Introduction: The Post-COVID Indoor Air Quality Crossroads
During the COVID-19 pandemic, schools across the United States made unprecedented investments in indoor air quality (IAQ). Federal relief funding enabled districts to purchase thousands of medical-grade HEPA air purifiers to protect students, teachers, and staff from airborne viruses. These decisions were correct, science-based, and lifesaving.
Fast-forward to today: the emergency funding has largely dried up, budgets are tight, and many schools are now at a critical crossroads. The air purifiers are still there—but the filters inside them are aging, expired, or completely exhausted.
This creates a simple but consequential decision for school leaders:
• Replace the filters and continue realizing the health and attendance benefits • Run the units with expired filters that no longer work • Put the units into storage • Discard them entirely
From a health, financial, and educational standpoint, filter replacement is clearly the best investment.
HEPA Air Purifiers Only Work If the Filters Work
A HEPA air purifier is not a permanent solution by default. Its effectiveness depends entirely on the condition of its internal filters.
When filters are expired:
• Particle capture efficiency drops dramatically • Mold spores and allergens pass through • Odors and chemical vapors are no longer absorbed • Viruses and fine aerosols are no longer effectively reduced
In other words, an air purifier with an expired filter is essentially a fan in a box.
Running purifiers with spent filters creates a false sense of protection and undermines the original investment.
The Real Cost of Not Replacing Filters: Absenteeism and Illness
A growing body of research shows that improved indoor air quality in schools leads to:
• Reduced respiratory illness • Fewer asthma exacerbations • Lower allergy burden • Measurable reductions in student absenteeism
Studies summarized by Clean School Air and other public-health researchers show that classrooms using HEPA air purifiers experience meaningful reductions in illness-related absences, with some studies reporting absenteeism reductions in the range of 10–15% or more.
Even a modest reduction in absenteeism has outsized impacts:
• More consistent learning • Improved academic outcomes • Increased state attendance-based funding • Reduced strain on substitute teachers and staff
From a purely financial standpoint, keeping students in seats is one of the highest-ROI investments a school can make.
Storage Is Not a Neutral Option
Many districts have responded to budget pressure by placing air purifiers into storage.
This may feel fiscally responsible—but it creates several hidden costs:
• The original capital investment is wasted • Health protections are eliminated • Equipment degrades over time in storage • Redeployment costs increase later
A stored air purifier provides zero health benefit and represents sunk cost without return.
Throwing Units Away Is the Most Expensive Option
Discarding air purifiers because of filter costs is equivalent to scrapping a school bus because it needs new tires.
The purifier housing, motor, and engineering are still fully functional. The filter is a consumable component by design.
Replacing filters costs a fraction of replacing entire units—and avoids repeating procurement, training, and deployment cycles.
Why Filter Replacement Is the Smart, Defensible Choice
Replacing filters:
• Extends the life of existing assets • Preserves health and safety gains • Protects prior public spending • Costs far less than new equipment • Continues to reduce absenteeism and illness
From a risk-management perspective, continuing to operate air purifiers properly is also easier to defend than abandoning them entirely.
The Problem With Short-Life, High-Maintenance Purifiers
Not all air purifiers are equal.
Many units purchased during COVID require:
• Annual or semi-annual filter changes • Classroom disruption during maintenance • Multiple filters per unit • Frequent monitoring and tracking
When funding disappeared, these systems became unsustainable—and many quietly stopped being maintained.
IndoorDoctor’s Recommendation: Austin Air
IndoorDoctor recommends Austin Air medical-grade HEPA purifiers for schools because they are specifically designed for long-term, low-maintenance use.
Key advantages include:
1. Five-Year Filter Life
Austin Air systems use large, high-capacity HEPA and activated carbon filters designed to last up to five years under normal classroom conditions.
This dramatically reduces:
• Annual budget pressure • Maintenance scheduling • Risk of expired filters
2. Plug-and-Play Deployment
No retrofits. No installation. No training burden.
Units are simply plugged in and immediately effective.
3. No Classroom Disruption
Filters are replaced infrequently and without significant noise, dust, or downtime—minimizing instructional disruption.
4. Wide-Spectrum Contaminant Control
Austin Air systems are effective against:
• Mold spores • Allergens • Odors • Chemical vapors • VOCs • Fine particulate matter • Airborne viruses including RSV, COVID-19, and influenza
5. Medical-Grade Performance
These are not consumer gadgets. They are medical-grade systems used in hospitals, clinics, and schools where reliability matters.
Budget Reality: Filters vs. Absenteeism
School leaders are understandably cautious with limited funds. But the real question is not:
“Can we afford to replace the filters?”
It is:
“Can we afford the absenteeism, illness, and learning loss if we don’t?”
Replacing filters is predictable, controllable, and far less expensive than:
• Chronic student absences • Increased nurse visits • Teacher sick days • Parent dissatisfaction • Academic disruption
A Clear Recommendation for School Decision-Makers
Schools that already own HEPA air purifiers should:
- Inventory existing units
- Determine filter age and condition
- Replace expired or near-expired filters
- Prioritize long-life, low-maintenance systems
- Avoid storage or abandonment of functional equipment
IndoorDoctor strongly recommends budgeting for filter replacement rather than equipment replacement.
Conclusion: Protect the Investment, Protect the Students
The COVID era proved something critical: indoor air quality matters.
That truth did not expire with federal funding.
Schools now face a choice that will quietly but powerfully affect student health, attendance, and learning for years to come. Replacing HEPA filters is not a luxury—it is a continuation of a smart, evidence-based investment already made.
IndoorDoctor is available to help districts:
• Evaluate existing air purifiers • Determine filter replacement needs • Recommend long-life solutions • Support healthier classrooms with minimal disruption
Replacing the filters is not just the best option—it is the only option that makes sense.
Evidence, Expertise, and Trust
IndoorDoctor’s recommendations are grounded in peer-reviewed research, field experience, and established public-health guidance. As an environmental engineering firm specializing in indoor air quality, mold, and post-remediation verification, IndoorDoctor has evaluated thousands of buildings—including schools, healthcare facilities, and public buildings—across diverse climates and conditions.
Our guidance reflects:
• Established medical and environmental engineering principles • Independent academic research on air filtration and absenteeism • Real-world performance of HEPA and activated carbon systems in occupied classrooms • Risk management considerations for school administrators and boards
References and Citations
- Clean School Air. Research on Air Filtration, Ventilation, and Student Health Outcomes. Summarizes peer-reviewed studies linking improved indoor air quality and HEPA filtration to reductions in illness and absenteeism in schools and childcare settings. https://cleanschoolair.org/research
- Resources for the Future (RFF). The Effect of Air Purifiers in Schools. Cluster randomized controlled trial demonstrating reduced particulate matter and approximately 12.5% reduction in student absenteeism. https://www.rff.org/publications/working-papers/the-effect-of-air-purifiers-in-schools/
- U.S. Environmental Protection Agency (EPA). Indoor Air Quality and Student Health. EPA guidance outlining the relationship between indoor air quality, respiratory illness, and school attendance. https://www.epa.gov/iaq-schools
- World Health Organization (WHO). Roadmap to Improve and Ensure Good Indoor Ventilation in the Context of COVID-19. Establishes airborne transmission risk and the role of filtration and ventilation in reducing viral spread.
- American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Position Document on Filtration and Air Cleaning. Technical standards supporting HEPA filtration for removal of fine particles, allergens, and airborne pathogens.