Ventilation Resources and Information

PN95 Website Visual - Ventilation

Project N95 is dedicated to providing useful information and resources regarding the COVID-19 pandemic. Proper ventilation is one way to protect you and others from the spread of COVID-19.

Improving Ventilation

Many of us spend substantial amounts of time inside. With mask mandates being dropped around the world, there is an increased need to focus on improving indoor air quality. Through proper indoor ventilation, we can reduce the spread of COVID-19 and other respiratory illnesses.

Learn More About Ventilation

See these helpful resources for more information about the importance of ventilation to mitigate the spread of COVID-19.

  • CleanAirCrew.Org Airborne pandemic tips and tools. Disclaimer: This is a collection of resources from experts in their fields. We cannot guarantee the accuracy of all information presented or linked here, especially as conditions are always changing.
  • OSTP Blog "Let's Clear The Air on COVID March 23, 2022, By Dr. Alondra Nelson, head of the White House Office of Science and Technology Policy and Deputy Assistant to the President
  • EPA Guidance on Ventilation The Clean Air in Buildings Challenge highlights a range of recommendations and resources available for improving ventilation and indoor air quality, which can help to protect the health of building occupants and reduce the risk of COVID-19 spread.
  • "Ventilation in Buildings" to advance thought leadership and policy recommendations.

Project N95's Tips to Ventilate Your Space

Air Purifier

Turn on an air purifier that provides the appropriate air flow for your space. Be sure to set the air purifier on its highest setting to ensure that you are getting the full benefits of the product. You can calculate the clean air delivery rate (CADR) for your space using this tool from Harvard.

DIY Air Purifier

Make a DIY air purifier—often known as a Corsi-Rosenthal box or SAFEbox—if you do not have an air purifier readily available to you. These DIY options can be cheaper than a traditional air purifier but require some assembly.

HVAC / Central Air System
  • Running your HVAC or central air system throughout your home can act as a key layer of protection when people are visiting.
  • Turn the "Fan" setting for your HVAC system to "ON" instead of "AUTO" because HVAC systems that filter air do so only when the fan is running.
  • Replace the filters in your HVAC system when they begin to gray or at the recommended intervals specified in your system manual.
  • Consider upgrading your air filters to a MERV-13 or higher rating. Most residential HVAC systems use a MERV-8 as default. It is very important that you check your HVAC manual or speak with an HVAC professional prior to upgrading your filters, however, because your system may not be able to handle filters with different ratings.
Fresh Air

Open two or more windows if it is not too cold outside. Windows that are open even just a few inches will help ensure that air is flowing and improve ventilation.

Interactive Ventilation Tool

We also recommend that you use this interactive ventilation tool from the CDC, which illustrates how different layers of ventilation can reduce the risk of transmission in your home.

Reuters - Italian study shows ventilation can cut school COVID cases by 82% [PHOTO]

Italian study shows ventilation can cut school COVID cases by 82%

Reuters March 22, 2022

ROME, March 22 (Reuters) - An Italian study published on Tuesday suggests that efficient ventilation systems can reduce the transmission of COVID-19 in schools by more than 80%.

An experiment overseen by the Hume foundation think-tank compared coronavirus contagion in 10,441 classrooms in Italy's central Marche region.

COVID infections were steeply lower in the 316 classrooms that had mechanical ventilation systems, with the reduction in cases more marked according to the strength of the systems.

With applications guaranteeing a complete replacement of the air in a classroom 2.4 times in an hour, infections were reduced by 40%. They were lowered by 66.8% with four air replacements per hour and by 82.5% with six air replacements, the study showed.

Most of Italy's schools lack mechanical ventilation systems. Instead, teachers are urged to keep windows open when weather conditions permit.

If the most efficient systems were installed "we could pass from 250 cases per 100,000 students (the alert level set by the education ministry) to a rate of 50 per 100,000," the Hume foundation and the Marche regional government said in its press release.

Smithsonian Mag 03.07.2022 corsi rosenthal box

The Homemade Air Purifier That’s Been Saving Lives During the Covid-19 Pandemic

Smithsonian Magazine By Douglas Hannah, The Conversation March 7, 2022

Portable air filters are an option for augmenting ventilation systems, but they typically cost hundreds of dollars, which puts them out of range for schools and other public spaces that face budget constraints.

This is where the Corsi-Rosenthal box comes in. It’s a cube consisting of four to five off-the-shelf furnace filters topped by a standard box fan blowing outward. Once sealed together with tape, it can sit on a floor, shelf or table. The fan draws air through the sides of the cube and out the top. The units are simple, durable and easy to make, and are more effective than simply placing a single filter in front of a box fan. It usually takes 40 minutes, minimal technical expertise and $60 to $90 in materials that are available from any home supply store.

Sci Am 06.08.22 "We need to Improve Indoor Air Quality" Photo

We Need to Improve Indoor Air Quality: Here’s How and Why

Scientific American - By Tanya Lewis June 8, 2022

More than a century ago, pioneering nurse and statistician Florence Nightingale proclaimed the importance of open air and bedroom ventilation for tuberculosis patients. Today in Nordic countries, it is common practice to let babies nap outside, sometimes in freezing temperatures. But even though humans have long attributed health benefits to fresh outdoor air, it is a lesson many of us seemed to have largely forgotten—until the COVID-19 pandemic forced us to relearn it.

