Covid-19 Mitigation: Air Quality, Ventilation and Filtration
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A large HEPA filter cleans the air in an Elizabeth High School classroom.
Elizabeth School District has taken – and will continue to take – several important steps to minimize virus transmission within district school buildings, buses and administrative offices. This page serves as an ongoing resource, as well as an archive, for providing safe environments for teaching and learning.Students' educational needs are best served when they can be present in school, with the fewest possible personal restrictions. The district has been able to safely provide in-person learning consistently since the beginning of the 2020-21 school year, with a minimum of individual requirements. On this page, you will find information behind the steps taken by the district to allow the greatest freedom, and fewest personal constraints, for students and staff.
Data has consistently shown that our schools have not been a vector for community spread of Covid-19. This is the result of a true community partnership because of:
- Parents ensuring sick and Covid-exposed students stay home.
- School staff members maintaining safe practices.
- The availability of rapid, at-home antigen tests for students, families and employees.
- HEPA air purifiers in classrooms.
- Comprehensive building-level air-quality measures.
The supporting documentation below cites experts in air quality, medical science and related fields on the aerosol nature of the virus and the steps to minimize its spread. Since August of 2020, the district has systematically and comprehensively followed the findings of experts and decision makers from around the world to create safe environments for learning that do not require individual action beyond staying at home when sick and voluntary at-home Covid testing. Vaccines and masks are welcomed but not required to maintain a safe educational setting in our schools.
As noted in communications to parents (archived at right), district staff have been measuring air quality in each building since the start of the 2020 school year, while tracking the number of cases in schools focusing on instances of likely or confirmed virus spread within the schools.
The resources below, coupled with the district's data, have shown that we can continue in-person education while containing the spread of Covid-19 without individual mandates.
A carbon dioxide monitor sits on a shelf in an Elizabeth High School office. The monitors are moved to different locations in each school building to measure air quality.
Air Filtration, Ventilation and CO² monitoring steps in Elizabeth School District
- Heating, Ventilation and Air Conditioning (HVAC) Systems.
- MERV 13 level filters installed in all units.
- HVAC programmed to run continuously when the building is occupied.
- HVAC vents adjusted to increase amount of outside air pulled into the system.
- HVAC system monitored, tuned and maintained regularly.
- At least two large, standalone HEPA air purifiers placed in every classroom and all occupied, small- and medium-sized indoor spaces (HEPA air purifiers are not effective in open spaces such as gymnasiums and large cafeterias).
- All spaces monitored for CO² levels within target ranges. More than 1,500 readings have been taken since August 2021. See PDF file of actual readings to date for the 2021-22 school year.
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The photos in the slideshow above represent some of the aspects and systems that are used to exchange outdoor and indoor air. The first few images show one of three units on the roof above the EHS gym. Each unit has mixed-air dampers that are controlled remotely by software. The dampers are opened to certain amounts for specific periods of time each day to allow fresh, outdoor air to replace indoor air. The air flows through 21 industrial-quality MERV 13 air filters in each unit (for a total of 63 above the gym alone) before being pumped into the building’s HVAC system. The next three images show some of the various displays of the building management system that allow staff to both monitor and control the amounts and timing of fresh air pumped into the buildings as well as temperature and operational status for each unit that controls specific parts of the buildings. The final image shows filters and dampers at Singing Hills Elementary School.
Research and Resources
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Below is a collection of dozens of research studies, reports, guiding documents and more that were used to inform choices made in Elizabeth School District. The large body of scientific evidence that the virus which causes Covid-19 primarily travels through the air, and the related studies of ventilation and air filtration, were important factors in the allocation of resources to ensure Elizabeth Schools could remain safely in-person throughout the 2020-21 and 2021-22 school years.
