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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.

Carbon Neutral vs Net Zero – What’s the Difference?

  • Writer: Jennifer Crowley
    Jennifer Crowley
  • Jul 28, 2023
  • 4 min read

Updated: Jul 9, 2024

Wodden cube cloks with various sustainability imaged stamped in green on the face of each, stacked into a pyramid
Carbon neutrality achieves a balance between carbon emissions and carbon offsets, while net zero aims to completely eliminate carbon emissions by generating renewable energy on-site.

Buildings play a critical role in our daily lives, providing us with shelter, workspaces, and places to gather. However, they also significantly impact the environment, accounting for a staggering 40% of global energy consumption and 33% of greenhouse gas emissions.


With the impacts of climate change becoming increasingly severe, it’s more important than ever to transition to green energy sources and green building practices. This is where the concepts of carbon neutrality vs net zero emissions come in. By achieving these goals, we can significantly reduce the carbon footprint of our buildings, contributing to a more sustainable future for all.


In this blog, we will dive deep into the world of carbon neutrality and net zero emissions, exploring the benefits, strategies, and challenges of achieving these goals in buildings. Join us on this journey as we discover how efficient HVAC systems can play a critical role in achieving carbon neutrality and net zero emissions in buildings.


Carbon Neutral Buildings

Illustrated chart showasing the balance of energy usage in a carbon neutral building vs typical building energy usage patterns
Carbon neutrality involves reducing energy consumption through energy efficiency measures.

A carbon-neutral building is one that has achieved net zero carbon emissions by balancing the amount of carbon emissions it produces with the amount of carbon it offsets or sequesters.


Achieving carbon neutrality typically involves reducing energy consumption through energy efficiency measures and using renewable energy sources to power the building.


Benefits of Carbon Neutral Buildings:

  1. Reduced carbon emissions and environmental impact

  2. Lower energy costs

  3. Improved indoor air quality and occupant comfort

  4. Enhanced building value and reputation


Net Zero Buildings

A net zero building is one that produces as much renewable energy on-site as it consumes over the course of a year. This means that the building produces zero net carbon emissions from energy consumption.


Benefits of Net Zero Buildings:

  1. Completely eliminates carbon emissions from energy consumption

  2. Lower energy costs

  3. Improved indoor air quality and occupant comfort

  4. Enhanced building value and reputation


Carbon Neutral vs. Net Zero: What is the Difference?

Carbon neutrality and net zero are two important concepts in the context of reducing carbon emissions and mitigating climate change, especially in the building sector. But what is the main difference between the two terms?

While both carbon-neutral and net-zero buildings aim to reduce carbon emissions and promote sustainable energy practices, the main difference lies in the approach.


Carbon neutrality achieves a balance between carbon emissions and carbon offsets, while net zero aims to completely eliminate carbon emissions by generating renewable energy on-site.


Efficient HVAC Systems

Heating, ventilation, and air conditioning (HVAC) systems play a critical role in maintaining comfortable indoor environments in buildings. However, HVAC systems are also one of the most significant contributors to energy consumption and carbon emissions in buildings.


Building owners and managers can implement various energy efficiency measures to reduce energy consumption and carbon emissions from HVAC systems. These measures can include the following:

1. Upgrading to more efficient equipment

Replacing outdated or inefficient HVAC equipment with newer, more efficient models can significantly reduce energy consumption and carbon emissions. For example, upgrading to a high-efficiency air conditioner or heat pump can reduce energy consumption by up to 75% compared to older models.


2. Implementing building automation systems (BAS)

BAS can help optimize HVAC system performance by automatically adjusting temperature settings based on occupancy and outdoor weather conditions. BAS can also monitor energy consumption and provide data to help building owners and managers identify opportunities for further energy savings.


3. Improving building envelope

Improving the building envelope by adding insulation, sealing air leaks, and upgrading windows can help reduce the workload on HVAC systems and improve energy efficiency.


4. Conducting regular maintenance

Regular maintenance, such as cleaning and tuning HVAC equipment, can help ensure systems operate at peak efficiency.


5. Using renewable energy sources

Integrating renewable energy sources, such as solar panels or geothermal systems, can help offset energy consumption from HVAC systems.


By implementing efficient HVAC systems, building owners and managers can significantly reduce energy consumption and carbon emissions from buildings and help contribute to achieving net zero emissions.


Achieving Net Zero Emissions in Buildings

As buildings are responsible for a significant portion of global carbon emissions, transitioning to green energy sources and sustainable building practices is crucial in mitigating the impacts of climate change.


One of the key goals in this regard is achieving net zero emissions, where a building produces as much renewable energy on-site as it consumes over the course of a year. This requires a combination of energy efficiency measures, green energy sources, energy storage systems, ongoing monitoring, and continuous improvement. Now, let’s explore the various steps involved in achieving net zero emissions in buildings.

  1. Implementing Energy Efficiency Measures: Many energy efficiency measures can be implemented in buildings, including lighting upgrades, insulation improvements, and building envelope upgrades. For HVAC systems specifically, there are several measures that can be taken to improve efficiency, such as upgrading to high-efficiency equipment, implementing building automation systems, and conducting regular maintenance and tuning of existing systems.

  2. Integrating Green Energy Sources: To achieve net zero emissions, buildings must generate as much energy as they consume. This can be achieved by integrating green energy sources such as solar panels, geothermal systems, or wind turbines. These systems can be sized and designed to meet the energy needs of the building, and any excess energy can be sold back to the grid.

  3. Utilizing Energy Storage Systems: Energy storage systems can help optimize the use of green energy sources in buildings. By storing excess energy generated by green energy systems, facilities can use this energy during high-demand or low-green energy production periods. This can help reduce the reliance on grid energy and further reduce carbon emissions.

  4. Monitoring and Continuous Improvement: Achieving net zero emissions is not a one-time event but an ongoing continuous improvement process. Monitoring energy usage and carbon emissions on an ongoing basis can help identify areas for improvement and ensure that the building remains on track toward achieving net zero emissions.

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.

You can also subscribe to our monthly newsletter below for exclusive early access to Blade's Insights content, uncovering tomorrow's air quality advancements before they hit our Hub.

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