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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

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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. PNASNature


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:

  1. Dilute what’s in the room (ventilation/outdoor air)

  2. Remove what’s in the room (filtration/air cleaning)

  3. 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+1Environmental 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.

Five Early Steps to Prepare for Your Carbon Report

  • Writer: Ava Montini
    Ava Montini
  • Jan 21
  • 4 min read

Preparing a carbon report is a powerful opportunity to align your organization with forward-thinking strategies, meet stakeholder expectations, and uncover new ways to enhance operational efficiency. As sustainability continues to shape the business landscape, reporting on carbon emissions has evolved beyond compliance to become a cornerstone of long-term value creation.


The reality is clear: over 66% of the world's largest companies now disclose climate-related data through frameworks like CDP, reflecting the growing demand for transparency. In the U.S., buildings alone account for approximately 31% of total greenhouse gas emissions, making industries like real estate and property management key players in addressing climate challenges.


While the process can seem complex, it is entirely manageable with the right approach. From understanding reporting frameworks to streamlining data collection, this journey is about building a clear, actionable plan that sets your organization up for success. By focusing on key priorities and leveraging proven strategies, you can take confident steps toward creating a carbon report that reflects your commitment to innovation and leadership.


Here's how to begin:

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1. Understand the Frameworks and Requirements

Carbon reporting begins with understanding the frameworks and regulations that apply to your organization. These frameworks are essentially the rulebooks that guide how you measure, calculate, and present emissions data. Choosing the right one depends on your industry, geographic location, and specific requirements from stakeholders, investors, or regulators.


For example, the Greenhouse Gas Protocol (GHGP) is a foundational standard that categorizes emissions into three scopes: Scope 1 (direct emissions), Scope 2 (indirect emissions from purchased energy), and Scope 3 (all other indirect emissions across your value chain). Meanwhile, platforms like CDP and frameworks like TCFD focus on how companies disclose emissions to investors and other audiences.


The first step is identifying which frameworks are required or preferred for your organization. U.S.-based companies should pay particular attention to the SEC’s proposed rules for climate disclosures, which could require public companies to report more detailed emissions data. Additionally, consulting with sustainability professionals or using resources like the Greenhouse Gas Protocol’s Corporate Standard can provide clarity and structure.



Scopes 1, 2 and 3 Emissions Inventorying and Guidance | US EPA
Scopes 1, 2 and 3 Emissions Inventorying and Guidance | US EPA

2. Build a Comprehensive Emissions Inventory

Your emissions inventory is the foundation of your carbon report. It involves identifying and quantifying all emissions across your organization. This inventory will include direct emissions from owned assets, indirect emissions from energy use, and, if applicable, emissions from your value chain.


To start, define your organizational boundaries. Will you report emissions based on operational control (activities you oversee directly) or equity share (based on your ownership percentage)? Next, gather data from utility bills, fuel logs, procurement records, and any other relevant sources. If collecting this data feels overwhelming, prioritize high-impact emissions sources first, such as energy use or transportation, and expand from there.


Digital tools can simplify this process. Platforms like EPA’s Simplified GHG Emissions Calculator or specialized carbon accounting software can help centralize and automate data collection. Partnering with teams across your organization—such as facilities management and procurement—can also ensure data is accurate and complete.


Other Resources to Leverage:



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3. Focus on High-Impact Emissions Sources

Not all emissions are equally significant, and prioritizing high-impact areas can make your efforts more effective. By focusing on emissions sources that account for the largest share of your footprint or are most relevant to stakeholders, you can direct resources where they’ll have the greatest impact.


To prioritize effectively, consider conducting a materiality assessment. This process involves evaluating which emissions sources are most relevant to your business and stakeholders. Engaging with investors, clients, and regulators can provide additional insights into what matters most. Benchmarking your data against industry peers can also help you identify areas where your organization may be lagging or leading.


Visualizing emissions through heatmaps or similar tools can further clarify where to focus your efforts. These insights can guide decisions on upgrades, retrofits, or supply chain adjustments, ensuring your carbon reporting efforts translate into meaningful action.


Resources to Leverage:



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4. Set Clear Reduction Targets and Timelines

Once you have a clear picture of your emissions, the next step is setting reduction targets that align with your organizational goals. These targets provide direction and accountability, signalling to stakeholders that you’re serious about sustainability.


Begin by establishing a baseline year—a starting point against which future progress will be measured. From there, set short- and long-term goals. For example, you might aim to reduce Scope 2 emissions by 25% over five years through renewable energy procurement or energy efficiency upgrades. Aligning your targets with global initiatives like the Science-Based Targets Initiative (SBTi) can further demonstrate your commitment to climate goals.


Regularly communicating progress toward these goals can help build trust with investors, tenants, and other stakeholders. Transparency about challenges and adjustments also demonstrates your commitment to continuous improvement.


Resources to Leverage:



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5. Invest in Infrastructure and Expertise

Successful carbon reporting requires robust infrastructure and a knowledgeable team. Whether it’s tools for data collection or employee training, these investments can streamline the process and ensure accuracy.


Many companies start by adopting carbon accounting software, which automates data management and reporting. Platforms like Sphera, Envizi, or Ecovadis offer features that track emissions across scopes, analyze trends, and generate reports tailored to specific frameworks. For organizations with complex operations, these tools can save significant time and effort.


Equipping your team with the right expertise is equally important. Training employees on reporting frameworks, data collection methodologies, and compliance requirements can reduce reliance on external consultants over time. Partnering with third-party verification bodies can also enhance the credibility of your reports, especially if they’ll be shared with investors or regulators.


Resources to Leverage:


Preparing for your carbon report is about more than compliance—it’s a strategic opportunity to lead on sustainability, improve operations, and strengthen stakeholder relationships. While the process may seem complex, following these five steps will provide a clear roadmap to get started.


As you embark on this journey, remember that every organization’s path will look a little different. What matters most is taking the first step and building momentum. By investing in education, planning, and collaboration, you can turn the challenge of carbon reporting into an opportunity to create lasting value for your business and the environment.

Explore expert insights, stay up to date with industry events, and gain a deeper understanding of the cutting-edge developments that are revolutionizing the indoor air quality landscape within Blade Air's comprehensive Insights Hub.

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