Back to School, Back to Clean Air: Ensuring Healthy Air in Classrooms

As another school year approaches, educators and parents are once again preparing classrooms for the return of students. In the wake of the COVID-19 pandemic – which highlighted the critical role of ventilation in reducing disease transmission – indoor air quality in schools has taken on renewed importance. Just last year, smoke from Canadian wildfires infiltrated multiple U.S. states and gave New York City the world's worst air quality, causing a spike in asthma-related emergencies. Events like these underscore that "back to school" must also mean back to clean air in our classrooms.

Yet ensuring healthy air in classrooms remains a challenge. The harsh reality is that many school buildings suffer from inadequate ventilation or pollution issues. According to U.S. Environmental Protection Agency estimates, nearly half of students and staff spend their school days breathing air polluted with mold, chemicals, allergens, and other contaminants inside schools. Aging infrastructure contributes significantly – a 2020 government report found that roughly one-third of U.S. public schools (about 36,000 schools) need to update or replace outdated heating, ventilation, and air-conditioning (HVAC) systems. These issues create an invisible problem that can have very visible consequences on student health and learning.

Why Clean Air in Classrooms Matters

Poor indoor air quality isn't just a facilities issue – it has tangible effects on students' health, attendance, and even academic success:

Asthma and Allergies: Children are especially vulnerable to asthma triggers in bad air. The presence of dampness or mold can increase the risk of asthma and other respiratory issues by 30–50%. Schools with poor ventilation often see more frequent and severe asthma attacks among students.
Spread of Illness: Stagnant, unfiltered air helps viruses and bacteria spread more easily. Studies find that poorly ventilated classrooms lead to more colds, flu, and other infectious outbreaks. In other words, cleaner air means fewer sick days for students (and staff).
Absenteeism: Unhealthy air contributes to students missing school. Conversely, improving classroom ventilation has been associated with significantly fewer absences and even fewer visits to the school nurse for respiratory symptoms. Every missed day impacts learning, so cleaner air directly supports better attendance.
Academic Performance: Perhaps most striking is the link between air quality and learning outcomes. Research shows that students in classrooms with higher outdoor air ventilation score better on standardized math and reading tests than those stuck in poorly ventilated rooms. Even moderate increases in indoor CO₂ (a sign of stuffy, unventilated air) have been tied to drops in cognitive function and attention – essentially, stale air can literally dull thinking. By contrast, when schools improve air quality, measurable gains in test performance often follow.

Why Do So Many Classrooms Have Bad Air?

Multiple factors can degrade a classroom's air quality:

Aging Buildings and Maintenance Issues: Many schools are old and have not been retrofitted with modern ventilation. Deferred maintenance (e.g. leaky roofs, old filters, faulty HVAC systems) leads to dampness and mold, which contaminate indoor air. In fact, a 2020 analysis found that 41% of school districts have HVAC systems in at least half of their schools that need an upgrade or replacement – highlighting how widespread this problem is.
Inadequate Ventilation: Even where mechanical ventilation exists, it may not be delivering enough fresh air. Studies show classroom ventilation rates regularly fall below the minimum standards needed for healthy air. In one California survey, nearly 85% of newly installed school HVAC systems failed to provide sufficient ventilation due to poor design or maintenance. Many classrooms simply rely on closed windows, resulting in CO₂ buildup and stuffy air.
Outdoor Pollution Seeping Indoors: The air outside the school can end up inside. Schools near busy roads or industrial sites may draw in vehicle exhaust, smog, and other pollutants. During events like wildfires, smoke can infiltrate classrooms through cracks or vents. Without high-quality filtration, these outdoor pollutants accumulate indoors (for example, fine particle levels can soar during a wildfire event, even far from the fire).
Indoor Sources of Contaminants: Within the school, certain materials and activities can pollute the air. Older buildings might still contain hazardous substances like asbestos or lead-based paints. The use of strong cleaning chemicals or paints can release volatile organic compounds (VOCs) into the air. Even everyday classroom items (markers, science lab chemicals, etc.) may emit irritant fumes. If ventilation is poor, such indoor pollutants linger and concentrate in the room.

