OCDSB Ventilation and Indoor Air Quality

The OCDSB has been consistent with our approach in prioritizing indoor air quality and the health and safety of the occupants of our facilities. 

Our experienced HVAC design professionals are in constant communication with our consulting engineers and public health organizations to ensure we are following their guidance and adhering to the latest ventilation and Indoor Air Quality (IAQ) standards. During the pandemic, with an increased focus on IAQ and reducing the transmission risk of airborne contaminants, additional measures were implemented, many of which remain in place. Lessons learned during the pandemic have resulted in new industry standards (via ASHRAE) and new guidance from the public health organizations. 

There is a broad variation of HVAC system complexity and design in our facilities, often with different types and ages of systems in one facility. Each school’s HVAC systems are reviewed on a regular basis to determine what measures, specific to the individual school, can be implemented to improve system operation and indoor air quality.

With the goal of optimizing air quality and reducing the transmission risk of infectious aerosols, we focus on two areas: increasing ventilation rates and increasing air filtration levels. The characteristics of each particular HVAC system determines which measures are implemented. As an example, if it is not feasible to increase ventilation rates at a particular school due to the nature of the HVAC system and/or physical constraints, special high efficiency air filtration systems are installed (typically Ultra Violet or HEPA filtration units).

The Board has invested heavily over the past 10 years in our central Building Automation System (BAS). The BAS enables us to monitor and control HVAC equipment and monitor the indoor environment. This allows us to quickly identify any malfunctioning HVAC equipment or problematic conditions. Utilizing the BAS, we continue to closely monitor the indoor environment and adjust HVAC systems operations to optimize the indoor air quality. At each school, CO2 levels are monitored and alarms are automatically generated if levels reach the upper limits. While CO2 readings are not a measure of infectious aerosols transmission risk, it can serve as a proxy measure of overall ventilation and alerts our staff of any potential issues.

Examples of actions taken in recent years:

  • Recommissioning of all HVAC equipment, which included operational testing and inspection. Repairs and corrective action was taken to ensure systems are operating as per their design intent.
  • Increases in the ventilation rates (within limitations of the HVAC equipment)
  • Increase in air filtration levels in HVAC equipment
  • Installation of CO2 monitoring equipment in all schools.
  • Supplemental air filtration units installed in areas with limited ventilation 

With these measures in place we meet and in most cases, exceed the requirements of the current Ventilation and Indoor Air Quality standards published by ASHRAE and other organizations.

Additional measures implemented during the pandemic that remain in place include the deployment of 4000+ portable HEPA filtration units throughout the District. These units are located in all common areas of the schools and in most classrooms. The directives from The Ministry do not require a HEPA filtration unit in all classrooms (provided other measures are in place), however, additional HEPA units are available for any classroom that currently does not have one, upon request.

Standards and Guidelines followed during the pandemic include:

  • ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality
  • ASHRAE Guideline - Epidemic Task Force for the Reopening of Schools.
  • ASHRAE Journal – June 2021 Managing Aerosols Using Space Flushing
  • SickKids (Ontario Science Table) – Covid-19: Guidance for School Reopening.
  • Operational Guidance from The Ministry of Education (August 2021)
  • PHAC & OPH published guidelines for the reopening of building

The increased focus on IAQ during the pandemic has resulted in new industry standards and new guidance from the public health organizations. ASHRAE has recently published a new standard 241-2023 ‘Control of Infectious Aerosols’. This standard builds on the lessons learned during the pandemic and offers more permanent measures to address this issue. The standard is based on a concept of having a ventilation standard to follow during normal conditions (ASHRAE 62.1), and having a secondary standard for higher risk situations. While not expected to be adopted as code for 2-3 years, being proactive, the OCDSB is in the process of implementing measures to comply with this newly-published standard. 

School Specific Information

The Ministry of Education has created a Standardized School Ventilation Measures Report (Excel file), which provides a snapshot of school ventilation and filtration measures taken at each school during the pandemic (last updated in September 2023).

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