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Academic Research
Video: Build a do-it-yourself air purifier for about $25
Dr. Jeffrey E. Terrell, director of the Michigan Sinus Center, demonstrates in this July 2011 video how to build an air purifier with a HEPA filter for about $25 with parts from a local hardware store. The video gained new interest with the onset of the pandemic.NASA Study: Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials
A 2016 study by NASA has been referenced often during the pandemic by experts calling for greater use of HEPA air filters to improve the quality of indoor air to reduce the spread of coronavirus. (PDF)Air Filters, Pollution and Student Achievement
This March 2020 paper connects student achievement to filtered air and demonstrates that students score higher in math and English when cost-effective measures are taken to improve air quality. (PDF)Small droplet aerosols in poorly ventilated spaces and SARS-CoV-2 transmission
The May 27, 2020, edition of The Lancet Respiratory Medicine details scientists’ measurement of droplets pushed into the air by coughing and sneezing. They measured how long the droplets stayed in the air. Their determination was a greater need for improved ventilation of indoor spaces to reduce the time those droplets stay in the air. (PDF)COVID-19 Airborne Transmission Tool Available
In June 2020, CU-Boulder’s Cooperative Institute for Research in Environmental Science (CIRES) made available its modeling tool for Covid-19 transmission in classrooms, buses, protests and more: COVID-19 Aerosol Transmission EstimatorIt Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19)
A July 2020 article in the medical journal Clinical Infectious Diseases illustrates how microdroplets that can carry disease can be minimized with proper airflow and filtration. (PDF)COVID-19 transmission patterns only seem explainable by aerosols
CU Professor Jose-Luis Jimenez explains in this July 2020 post the science behind transmission of coronavirus via aerosols. Jimenez has been cited as a leading expert in multiple articles. This is his own explanatory webpage. (PDF)Why better ventilation is key to limiting COVID-19 spread on campus
Globally recognized experts from CU-Boulder published an article in August 2020 about the importance of ventilation (outside air, air circulation, air filters) in limiting COVID spread. (PDF)Healthy Buildings
Harvard’s T.H. Chan School of Public Health published its Healthy Buildings guidance in June 2020 and updated it in November 2020 as part of a larger effort called Risk Reduction Strategies for Reopening Schools. The building guidance centered on increasing outdoor air ventilation, filtering indoor air, using portable air cleaners, verifying the performance of those systems and more. (PDF)5-step guide to checking ventilation rates in classrooms
Harvard’s T.H. Chan School of Public Health issued this PowerPoint presentation in November 2020 to offer guidance on measuring the sizes of spaces, air ventilation rates, use of windows, MERV 13 filters, portable air cleaners, mechanical ventilation and more. (PDF)We’re better off when we can breathe easy
As part of Harvard’s “Better Off” podcast series, the Dec. 11, 2020, episode featured healthy-buildings expert Joseph Allen sharing tips to make breathing safer and easier in homes, schools and offices. (PDF of transcript)Carbon dioxide levels reflect COVID-19 risk
An April 2021 article based on CU-Boulder research confirms the value of measuring carbon dioxide to estimate the risk of infection. (PDF)A paradigm shift to combat indoor respiratory infection
The University of Leeds published a paper in May of 2021 calling for airborne infection transmission to be treated with the same level of attention as diseases transmitted through food and water. The authors focus mainly on standards for indoor air ventilation. (PDF)Cleaning indoor air may prevent COVID-19’s spread. But it’s harder than it looks
A May 2021 article cites CU professor Jimenez saying air filters in every classroom would be a better investment than money spent on disinfection of surfaces. (PDF)Breathing, speaking, coughing or sneezing: What drives transmission of SARS-CoV-2?
This June 2021 research published in the Journal of Internal Medicine examines how Covid infections affect people’s upper- and lower-respiratory tracts, noting “The abundance of … speech-generated aerosol, combined with its high viral load in pre- and asymptomatic individuals, strongly implicates airborne transmission of SARS-CoV-2 through speech as the primary contributor to its rapid spread.” (PDF)Localized and Whole-Room Effects of Portable Air Filtration Units on Aerosol Particle Deposition and Concentration in a Classroom Environment
Portable air filtration units may reduce Covid-19 infection risk in indoor spaces where ventilation is limited, according to an August 2021 preprint of a journal article (meaning it has not been peer reviewed by scientists but is ready for review). (PDF)
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Air Quality and Ventilation (CDC, EPA)
Improving Ventilation in Your Home
This January 2021 guide offers illustrations and tips on how to improve air flow in a household to prevent virus particles from accumulating. (PDF)Ventilation in Schools and Childcare Programs
This February 2021 illustrated guide from the CDC shows how opening windows, using portable air cleaners, and improving building-wide filtration can increase ventilation in a school or childcare program. (PDF)Scientific Brief: SARS-CoV-2 Transmission
The May 2021 update from the CDC included an update to reflect current knowledge about SARS-CoV-2 transmission; categorization of the modes of transmission (inhalation, deposition of virus on exposed mucous membranes, and touching mucous membranes with soiled hands contaminated with virus); and prevention measures. (PDF)Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools
In May 2021, the CDC reported results from a study of mitigation efforts taken in Georgia schools, which showed COVID-19 incidence was 37% lower in schools that required teachers and staff members to use masks and 39% lower in schools that improved ventilation. Ventilation strategies associated with lower school incidence included dilution methods alone (35% lower incidence) or in combination with filtration methods (48% lower incidence). (PDF)Ventilation in Buildings
In June 2021, the CDC offered an updated, wide-ranging 24-page guide on the why, what and how to improve building ventilation to slow the spread of Covid-19. (PDF)White House Launches Effort to Improve Ventilation and Reduce Spread of COVID-19 in Buildings
Following up on the Biden Administration's March 2022 release of the National COVID-19 Preparedness Plan to continue fighting the virus while returning the country to normal, a fact sheet was released to explain the Clean Air in Buildings Challenge and other efforts to improve ventilation in school buildings and other indoor spaces. (PDF)Clean Air in Buildings Challenge
In March 2022, the Environmental Protection Agency issued an indoor air quality guide to help building owners and operators reduce risks from airborne viruses and other contaminants indoors. (PDF).
