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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.

Electromagnetic Filters vs. Traditional Pleated Filters: Which Is Right for You?

  • Writer: Ava Montini
    Ava Montini
  • Oct 24, 2024
  • 6 min read

As we spend more time indoors—whether at home, work, or school—the quality of the air we breathe has taken on greater importance. From reducing allergens to ensuring a healthier living environment, the role of air filtration systems in maintaining indoor air quality is undeniable.


For decades, pleated filters have been the go-to choice for many, but with growing awareness of sustainability and energy efficiency, new technologies are beginning to reshape the landscape.


One challenge with traditional pleated filters is the environmental impact. Each year, over 1 billion pleated filters are discarded into landfills in the U.S. alone, contributing to our growing waste problem. As we look for more sustainable ways to improve air quality, electromagnetic filters are emerging as a promising solution. With a focus on reducing waste, improving energy efficiency, and enhancing air filtration, these filters represent a shift in the way we protect our indoor spaces.


In this blog, we'll explore how electromagnetic filters differ from traditional pleated filters and discuss which option may best fit your space and needs.



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How Electromagnetic Filters Work

Electromagnetic filters use an electric charge to capture and remove particles from the air. Imagine how a magnet attracts metal shavings—this is similar to how an electromagnetic filter works, but instead of metal, it pulls in airborne particles like dust, pollen, smoke, and other tiny pollutants.


Here's how it works: as air flows through the filter, the filter generates an electric charge. This charge causes particles in the air to become electrically charged themselves. Once charged, these particles are drawn to oppositely charged surfaces within the filter, where they stick and are effectively trapped. This method is particularly effective for capturing very fine particles that might otherwise slip through traditional filters, such as microscopic pollutants and allergens.


Because electromagnetic filters rely on electric attraction rather than thick layers of material, they allow air to pass through more easily, resulting in better airflow with less resistance. This improves both the energy efficiency of your HVAC system and the overall quality of the air you breathe.


This process is highly effective at removing fine particles without needing dense physical barriers like pleated filters. However, since electromagnetic filters use electric charges, it's important to consider one additional factor—the potential for small amounts of ozone production. Fortunately, many high-quality electromagnetic filters are designed to minimize this, and there are certifications to ensure safe operation without harmful ozone levels.


Avoiding Ozone Production

Electromagnetic filters use an electric charge to attract airborne particles, making them highly effective at capturing both large and small pollutants. While this process is very efficient, it's important to be aware that some filters using electric charges can produce small amounts of ozone, a gas that forms when oxygen molecules (O2) react and recombine into O3 (ozone).


Fortunately, many modern electromagnetic filters are specifically designed to prevent this. Ozone is safe at higher levels in the atmosphere, but at ground level, it can be a lung irritant, especially for individuals with asthma or respiratory conditions. That's why it's always a good idea to choose filters that have been third-party certified to avoid ozone production. Certifications from trusted organizations like UL 2998 and CARB (California Air Resources Board) ensure that the filters meet strict safety standards so they won't release harmful levels of ozone while cleaning your air.


By selecting certified filters, you can enjoy better air quality and energy efficiency while having peace of mind that your system is operating safely and responsibly.



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How Traditional Pleated Filters Work

Pleated filters, on the other hand, work by physically blocking particles. Made of tightly woven fibrous material, these filters trap dust, dirt, and larger particles when air is pushed through them. The "pleats" in the filter increase its surface area, allowing it to capture more particles than a flat filter would.


While pleated filters are effective at catching larger particles like dust and pet dander, they do so at a cost: increased resistance. As more air passes through, the filter starts to clog, forcing your HVAC system to work harder to maintain airflow. This can lead to higher energy bills and more frequent filter replacements. Pleated filters are affordable upfront but may end up costing more over time due to frequent replacements and energy consumption.


