Solid Science Practical Solutions


Covid-19 and Ventilation in Schools

An Important Tool to Improve Ventilation for Safe
Re-Opening of Schools in 2021
OSHA and the CDC’s key mitigation strategies are essential to the safe delivery of in-person instruction and to mitigate SARS-CoV-2 (COVID-19) virus transmission in schools: 
Unfortunately, these guidelines for improvements in ventilation systems are general in nature whereas school buildings and district-specific conditions must be individually evaluated for maximum effectiveness. 
Ventilation improvements may include some or all of the following general approaches:
  • Increase outdoor fresh air and air movement via adjustments to air intakes, strategically placed fans and open windows.
  • Ensure ventilation systems operate properly and provide acceptable indoor air quality for the current occupancy level for each space.
  • Turn off any demand-controlled ventilation (DCV) controls to keep fans running continuously.
  • Improve central and local air filtration.
  • Ensure restroom exhaust fans are functional and operating at full capacity when the building is occupied.
  • Inspect and maintain local exhaust ventilation in areas such as kitchens and science labs, etc. Operate these systems any time these spaces are occupied.
  • Consider portable high-efficiency particulate air (HEPA) filtration systems to help enhance air cleaning especially in higher risk areas. (High-risk areas include highly occupied, confined, and smaller interior spaces with limited options for ventilation.)
  • Consider using ultraviolet germicidal irradiation (UVGI) as a supplement to help inactivate the SARS-CoV-2 virus, especially if options for increasing room ventilation are limited. 
  • Consider running the heating, ventilation and air conditioning (HVAC) system at maximum outside air intake for 2 hours before and after the building is occupied
While these general recommendations can provide a useful framework for helping to prevent virus transmission, their value is limited if they are not adapted to individual school building conditions. 
Without certain scientific data, it is difficult to know where the highest risk areas are and how to design and implement improvements where they are needed most to get maximum value for your investment.
Carbon Dioxide (CO2) Levels as a Benchmark for Covid-19 Risk
The February 2021 report by the Environmental Resource Council presents the case for using CO2 concentrations indoors and outdoors to assess the risk of SARS-CoV-2 virus transmission. The full report can be found at:
Key Findings and Recommendations:
  1. Given that we now understand that airborne aerosols in shared air are the primary source of transmission of the SARS-CoV-2 virus, an increased focus on ventilation is essential.
  2. This is a particular concern in schools with traditionally dense occupancy and often limited air exchange. Also, the construction of older school buildings did not have the modern HVAC systems and technology necessary to minimize the risk of airborne transmission of viruses and other infectious agents.
  3. In 1996 the EPA tested 41 buildings and detected a direct correlation between virus-based disease rates and “dCO2”, (the difference between outside air and inside air CO2 concentrations). They concluded that indoor CO2 measurements hold promise for mass monitoring of indoor aerosol transmission risk for COVID-19 and other respiratory diseases. Although peer review and expanded research would be helpful and will certainly be forthcoming, it is clear that schools can presently benefit from obtaining low-cost dCO2 data in their schools.
  4. The comparison of CO2 outside and inside of school buildings may serve as a proxy for SARS-CoV-2 exposure and the consequent risk of contracting COVID-19.
  5. With real-time CO2 data, schools can make knowledgeable adjustments regarding distancing, class size, class activity and especially air exchange. The costs associated with implementing this testing protocol are minimal. The execution of the program requires focus and professional understanding of the concepts and technical aspects of dCO2 data collection and interpretation. At some level safety and relative risk of COVID-19 in schools may be numerically calibrated, providing guidance for school administration and reassurance for students, parents, staff and the community.
  6. There would be three (3) major goals to this testing procedure:
  • To quantify the relative safety of an individual classroom or area where people may congregate.
  • To develop feedback on the quality of the existing HVAC systems and the effectiveness of other protective procedures.
  • To determine the most cost-effective approach to improving the IAQ in high-risk areas.
If this is executed correctly, there will be real-time feedback and a straightforward process to review the findings and make determinations regarding optimal safety procedures, policies, and mechanical engineering options.
Based on these findings and our in-depth understanding of IAQ and HVAC issues, GSE has developed a unique and targeted program to assist schools in assessing IAQ conditions and developing strategies for improvement. The service includes the following components.
Building HVAC-IAQ Inspections:
GSE will conduct a site survey of each school facility to gather necessary information about the buildings’ construction, configurations, and HVAC systems. We will review such factors as; amount/percentage of fresh air entering the building, presence and effectiveness of ventilation and exhaust (to remove indoor air), sanitary conditions of accessible sections of the systems, configuration of air supplies in regards to airflow in occupied areas, availability of openable windows, etc. 
IAQ Testing and Reporting:
  1. During our inspections, measurements will be taken using a calibrated handheld IAQ Monitor equipped with a four (4) function probe. The primary focus will be on the amount of CO2 inside vs. outside to establish a “dCO2”, (the difference between outside air and inside air CO2 concentrations). However, we will simultaneously measure temperature, relative humidity, and carbon monoxide (CO) to further evaluate the overall IAQ.
  2. In high-risk areas, we may recommend the placement of CO2 monitoring equipment with the capability to record and graphically present multi-day data to further assess CO2 concentrations over time.
  3. Based on field findings, we may also conduct limited smoke testing (with non-toxic smoke) to assess airflow patterns in key areas of the buildings.
  4. GSE will analyze the data and compare to relevant IAQ standards (including NJ PEOSH IAQ regulations and ASHRAE guidelines) to develop written recommendations for HVAC-IAQ improvements. If available, data will be plotted on floor plans to better understand building-wide CO2 levels and HVAC characteristics and expedite effective follow-up planning.