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Covid in Colorado
Letter to Gov. Polis
Elizabeth School District superintendent Douglas Bissonette emailed Gov. Jared Polis on Aug. 12, 2020, to highlight the need to adjust CDPHE guidance on virus transmission for the sake of safely returning to in-person educational instruction.CDPHE Ventilation Guidelines
The Colorado Department of Public Health and Environment produced a 7-page guide on indoor air ventilation in September 2020. (PDF)Air Quality Improvement Grants
The state's Public School Capital Construction Assistance Board is authorized to award grants for purchase of portable high-efficiency particulate air (HEPA) fans or filtration systems for classrooms made on or after April 1, 2021.One Colorado scientist’s uphill fight to convince the world that coronavirus spreads through the air
The Colorado Sun in July of 2021 profiled the work of CU-Boulder professor Jose-Luis Jimenez and his colleagues, noting the impact they made on the global understanding of how Covid-19 spreads. (PDF)6 Questions To Ask Your Colorado School About COVID And The Air In Your Child’s Classroom
In August 2021, Colorado Public Radio reported on efforts to improve ventilation in Colorado schools. Many of the same facts presented on this page regarding the science of indoor air quality are contained in the report. In the accompanying radio story (linked at the top of the CPR page) about what schools are doing, Elizabeth School District was mentioned as a “standout” district regarding ventilation improvement. A supplementary chart shows what 25 Colorado school districts said they were doing for ventilation at the time of the report, including Elizabeth. (PDF)CDPHE Ventilation in Schools: Quick tips and resources
Made available in November 2021, these three pages offer guidance, references and links to other resources to help schools check their systems, improve what’s needed and maintain it. (PDF)Opinion: The air inside Colorado schools needs to be cleaned up
In November 2021, Debra Thomas, acting regional administrator of the Environmental Protection Agency Region 8, wrote an opinion piece for The Colorado Sun citing the example of Colorado Springs District 11, which put $32.68 million in federal and state grant funding to use upgrading HVAC systems in its buildings to impede the spread of Covid-19. (PDF)Here’s where (and how) you are most likely to catch COVID, according to a new CU Boulder study
In January 2022, the CU-Boulder team that has been at the forefront of research into the airborne spread of Covid-19 produced a chart showing a variety of scenarios compared with mitigation strategies as well as the percentage of likelihood of becoming infected. The chart is an extension of the group’s work to create the Covid-19 Aerosol Transmission Estimator. (PDF)
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Major Media Reports
Most COVID-19 Test Boxes Are Wrong: How to Find Your Tests' Real Expiration Dates
This Aug. 2022 article from CNET explains the FDA's extension of expiration dates for COVID-19 tests and includes links to lists of brands, lot numbers and their expiration dates. (PDF)Yes, the Coronavirus Is in the Air
This July 2020 New York Times commentary piece from Linsey C. Marr, professor of civil and environmental engineering at Virginia Tech, provides information about aerosol transmission of Covid and what should be done to prevent its spread. (PDF)What 'airborne coronavirus' means, and how to protect yourself
In August 2020, the work of several air-quality experts began to gain attention as the world sought to understand how coronavirus spreads. This National Geographic article explains the details of virus transmission through the air. (PDF)COVID-19 Is Transmitted Through Aerosols. We Have Enough Evidence, Now It Is Time to Act
In a TIME Magazine article from Aug. 25, 2020, CU professor Jimenez identified the ways Covid-19 spreads and how to reduce the risk of transmission. (PDF)Coronavirus is in the air. Here’s how to get it out.
