Air quality is commonly measured using the Air Quality Index (AQI), a tool developed by the United States Environmental Protection Agency (EPA) to communicate how clean or polluted the air is and the potential health effects associated with current conditions. The AQI takes into account several pollutants, including particulate matter (such as wildfire smoke and dust), ozone, and other airborne contaminants.

AQI values range from 0 to 500, with higher numbers indicating greater levels of air pollution and increased health concerns. Schools can use AQI forecasts and real-time monitoring tools to help guide decisions about outdoor activities, athletics, recess, and other school events.

Local air districts may also use additional monitoring methods or regional tools to assess air quality conditions. Schools are encouraged to consult local public health and air quality agencies for region-specific guidance.

Outdoor air quality is one factor schools should consider when determining whether to modify operations or close a school site. Decisions should be based on local conditions, indoor air quality, the ability to maintain a safe learning environment, and the needs of students and staff. School closure decisions remain a local decision for each district or school site.

Before making a decision to close a school due to poor air quality, schools may consider:

• Indoor air quality and the effectiveness of ventilation and filtration systems
• Whether indoor spaces provide cleaner air than outdoor environments
• The ability to safely supervise students indoors
• The health needs of students and staff, particularly individuals with respiratory or heart conditions
• Access to meals, counseling, nursing, and student support services
• The impact of closures on families and childcare needs
• Local emergency conditions and recommendations from public health or emergency management officials

Schools may also choose to collaborate with the local Emergency Operations Center (EOC), Imperial County Public Health, Imperial County Air Pollution Control District, Imperial County Office of Education (ICOE), and other community partners when evaluating significant air quality events or operational impacts. Coordination with local partners may help support situational awareness, communication, and informed decision-making during rapidly changing conditions.

Schools with properly functioning HVAC systems and effective air filtration may be able to provide safer indoor environments during smoke or poor air quality events than some homes or community settings.

School districts should also establish communication procedures for notifying families, staff, and community partners regarding closures, activity modifications, or other operational changes related to air quality conditions.

School closures due to poor air quality should be reported using the School Emergency Reporting System (SERS).

During periods of poor air quality, schools may take steps to improve indoor air quality and reduce exposure to smoke, dust, and other airborne pollutants. Indoor spaces may provide safer environments for students and staff when air filtration and ventilation systems are functioning effectively.

Schools may consider the following strategies to support cleaner indoor air:

• Maintain and regularly service HVAC systems
• Use medium or high-efficiency air filtration, including MERV-13 filters when compatible with the system
• Utilize portable HEPA air cleaners in classrooms, health offices, and other occupied spaces when available
• Identify and prioritize use of cleaner indoor spaces for students and staff during smoke or air quality events
• Keep doors and windows closed when outdoor air quality is poor, if safe indoor temperatures can be maintained
• Reduce introduction of outdoor air by limiting outside air intake during smoke events and reopening ventilation systems after conditions improve
• Avoid devices marketed as “ionizers” or “ozone generators”, which may create additional air quality concerns

Schools may also consider using indoor air quality monitoring tools or consulting with facilities staff, local air districts, or environmental health professionals when evaluating building conditions during prolonged poor air quality events.