and society, as well as its governance practices.

In recent years, the business landscape has witnessed a significant shift towards sustainability and responsible practices. One of the key concepts at the forefront of this movement is ESG. Standing for Environmental, Social, and Governance, ESG has emerged as a robust framework that evaluates a company’s impact on the environment and society, as well as its governance practices. This blog post aims to provide an in-depth understanding of ESG goals, highlighting its importance in fostering sustainable and responsible business practices.

Understanding ESG

ESG refers to a set of criteria used to assess a company’s performance in three critical areas: environmental, social, and governance. Each component carries its significance and contributes to evaluating a company’s overall sustainability and responsible practices.

1. Environmental Factors

Environmental factors assess a company’s impact on the environment. This includes its carbon footprint, resource consumption, waste management, pollution levels, and commitment to renewable energy sources. ESG encourages companies to adopt eco-friendly practices, reduce emissions, conserve resources, and work towards mitigating climate change.

2. Social Factors

Social factors focus on a company’s relationships with its employees, customers, suppliers, and communities. It encompasses labour standards, employee welfare, diversity and inclusion, product safety, customer satisfaction, community engagement, and philanthropic activities. ESG emphasizes the importance of fair treatment, ethical behaviour, and positive social impact.

3. Governance Factors

Governance factors evaluate a company’s internal structure, leadership, and decision-making processes. It includes aspects such as board composition, executive compensation, transparency, accountability, and risk management. ESG promotes strong corporate governance, ethical leadership, and responsible decision-making to ensure long-term value creation and protection for all stakeholders.

The Importance of ESG

ESG has gained immense importance in today’s business landscape due to several reasons:

Risk Management

Adopting ESG practices helps companies identify and manage potential risks. By addressing environmental and social issues proactively, businesses can mitigate legal, reputational, and operational risks. Effective governance practices also reduce the likelihood of fraud and unethical behaviour, protecting the company’s reputation and financial stability.

2. Long-term Value Creation

ESG practices contribute to long-term value creation. By integrating sustainability into their business strategies, companies can identify opportunities for innovation, cost savings, and enhanced operational efficiency. Consumers, investors, and employees increasingly prefer companies that demonstrate a commitment to sustainable and responsible practices, leading to increased market competitiveness and profitability.

3. Stakeholder Engagement

ESG encourages companies to engage with their stakeholders, including employees, customers, investors, and communities. By actively involving stakeholders in decision-making processes and considering their perspectives, companies can build trust, loyalty, and stronger relationships. This fosters a positive corporate culture, attracts top talent, and enhances brand reputation.

4. Positive Environmental and Social Impact

Adopting ESG practices allows companies to make a positive impact on the environment and society. By reducing emissions, conserving resources, promoting social equality, and supporting local communities, businesses can contribute to a more sustainable and equitable world. This not only benefits the planet and society but also strengthens the company’s social license to operate.

ESG Score and Rating and What It Means For Businesses

Circular chart depicting the breakdown of ESG Scoring factors broken out by environmental, social and governance factors — To promote consistency and transparency in ESG reporting, several frameworks and standards have emerged.

ESG scores are determined by third-party firms that have their own methodologies to identify a company’s ESG rating. Currently, this isn’t a streamlined process across the board, and different companies have their own way of determining a company’s ESG rating. The rating help give an overall picture of the company’s performance in these three areas.

Typically, ESG scores are rated from 0 to 100, with anything above 70 classified as a “good” ESG rating, while anything below 50 is considered a “bad” rating. Some systems, however, rely on a letter-based scoring system where a grade of C is the worst, and A is the best.

ESG Goals; Frameworks and Standards

To promote consistency and transparency in ESG reporting, several frameworks and standards have emerged. These include the Global Reporting Initiative (GRI), the Sustainability Accounting Standards Board (SASB), and the Task Force on Climate-related Financial Disclosures (TCFD). Adopting these frameworks helps companies measure and communicate their ESG performance, enabling investors and stakeholders to make informed decisions.

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