An August 2020 article from Vox.com, an explanatory journalism service, describes the science behind the spread of coronavirus and how to slow it down with improved air filtration and ventilation. (PDF)Ventilation should be part of the conversation on school reopening. Why isn’t it?
In her August 2020 opinion piece on STAT, a medical and health news service, epidemiologist Alexandra Feathers provided a real-world look at the status of ventilation in buildings, linking to research showing how much of a difference proper ventilation could make in battling Covid-19. (PDF)Advice on Airborne Virus Transmission Vanishes From C.D.C. Website
The New York Times reported in Sept. 2020 that the Centers for Disease Control and Prevention had published new guidance on airborne transmission of the virus only to pull it, saying it was “posted in error.” The Times documents some of the arguments in the scientific community about droplet transmission vs. aerosol transmission. (PDF)Scientists say the coronavirus is airborne. Here’s what that means.
An October 2020 article on Vox.com describes the science behind aerosols, droplets and the spread of Covid-19. (PDF)The 60-Year-Old Scientific Screwup That Helped Covid Kill
In May 2021, WIRED Magazine reported on a small group of scientists whose detective work revealed researchers’ errors from the 1930s, ’40s and ’50s on the measurement of droplet sizes. The scientists, including Linsey Marr and Jose-Luis Jimenez — mentioned multiple times elsewhere in this list of resources – were able to offer corrections to the accepted science and improve on efforts to reduce Covid’s spread. (PDF)The Coronavirus Is Airborne Indoors. Why Are We Still Scrubbing Surfaces?
The New York Times in June 2021 said scientists who initially warned about contaminated surfaces now say that the virus spreads primarily through inhaled droplets, and that there is little to no evidence that deep cleaning mitigates the threat indoors. (PDF)The Plan to Stop Every Respiratory Virus at Once
In September 2021, The Atlantic magazine published a report on the benefits of ventilation not only for combatting Covid-19 but also for standard colds and flus. “If we are to live with this coronavirus forever — as seems very likely — some scientists are now pushing to reimagine building ventilation and clean up indoor air. We don’t drink contaminated water. Why do we tolerate breathing contaminated air?" (PDF)239 Experts With One Big Claim: The Coronavirus Is Airborne
In October 2021, The New York Times reported that the World Health Organization was resisting mounting evidence that viral particles that float in indoor air are infectious, as 239 scientists had claimed. Despite their evidence, the WHO maintained at the time that the research was still inconclusive. (PDF)The Hot New Back-to-School Accessory? An Air Quality Monitor.
In October 2021, The New York Times shared information on personal use of air quality monitors by families. Based on information from a University of Denver professor, parents were sending their children to school with the monitors in their backpacks or pockets. At the time of publication, Elizabeth School District had been using such monitors as common practice in each school for several months. (PDF)Italian study shows ventilation can cut school Covid cases by 82%
In March 2022, US News & World Report shared a Reuters account about a study in Italy measuring coronavirus spread in 10,441 classrooms. It showed that the 316 classrooms with mechanical ventilation systems had significantly lower numbers of Covid infections. The study went further by testing the numbers of times per hour that classroom air was fully replaced by ventilation, and those with six replacements per hour had an 82.5% reduction in infections. (PDF)This invisible Covid-19 mitigation measure is finally getting the attention it deserves
This April 2022 article and accompanying video from CNN notes that ventilation is “one of the most powerful tools against coronavirus” and is beginning to receive the attention it deserves. The piece quotes air-quality experts and a New Hampshire school superintendent, who said ventilation is “something that most in the building don't think about, but it's a very passive way for us to create safety within the schools. Since the beginning, the goal was always 'let's get our kids in, let's get our staff in, but let's do it in a way that's safe for all of them.'"
