June read — Schools IAQ factsheet
There is just one topic for this month. That is because it is a bit long and worth of some time and energy.
This month's item of focus is the Schools IAQ Fact Sheet Overview, coming to us from ASHRAE and the USGBC. The document itself is free to access at the link. It is 26 pages and worth the time it takes to go through the pages. I will try to summarize some key points here, but it is an informative read — I do recommend going through it and keeping a copy handy.
To clarify, there is a full series of factsheets for School IAQ and this document is an overview of all these factsheets.
Why Children Are Especially Vulnerable
Children face unique risks when exposed to poor indoor air quality that adults do not experience. Their developing respiratory systems, higher breathing rates relative to body weight, and less efficient nasal filtering make them particularly susceptible to airborne contaminants.
The consequences start from simple discomfort to poor learning, headaches, and drowsiness, and infectious and non-infectious (asthma and allergies to name some) diseases.
Ensuring Healthy School Air
Understanding the Standards
At present, three key ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards guide school air quality management:
ASHRAE Standard 62.1 establishes minimum outdoor ventilation requirements:
- Classrooms: ~15 cubic feet per minute (cfm) per person
- Offices: ~17 cfm per person
- Cafeterias: ~9 cfm per person
- Gymnasiums: ~46 cfm per person
ASHRAE Standard 241 focuses specifically on infection risk management through (equivalent) clean airflow rates:
- Classrooms: 40 cfm per person
- Offices: 30 cfm per person
- Cafeterias: 60 cfm per person
- Gymnasiums: 80 cfm per person
ASHRAE Standard 44 provides guidance for protecting indoor air quality during wildfire and smoke events.
And if you are wondering like me as to what cfm is in terms of litres per second, an easy (and close enough) conversion is to halve the value.
The Critical Difference: Volume vs. Person-Based Ventilation
A crucial distinction exists between measuring ventilation by air changes per hour (ACH) versus per-person rates. This becomes especially important in smaller, less densely occupied spaces where person-based calculations provide more accurate air quality management. The CDC’s recommendation of 5 air changes per hour serves as a baseline, but individual occupancy patterns require tailored approaches. ASHRAE is not recommending the 5 ACH approach. The person-based ventilation will give you slightly more ventilation flow for dense occupancies like classroom and a lot less for sparsely occupied small offices (meaning less energy use and similar protection).
Proven Strategies for Cleaner School Air
1. Proper Ventilation Systems
The foundation of good school air quality begins with adequate ventilation that meets minimum standards (in this case, Standard 62.1). Natural ventilation through strategically opened windows and doors can be highly effective, particularly on windy days or when significant temperature differences exist between indoor and outdoor environments. However, classroom under-ventilation remains disturbingly common due to inadequate installation verification, deferred maintenance, and misguided energy-saving attempts.
2. High-Efficiency Filtration
Modern filtration technology offers powerful solutions for cleaner air. High-efficiency MERV (Minimum Efficiency Reporting Value) filters effectively capture tiny airborne particles, including infectious aerosols and fine particulate matter.
Importantly, higher MERV ratings do not necessarily mean a higher pressure drop (which would mean a requirement for higher system fan power, more energy use…). Filter construction plays a crucial role — deeper or electrostatically charged filters can maintain lower pressure drops while providing superior filtration. So, you need a qualified professional in your corner and ask the supplier for options and manufacturer data regarding the pressure drops of filters. You will quite likely find a MERV 11–13 filter with similar pressure-drop characters that your current MERV 8 has.
For schools in wildfire-prone regions, you may need to combine high-efficiency MERV filters with sorbent filters to address both particulate matter and gas-phase pollutants.
3. Supplemental Air Cleaning Technologies
When standard ventilation and filtration are not sufficient, additional technologies can bridge the gap:
HEPA Air Cleaners: In room, portable air cleaners, whether using HEPA filters or a DIY design with MERV 13 filters (like CR Boxes), can significantly reduce exposure to particulate matter and infectious aerosols in a classroom. The placement advice in the factsheet it to keep it closest to the person speaking (i.e., the teacher) and about one meter from walls and open windows, doors.
Noise can be a concern as is deploying a filter that suits your classroom size and needs. So, look at manufacturer data and decide carefully.
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Germicidal Ultraviolet (GUV): UV-C technology effectively inactivates airborne pathogens. Upper-room GUV systems require professional installation with strict safety protocols — UV-C levels must not exceed 0.4 μW/cm² anywhere in occupied spaces, and units must be mounted at least 7 feet above floor level. The current factsheet only discusses the 254 nm UVC, not the far UVC 222 nm as there is work ongoing regarding its safety and use in public spaces.
4. Smart Monitoring and Assessment
Continuous air quality monitoring enables proactive management before problems escalate. The advice is to have monitoring systems with:
- NDIR (Non-Dispersive Infrared) CO2 sensors
- Integration capabilities with building automation systems where possible
- Regular calibration following manufacturer recommendations
- Data logging for trend analysis and system optimization
CO2 monitoring serves as an excellent proxy for ventilation effectiveness, as elevated levels often indicate inadequate air exchange and potential accumulation of other contaminants. However, this means you need to rely on continuous records instead of just a point-in-time data.
The Professional Assessment Imperative
School districts should engage certified Testing, Adjusting, and Balancing (TAB) providers to evaluate HVAC system performance. Reputable providers hold certifications from organizations like NEBB (National Environmental Balancing Bureau), TABB (Testing, Adjusting, and Balancing Bureau), or AABC (Associated Air Balance Council).
These professionals follow established standards such as ASHRAE 111, use calibrated equipment, and provide detailed reports with performance measurements and improvement recommendations.
Preparing for Environmental Challenges
Wildfire Smoke Response
Schools in wildfire-prone regions require comprehensive smoke readiness plans. And you cannot make it up on the go. This does require some forethought and preparation. Make sure there are:
- Functional outdoor air dampers capable of stopping intake during smoke events
- Properly maintained filtration systems
- Building pressurization capabilities to prevent infiltration, where possible
- PM2.5 monitoring with targets of keeping indoor levels at 20% or less of outdoor concentrations
- In-room air cleaners for additional protection when needed
The Economic Reality
Improving school air quality requires investment, but the costs are manageable. Treating outdoor air — including heating, cooling, and humidity control — costs approximately $10 per child, annually, as stated in the factsheet. When weighed against the benefits of reduced illness, improved learning outcomes, and decreased energy costs from optimized systems, this investment delivers substantial returns.
Taking Action: What You Can Do
For Parents:
- Ask your school about their IAQ management plans
- Advocate for regular HVAC system assessments
- Support funding initiatives for air quality improvements
For Educators:
- Monitor classroom air quality visually through available systems — it affects your health as much as the children’s
- Report persistent air quality concerns to facilities management
- Understand your building’s ventilation systems and capabilities
- Take parents into confidence and work together instead of at cross purpose
For School Administrators:
- Implement comprehensive IAQ monitoring programs
- Establish relationships with certified TAB providers
- Develop emergency response plans for air quality events
- Prioritize filter maintenance and upgrades in budget planning
And all of these require that the policy makers create a landscape that can fund and facilitate these changes as well as promote research towards optimizing classroom indoor climate.
My perspective
The investment in school air quality is not just about buildings and systems — it’s about investing in our children’s futures.
A few things I would like to see in the subsequent versions of this factsheet:
- Advice on natural ventilation design for classrooms. Just because a room has doors and windows, does not mean there will be enough ventilation. It needs to be designed for in terms of window sizing, where windows face, building layout, room depth and window opening portions.
- Interaction between air quality needs and thermal comfort needs.
