top of page

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

Tags

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.

5 Easy Air Quality Tips Teachers and Staff Can Implement for a Healthy Classroom This Year

  • Writer: Ava Montini
    Ava Montini
  • Sep 4, 2024
  • 7 min read

As schools reopen for a new academic year, one often overlooked factor that plays a crucial role in students' health, performance, and overall well-being is the air they breathe. Indoor air quality (IAQ) in classrooms impacts more than just comfort—it can directly influence student absenteeism, concentration, and cognitive function. According to the World Health Organization (WHO), poor indoor air quality can lead to serious respiratory issues, with children being especially vulnerable due to their developing lungs and higher breathing rates. In colder months, when natural ventilation is limited, maintaining clean air becomes even more challenging.


This year, as schools continue to prioritize health and safety in light of lingering viral concerns, teachers and staff are on the front lines of managing classroom environments. While upgrading HVAC systems and installing air purification technology may be on the long-term agenda, there are immediate, simple steps that can have a significant impact on classroom air quality. By adopting these easy, actionable strategies, educators can ensure that their students learn and grow in a healthy space all year long—especially when colder weather forces more time indoors.


Here are five practical tips that teachers and school staff can easily implement to improve air quality and create a healthier learning environment.



ree

1. Open Windows for Fresh Air (Even in Short Bursts)


As temperatures drop, it’s common for classrooms to be closed up tightly, reducing the flow of fresh air. However, fresh outdoor air is vital to diluting indoor pollutants, like carbon dioxide (CO2), dust, and allergens, all of which can build up quickly in a crowded space. Even a few minutes of ventilation can refresh the air and improve the room’s overall air quality.


  • Tip: Try cracking windows open during class breaks, lunchtime, or after school for 5–10 minutes. When paired with your classroom’s HVAC system, this can help flush out stagnant air and introduce fresh oxygen into the room without losing too much heat.


  • Why it matters: According to the EPA, classrooms with good ventilation see reduced incidences of headaches, fatigue, and respiratory issues. Regular air exchange also helps remove viruses and allergens, making it especially important during cold and flu season when illnesses spread rapidly through schools.


While many schools are upgrading their HVAC systems to increase ventilation, teachers can make a difference by using windows strategically to complement these systems.



ree

2. Move Classes Outdoors When Possible


A classroom isn’t always defined by four walls. Outdoor learning not only provides students with a change of scenery but also drastically improves their exposure to fresh air and sunlight—two natural defenses against poor indoor air quality. Outdoor lessons are especially beneficial during the fall and early winter before temperatures become too harsh.


  • Tip: Plan outdoor activities such as reading time, group discussions, or even art projects. Outdoor spaces like courtyards, playgrounds, and gardens can serve as temporary classrooms for a variety of lessons.


  • Why it matters: Research published in the journal Environmental Health Perspectives shows that outdoor air is generally much cleaner than indoor air, particularly in urban environments. Being outside also reduces exposure to indoor allergens, VOCs, and carbon dioxide buildup that can accumulate in closed spaces over time.


Furthermore, studies have shown that outdoor learning helps increase engagement and can have cognitive benefits, improving focus and creativity among students.



ree

3. Declutter Classrooms to Minimize Dust and Allergens


Dust mites, mold spores, and other allergens thrive in cluttered environments, which is why maintaining an organized, tidy classroom is crucial for good IAQ. When books, papers, and materials pile up, they can trap dust and prevent proper air circulation, creating a breeding ground for allergens that affect students with respiratory issues or allergies.


  • Tip: Regularly clean and declutter shelves, window sills, and desks. Encourage students to help by keeping their personal areas tidy, and store rarely used items in sealed containers to limit dust accumulation.


  • Why it matters: Clean, well-organized classrooms reduce the number of airborne particles and allergens, which can significantly improve students' breathing comfort. According to the American Lung Association, minimizing exposure to dust and mold is especially important for children with asthma, which affects about 6 million children in the U.S.


A clean space not only helps with IAQ but also promotes better concentration and productivity, creating an overall more efficient learning environment.




ree

4. Use Portable Air Purifiers in Key Areas


Not every classroom is equipped with state-of-the-art air filtration systems, but portable air purifiers provide a simple and effective way to ensure cleaner air. Modern air purifiers with HEPA filters are designed to capture 99.97% of particles as small as 0.3 microns, including dust, pollen, pet dander, and even airborne viruses. For older classrooms with limited ventilation or those in high-traffic areas, air purifiers can make a noticeable difference.


  • Tip: Place a portable air purifier in the classroom's busiest areas—like near the door or at the center of the room. Look for purifiers with HEPA filters, which are particularly effective at removing particles that could otherwise circulate for hours.


  • Why it matters: According to the ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers), using air purifiers is a proven method of improving air quality in enclosed spaces, especially during times when HVAC systems may not be sufficient to remove all contaminants.


Even a single purifier can help keep the air cleaner and healthier, especially during the colder months when windows remain closed and natural airflow is limited.




ree

5. Promote Hygiene and Clean Air Practices


Good air quality goes hand in hand with classroom cleanliness. Encouraging students to practice proper hygiene is one of the easiest and most effective ways to prevent the spread of germs and reduce airborne contaminants.