Filtration Efficiency

Electromagnetic vs. Pleated Filters

When it comes to filtration efficiency, there's a stark difference between electromagnetic filters and pleated filters. Electromagnetic filters excel at capturing ultra-fine particles, which are tiny pollutants such as smoke particles, allergens, and even certain bacteria that can pass through traditional pleated filters. The filter's electric charge allows it to catch particles down to the micron level, which pleated filters often struggle with.


Pleated filters, on the other hand, are usually rated based on their MERV (Minimum Efficiency Reporting Value), which tells you how well the filter captures particles of varying sizes. Most pleated filters used in homes and businesses fall between MERV 8 and MERV 13, meaning they can capture dust, pollen, and mold spores but may let finer, viral particles slip through. Electromagnetic filters, however, don't rely on MERV ratings because their filtration method works differently. By using electrostatic energy, they achieve greater efficiency at capturing both large and small particles without compromising airflow.


For individuals with allergies or in environments where air quality is critical, such as healthcare or educational settings, electromagnetic filters provide a more comprehensive solution.


Energy Efficiency

Lower Pressure Drop with Electromagnetic Filters

One of the major advantages of electromagnetic filters is their low-pressure drop. Pressure drop refers to the resistance that air encounters as it moves through the filter. The higher the resistance, the harder your HVAC system has to work to maintain airflow. This is why many pleated filters, especially those with higher MERV ratings, can drive up energy costs.


Electromagnetic filters, on the other hand, cause very little resistance because they don't rely on thick layers of material to block particles. Instead, the electric charge actively pulls particles from the air without clogging up the filter or slowing down airflow. This means your HVAC system can run more efficiently, reducing energy consumption by as much as 30%. In the long run, this leads to lower energy bills and less wear and tear on your equipment, potentially extending the lifespan of your HVAC system.


Sustainability and Waste Reduction

Sustainability is becoming a key factor in decision-making for many businesses and homeowners. Traditional pleated filters contribute to a significant amount of waste, as they need to be replaced every 1 to 3 months, depending on air quality and usage. Each year, over 1 billion pleated filters end up in landfills in the United States alone.


Electromagnetic filters offer a much more sustainable solution. Since they don't need to be replaced as frequently, they generate far less waste. In many cases, they are designed to be cleaned and reused, reducing the need for constant replacements. This cuts down on waste and saves money in the long run. Electromagnetic filters are an excellent choice for environmentally conscious businesses or homeowners looking to reduce their carbon footprint.


Maintenance and Cost

At first glance, pleated filters appear to be the more affordable option. They are inexpensive to buy and widely available. However, the cost of replacing pleated filters every few months quickly adds up. You have to factor in the cost of the filter itself and the labor involved in changing them, especially in large commercial spaces. Over time, pleated filters can become a costly option, especially when you consider the energy costs associated with the increased pressure drop they create.


Electromagnetic filters, on the other hand, are more expensive upfront but require significantly less maintenance. They last longer and often don't need to be replaced as frequently, if at all. Many electromagnetic filters are designed to be self-cleaning, meaning you won't need to spend as much time or money on filter replacements. Over time, the long-term savings from reduced energy consumption and fewer replacements make electromagnetic filters a cost-effective choice.


Indoor Air Quality (IAQ) Impact

Improving indoor air quality (IAQ) is one of the most important functions of any air filtration system. Both pleated and electromagnetic filters can help improve IAQ, but electromagnetic filters offer a significant advantage when it comes to trapping the smallest, most harmful particles.


For example, maintaining high indoor air quality in a school or healthcare facility is critical for the health and safety of students, patients, and staff. Electromagnetic filters are more effective at capturing pollutants like smoke, mold spores, and allergens, which are more challenging for pleated filters to trap. This makes electromagnetic filters the better choice for environments where air quality directly impacts health.


While effective at catching larger particles like dust and pet dander, pleated filters can sometimes allow finer particles to pass through. This means they may not provide the same level of protection in environments where air quality is paramount, such as hospitals, schools, and homes with allergy sufferers.

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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