Update on HCPSS Measures for Enhancing Air Quality in School Buildings, August 26, 2021

August 26th, 2021

Please also see What schools don’t have MERV 13 air filters and what is being done to ensure safe indoor air quality?

HCPSS is committed to ensuring a safe learning environment for all students and staff. Throughout the COVID-19 pandemic, HCPSS has relied on the guidance of the Centers for Disease Control and Prevention (CDC), American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and other agencies in implementing measures to maximize air quality and other aspects of a healthy building environment.

Several concerns have been raised by families related to HEPA fan/filtration units, air circulation, and other items related to the health of air in our schools. This update provides a comprehensive overview of the measures in place and to provide families and staff the assurance that HCPSS has deployed a combination of strategies consistent with the most current CDC guidance for ventilation in buildings. The CDC also recommends auxiliary air cleaning in higher risk settings and in areas where outdoor ventilation is not available. In addition, in guidance issued for parents this week, the Johns Hopkins Bloomberg School of Public Health states that if schools are unable “to meet updated COVID filtration guidance (including MERV-13 filters and 6 air changes per hour), urge them to add individual HEPA filtration units to their classrooms.”

HCPSS has implemented a combination of measures to improve building ventilation at each school, including portable HEPA fan/filtration units to provide auxiliary air cleaning in each school’s COVID isolation room, and in portable classrooms where outdoor air is not introduced through the HVAC unit. The HVAC units serving all student-occupied areas of HCPSS school buildings and all other portable classrooms provide outdoor air ventilation. In addition, HCPSS has additional portable HEPA fan/filtration units on order to deploy as necessary, however, all spaces that currently require one due to inability to meet ventilation guidelines are fully equipped with portable HEPA fan/filtration units.

Specifically, the following improvements to building ventilation have been implemented at all HCPSS schools:

• Air filters having a minimum efficiency reporting value (MERV) rating of MERV 13 have been installed in all HVAC units wherever possible. 

• Outdoor air ventilation has been maximized at all schools by ensuring that outdoor air dampers, airside economizers, and exhaust fans are working properly in all HVAC units. Air bypass around air filters has also been addressed in all HVAC units to ensure that all air passes through the air filters and not around them.

• HVAC system run times have been extended, starting two hours before school occupancy through two hours after school occupancy, to flush schools with additional outdoor air ventilation prior to students’ arrival and after their departure.

• HVAC units provide approximately six room air changes per hour during student-occupied hours.

• Demand-controlled ventilation has been disabled to ensure that 100% of the outdoor airflow designed for each space will be continuously delivered whenever schools are occupied. 

• HVAC system energy recovery units have been disabled during times of non-extreme summer and winter conditions to prevent any exhaust air from being re-entrained into the outdoor air ventilation.

• Portable high-efficiency particulate air (HEPA) fan/filtration units have been installed in the isolation room in each school’s health suite, as described above. 

• Carbon dioxide (CO2) sensors with data logging capabilities have been installed in all school cafeterias. The level of CO2 in the room air, measured in parts per million (ppm) CO2, provides an indication of the effectiveness of the outdoor air ventilation in diluting airborne contaminants.