  • Tip: Place hand sanitizers and tissues in convenient areas around the classroom and encourage students to cover their mouths when coughing or sneezing. Additionally, consider teaching students about the importance of IAQ and how simple actions like keeping their desks clean can help maintain it.


  • Why it matters: The Centers for Disease Control and Prevention (CDC) emphasizes the link between proper hygiene and reduced airborne viral transmission. In a classroom setting, where students are often in close contact, maintaining good hygiene helps protect both air quality and overall health.


By teaching students the value of these practices, educators can create a cleaner, healthier classroom environment that benefits everyone.


Embracing Cleaner Air for Better Learning


The importance of indoor air quality (IAQ) in classrooms cannot be overstated. As students spend an average of 1,000 hours per year in school, the quality of the air they breathe can significantly impact their health, cognitive abilities, and overall well-being. Poor IAQ has been linked to a range of health issues, including asthma, respiratory infections, and allergies—conditions that can lead to increased absenteeism and lower academic performance. Research from the Harvard T.H. Chan School of Public Health found that poor indoor air quality, particularly high levels of CO2, can negatively affect cognitive function and decision-making abilities, which are critical for learning and concentration.


As we head into the colder months, when windows are often sealed and ventilation is reduced, maintaining clean, healthy air in classrooms becomes more challenging yet more important. Studies show that indoor air can be up to five times more polluted than outdoor air, with contaminants like dust, volatile organic compounds (VOCs), mold spores, and even airborne viruses accumulating in closed spaces. This makes it essential for schools to adopt strategies that ensure good air quality even when natural ventilation is limited.


The Connection Between Air Quality and Academic Performance


Air quality in classrooms has a direct impact on student performance. Research published in the journal Environmental Health Perspectives indicates that improved IAQ can enhance cognitive functions related to problem-solving, memory, and concentration. In schools with better ventilation, students have been shown to score 5-10% higher on standardized tests. Additionally, a study by the Lawrence Berkeley National Laboratory found that improving IAQ could reduce absenteeism by as much as 2-3%, which is particularly important during cold and flu season when respiratory illnesses are more common.


Ventilation plays a critical role in reducing the concentration of indoor pollutants, especially during colder months. Stale air leads to a buildup of CO2 and other harmful substances, which not only affect health but also contribute to fatigue and inattentiveness in students. According to the EPA, classrooms with high CO2 levels above 1,000 parts per million (ppm) experience a significant drop in attention span and decision-making capacity among students. This makes it crucial to refresh the air through simple steps like opening windows or using air purifiers, even for short bursts of time.


Reducing Airborne Illnesses with Better IAQ


Indoor air quality also influences the spread of airborne illnesses, such as the flu, colds, and other respiratory viruses, including COVID-19. During colder months, when students and staff spend more time indoors in close quarters, the likelihood of transmission increases. The Centers for Disease Control and Prevention (CDC) emphasizes that proper ventilation is a key preventive measure against airborne transmission of viruses. By ensuring a constant flow of fresh air and using high-efficiency filters like HEPA, schools can significantly reduce the spread of airborne pathogens.



Long-Term Benefits of Decluttering and Hygienic Practices


Maintaining a clean, clutter-free classroom is more than just an aesthetic choice—it directly impacts IAQ. Dust, dander, and mold spores accumulate on surfaces and in corners, leading to poor air quality that can trigger allergic reactions or asthma attacks in students. Regular cleaning and organization help reduce these pollutants, contributing to better air circulation and fewer airborne irritants. According to the American Lung Association, children with asthma are particularly vulnerable to poor indoor air quality, and classrooms with excessive dust and allergens can exacerbate their condition, leading to more frequent asthma attacks and hospital visits.


Promoting hygiene, such as encouraging handwashing, covering coughs, and keeping surfaces sanitized, also plays a crucial role in maintaining clean air. Hygienic practices help reduce the spread of germs and contaminants that can become airborne. A 2013 study published in the journal Pediatrics found that improved hygiene and handwashing practices in schools led to a 31% reduction in respiratory illnesses among students, highlighting the connection between hygiene and air quality.


A Sustainable Approach to Healthier Classrooms


By taking simple steps—opening windows, decluttering, using air purifiers, and promoting good hygiene—teachers and staff can have a substantial impact on indoor air quality. These efforts are not just short-term fixes; they lay the groundwork for long-term health benefits for students and staff alike. Healthier students are more engaged, more focused, and less likely to miss school due to illness, leading to better academic outcomes over time.


Additionally, improving IAQ aligns with broader sustainability goals. Reducing the use of chemical cleaners and VOC-emitting materials in classrooms and opting for greener alternatives can reduce overall pollution levels and promote a more sustainable learning environment. Schools that prioritize IAQ are investing not only in the health of their students but also in the future of education, creating environments where students can thrive both academically and physically.


Ultimately, cleaner air means better learning, healthier students, and a brighter future.

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.

Insights Hub

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor 

Lorem ipsum dolor sit amet cotetur 

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor 

Lorem ipsum dolor sit amet cotetur 

Lorem ipsum dolor sit amet, consec tetur adipiscing elit. Sit quis auctor 

Lorem ipsum dolor sit amet cotetur 

bottom of page