How to Ensure Healthy Air in Classrooms

Every school can take steps to improve indoor air quality. Key strategies include:

Ventilation Upgrades: Bringing in more fresh outdoor air is fundamental. Schools should ensure their HVAC systems meet modern ventilation standards and are well-maintained, or use natural ventilation (open windows and doors) when conditions allow. Experts recommend keeping indoor CO₂ levels below about 1000 ppm (ideally under 900 ppm) to maintain air that's conducive to learning. If CO₂ in a classroom is regularly spiking above that range, it's a clear sign ventilation needs improvement – in the short term, teachers can open windows or vents to flush in fresh air, but longer-term the school may need to repair or upgrade its ventilation system.
High-Quality Filtration: Ventilation should be coupled with filtration to remove contaminants, especially in schools near pollution sources or during events like wildfire smoke. Upgrading HVAC filters to high-efficiency levels (e.g. MERV-13 filters, as recommended by the EPA) or deploying portable HEPA air purifiers can dramatically reduce indoor particulate pollution. Lowering levels of fine particulate matter (PM₂.₅) is critical – elevated PM₂.₅ not only irritates the lungs and triggers asthma, but has also been linked to impacts on brain health and even lower student test scores over time.
Source Control and Maintenance: Preventing pollution at the source keeps classroom air cleaner. For example, promptly fixing roof leaks or plumbing issues stops mold from growing (and spreading spores in the air). Choosing low-toxicity cleaning products and art supplies minimizes harsh chemical fumes. Schools should also enforce no-idling zones for buses and cars outside to cut down on exhaust entering the building. By removing or reducing these pollution sources, there is less burden on the ventilation and filter systems to keep the air safe.

Making the Invisible Visible: Monitoring Classroom Air

One of the most important steps is monitoring – you can't fix what you don't measure. Many indoor air problems go unnoticed until people start feeling ill or drowsy. By that point, learning may already be suffering. This is why experts now urge schools to deploy air quality monitors, especially for carbon dioxide, in classrooms as an early warning system.

CO₂ monitors are a simple but powerful tool. Carbon dioxide levels rise when people exhale in an enclosed space, so CO₂ is widely used as an indicator of whether a room is getting enough fresh air. In fact, many modern HVAC systems have built-in CO₂ sensors that trigger increased ventilation when CO₂ levels get too high. In a classroom without such a system, a portable monitor can tell you if CO₂ is creeping past the optimal ~800–1000 ppm threshold. Unfortunately, studies show most classrooms regularly exceed that level – one review found that typical classrooms averaged well over 1000 ppm CO₂, with some reaching peaks of 1500–5000 ppm during the day. At those concentrations, students and teachers often start to experience drowsiness, headaches, or lack of focus. Critically, research has confirmed that lower CO₂ concentrations (i.e. better ventilation) are associated with higher student cognitive performance.

By having a real-time CO₂ readout, schools can react quickly: for example, if a monitor shows CO₂ spiking mid-class, a teacher can crack open windows or doors to bring levels down before everyone gets groggy. Monitors also help verify that HVAC systems or purifiers are doing their job, and can indicate when filters need replacing.

Beyond CO₂, comprehensive air monitors can track fine particulate matter and other pollutants. This is especially useful if an external event (like wildfire smoke or nearby construction) is affecting the air – a PM₂.₅ sensor will reveal the influx of particles even when they're invisible to the eye. Armed with that knowledge, staff can decide to close outdoor air intakes, run air purifiers on high, or take other precautions to protect students. In short, monitoring takes the guesswork out of maintaining healthy air: it makes the invisible threats visible, so you can act on them in real time.