According to Max Sherman, a leader on the Epidemic Task Force for the American Society of Heating, Refrigerating and Air-Conditioning Engineers, “Good ventilation isn't only about keeping students safe from Covid-19. It can also improve their performance in school.” (PDF)
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International Resources
Canada - COVID-19 spreads through the air. Here's what you can do about it this winter
In November 2021, this Canadian Broadcasting Corporation report said the Public Health Agency of Canada had updated its recommendations for opening windows to increase ventilation and using HEPA filters to clean indoor air, but it stopped short of advocating for better-quality masks or saying outright that the virus is primarily airborne. (PDF)Canada - COVID-19: Improving indoor ventilation
The Canadian government compiled a list of measures that can be taken to improve indoor air quality. (PDF)Canada - At home: Using ventilation and filtration to reduce the risk of aerosol transmission of COVID-19
The Canadian government also compiled recommendations to improve the overall air quality in the home, as well as help reduce the risk of aerosol transmission of COVID-19 by reducing the number of viruses suspended in the air. (PDF)Canada - COVID-19: Guidance on indoor ventilation during the pandemic
Canada’s Public Health Agency of Canada developed a guide to inform Canadians about how indoor ventilation, in combination with other recommended public health measures, can reduce the spread of COVID-19. The guide also provides practical tips on how to improve indoor air, ventilation and filtration to help reduce the spread of COVID-19. (PDF)New Zealand - Coronavirus Covid-19: Better ventilation 'absolutely critical' to stopping Delta
In August 2021, experts warned against the use of “isolation hotels” for those infected with Covid-19 and demonstrated how aerosolized virus particles spread in such places if they have inadequate ventilation. (PDF)New Zealand - Covid 19 Delta outbreak: Lack of air filtration systems in MIQ facilities - public health expert
In September 2021, as New Zealand was facing difficulties due to the Delta variant of Covid-19, the country’s quarantine plans were criticized because special facilities did not all have adequate ventilation. Within the New Zealand Herald’s story about the controversy is information from researchers about the value of HEPA filters. (PDF)New Zealand - Covid 19 Delta outbreak: Classroom air quality an 'incredible blindspot', researcher says
An October 2021 report from the New Zealand Herald said that in the country with strict Covid-mitigation measures (shown in infographics on the webpage), “Half of classrooms in a 2013 Auckland study found ‘very poor’ ventilation by measuring carbon dioxide levels.” (PDF)New Zealand - Covid 19 Delta outbreak: Ministry of Education ordering air purifiers, CO2 monitors for schools
In December 2021, New Zealand’s Ministry of Education announced its remediation plans for classrooms after a November report said one in five schools was not meeting standards. (PDF)Spain - Spanish scientists demand ‘urgent’ action to curb airborne transmission of coronavirus
In March 2021, the newspaper EL PAÍS said more than 100 health professionals urged Spain’s central and regional authorities to take steps to prevent aerosol infection in poorly ventilated indoor settings. (PDF)Spain - Avoiding coronavirus infection in indoor spaces: don’t breathe other people’s air
Also in March 2021, EL PAÍS published animated graphics and a story explaining that “constant ventilation and permanent control of CO₂ levels are two of the keys to avoiding transmission in closed rooms, as fresh air dilutes the infected particles.” (PDF)UK - Role of ventilation in controlling SARS-CoV-2 transmission
The United Kingdom’s Environmental and Modelling Group published a document in September 2020 to provide guidance across the UK for ventilation and Covid mitigation, including ways to improve air flow and increase distance between people in certain circumstances, as well as measuring carbon dioxide to identify spaces that need ventilation improvements. (PDF)UK - New film shows importance of ventilation to reduce spread of COVID-19
A short video released by the UK government in November 2020 shows how coronavirus lingers in enclosed spaces, and how to keep your home ventilated. (PDF)UK - Covid: classrooms in England to get CO2 monitors to help with ventilation
In August of 2021, the secretary of education at the time announced that all classrooms in England would be outfitted with carbon dioxide monitors in an effort to improve ventilation in state schools and colleges. (PDF)
Previous Messages to Parents
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Larry Lorimer, head custodian at Elizabeth High School, checks the status of industrial-grade MERV 13 filters on one of 26 rooftop units at EHS. Multiple filters are used in each unit.
ESSER III Use of Funds Plan
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The publishing of the following notice is required by the Colorado Department of Education for Elementary and Secondary School Emergency Relief (ESSER III) funding, which is the state-level administration of federal American Rescue Plan funds.
Elizabeth School District
ESSER III – Use of Funds PlanUnder this multi-year grant, the district has until September 30, 2024, to spend ESSER III funds. As priorities change in responding to COVID-19 and its effect on students and staff, the use of funds plan may be revised.
As of January 2022, ESSER III funds will be used to address the four main areas of focus as follows:
- Academic Learning Loss
- Extend and enhance summer school offerings
- Inscreas after-school tutoring
- Purchase instruction and assessment materials
- Mental Health Supports
- Add behavior support specialists
- Purchase assessment materials
- Add counseling support
- Health and Safety Needs
- Improve air quality and ventilation by replacing HVAC units
- Continuity of Operations
- Increase substitute pay for teachers and support staff