Halo Air: A New Tool to Protect Classroom Air

The good news is that innovative devices are making air quality monitoring easier than ever. Halo Air is one such solution – a smart air quality sensor designed for convenience and portability in schools (and anywhere else). Halo Air snaps onto the back of a smartphone, instantly turning it into a real-time air monitor for the surrounding environment. This compact gadget measures key parameters like carbon dioxide (CO₂) levels, particulate matter (PM₁.₀, PM₂.₅, etc.), volatile organic compounds (VOCs), temperature, and humidity, delivering insights right to an app on your phone.

For teachers, parents, or facility managers, using Halo Air is as simple as opening an app. You can watch the CO₂ number climb or fall in real time as you open a window or adjust a ventilation system – a powerful visual feedback on how effective your ventilation is. If indoor pollution creeps up (say, PM₂.₅ rises due to outdoor smoke, or CO₂ crosses 1000 ppm during a long lesson), Halo Air will send an alert so you know it's time to take action. Essentially, it takes the guesswork out of maintaining healthy air: this device makes the invisible visible, empowering you to respond before air quality deteriorates.

What makes Halo Air particularly valuable for schools is its portability. Unlike fixed wall-mounted sensors, Halo Air moves with students and staff throughout the day. A teacher can carry it from classroom to classroom, a parent can send it with their child to monitor different learning environments, or a facility manager can spot-check various areas of the school building. This mobility means you get air quality data from exactly where students are learning – whether that's in the main classroom, the library, the cafeteria, or even on the school bus.

Ready to protect your classroom's air quality? Halo Air is currently live on kickstarter.com, and early supporters are already joining this movement toward healthier learning environments. By backing the project, you'll be among the first to receive this cutting-edge tool and put it to work protecting the air quality in your child's school or your own classroom. Every educator and parent deserves access to real-time air quality data – because when we can see the problem, we can fix it.

Building a Community of Clean Air Advocates

Beyond individual monitoring, there's power in collective action. When multiple classrooms in a school use air quality monitors like Halo Air, it creates a comprehensive picture of the building's air health. Teachers can share data with facility managers to identify problem areas that need attention. Parents can advocate for improvements armed with concrete data showing where and when air quality issues occur.

Imagine a network of Halo Air devices throughout a school district, providing real-time insights into which buildings need ventilation upgrades, which classrooms have recurring air quality issues, and how external events like traffic or construction affect indoor air. This kind of data-driven approach to school air quality could revolutionize how we protect student health and optimize learning environments.

Join the growing community of educators and parents who are taking classroom air quality seriously. kickstarter.com and become part of the solution. Early supporters not only get priority access to the device but also help build a movement that prioritizes clean air in every classroom.

Taking Action for Cleaner Classroom Air

Clean air should be a given in every classroom, but the reality is that many of our schools need help achieving this basic standard. As we send our kids back to school, let's also commit to sending them back to healthy, breathable air. With awareness, smart strategies, and the right monitoring tools, we can ensure that "back to school" also means back to clean air.

Whether you're a teacher wanting to optimize your classroom environment, a parent concerned about your child's daily air exposure, or a school administrator looking to improve building-wide air quality, the solution starts with measurement. You can't improve what you don't monitor, and you can't monitor what you can't see.

The time for action is now. As students return to classrooms across the country, let's equip ourselves with the tools needed to protect their health and maximize their learning potential. kickstarter.com and join thousands of other parents, teachers, and clean air advocates who are committed to creating healthier learning environments for all students.

Together, we can make clean air in classrooms not just an aspiration, but a reality. Back the project today and help us put powerful air quality monitoring technology in the hands of every educator and parent who cares about the air our children breathe while they learn.

Sources: Improving Indoor Air in Schools – EPA; National Education Association report on school indoor air quality; Harvard T.H. Chan School of Public Health – Healthy Buildings research; Journal of Exposure Science & Environmental Epidemiology (2025) on ventilation and cognitive function; Moms Clean Air Force on CO₂ monitoring in schools; GAO report on school ventilation (2020).