It is now widely acknowledged that SARS-CoV-2, the virus that causes COVID, is frequently transmitted by airborne droplets called aerosols that hang in the air and can travel over short and long distances. “This is a virus that spreads through the air almost exclusively indoors. If we start there, then the building matters,” says Joseph Allen, an associate professor at the Harvard T. H. Chan School of Public Health and director of its Healthy Buildings program. ... ASHRAE standards aim to limit exposure to harmful substances with known exposure limits, such as formaldehyde and other volatile organic compounds, but not to pathogens—for which there are far fewer data—according to William P. Bahnfleth, chair of the ASHRAE Epidemic Task Force and a professor of architectural engineering at Pennsylvania State University. “Current minimum ventilation rates—alone—do not provide complete mitigation of airborne disease transmission risk,” Bahnfleth wrote in an e-mail to Scientific American. He added that although transmission risk cannot be reduced to zero, combining precautions such as vaccination, mask use and occupancy limits with engineering practices, including ventilation, filtration and air disinfection, “is the most effective way to minimize risk.”

Assessing impact of ventilation on airborne transmission of SARS-CoV-2

Assessing impact of ventilation on airborne transmission of SARS-CoV-2: a cross-sectional analysis of naturally ventilated healthcare settings in Bangladesh

BMJ Open - By Ashley Styczynski, Caitlin Hemlock, Kazi Injamamul Hoque, Renu Verma, Chris LeBoa, Md. Omar Faruk Bhuiyan,Auddithio Nag, Md. Golam Dostogir Harun, Mohammed Badrul Amin, Jason R Andrews April 15, 2022


COVID-19 remains an ongoing threat to populations around the world. As with outbreaks of other emerging infectious diseases,67–69 healthcare facilities were a source of transmission in the early spread of SARS-CoV-2, resulting in an excess of healthcare worker infections.1 20 Improving the safety and resiliency of healthcare facilities is imperative for protecting against future epidemic spread. This is only possible by adequately equipping healthcare spaces with durable mitigation measures that are effective against a range of transmission patterns. While the COVID-19 pandemic will eventually subside, the risk of airborne transmission of other diseases remains a substantial risk in healthcare facilities with inadequate ventilation. Now is the critical moment of action to prevent healthcare facilities from further amplifying the current and future pandemics.

Johns Hopkins School Ventilation: A Vital Tool PDF image

School Ventilation: A Vital Tool to Reduce COVID-19 Spread

The Johns Hopkins Center for Health Security - By Paula J. Olsiewski, Richard Bruns, Gigi Kwik Gronvall, William P. Bahnfleth, Gunnar Mattson, Christina Potter, Rachel A. Vahey May 26, 2021

In this report, we consider the impact of the COVID-19 pandemic on children, families, and educators; review the evidence that improvements in ventilation reduces risks of disease transmission; and summarize current ventilation guidelines. While ventilation improvements may often be perceived as a complicated and expensive investment, we demonstrate in a cost-effectiveness analysis comparing ventilation with enhanced (“deep”) cleaning that ventilation improvements are a cost-effective public health measure. As new, potentially more transmissible variants of SARS-CoV-2 continue to emerge, broad improvements in indoor air quality are important for reducing transmission. Improvements to ventilation are a good use of the COVID-19 relief funds provided to K-12 schools.

To produce this report and recommendations, we interviewed 32 experts in air quality, engineering, education policy, and communications, as well as teachers at schools that have been open for in-person learning during the pandemic. We examined relevant peer-reviewed scientific literature and engineering best practices for indoor air quality as well as specific guidance for K-12 schools issued by the CDC and expert industry organizations. We also hosted a webinar featuring experts in indoor air quality, engineering, and schools to highlight their expertise and provide recommendations for what can be done now to reduce SARS-CoV-2 transmission through improvements in ventilation and to add to the mitigation measures that schools are already taking.

Science Direct Logo

Are the Portable Air Cleaners (PAC) really effective to terminate airborne SARS-CoV-2?

The Johns Hopkins Center for Health Security - By María Rodríguez, M. LlanosPalop, Susana Seseña, & Ana Rodríguez Sept 1, 2021

Abstract The transmission of SARS-CoV-2 virus through aerosols has become an outstanding issue, where plenty of spread aspects are being analyzed. Portable Air Cleaners (PAC) with high-efficiency particulate air (HEPA) filters have been discussed as an adjunctive means for indoor environments coronavirus decontamination. This study evaluates, first, the air and surfaces SARS-COV-2 RNA contamination due to positive patients in households, and second, the efficiency of a PAC with HEPA filter to eliminate virus. A total of 29 air and surface samples were collected inside 9 households, by using an air portable collector with gelatin filters and swabs. SARS-CoV-2 RNA detection was performed using real-time reverse transcription polymerase chain reaction (RT-PCR). Overall, all the air samples collected before using PAC and 75% of swab samples were positive for SARS-CoV-2. After the PAC usage, all samples except one were negative, displaying a 80% device effectiveness. Portable HEPA cleaners usage allowed the removal of SARS CoV-2 and, therefore, they could be recommended for places with inadequate ventilation, considering the limitations and functionality of the device.


Are the Portable Air Cleaners (PAC) really effective to terminate airborne SARS-CoV-2? really effective to terminate airborne SARS-CoV-2? - Info Blurb")

The Johns Hopkins Center for Health Security - By Gerhard K. Rencken, Emma K. Rutherford, Nikhilesh Ghanta, John Kongoletos, and Leon Glicksman July, 2021

3.3.2. Simulation C: baffles on double hung windows aligned with rows of students Another possible way to avoid strong horizontal air currents interacting with exhaled air would be to place a baffle inside the windows that directs the air downwards. We simulated this by maintaining the same mass flow rate but directing the incoming air from the windows downwards at a 45° angle. In Simulation C, the windows are again aligned with the rows of students as in Simulation A.

Compared with the results of Simulation A, where the air entered the room normal to the windows, the CO concentration at the breathing planes is lower for Simulation C, where the air from the windows is directed downwards. A cool layer of air near the floor seems to create a strong buoyancy effect so that most of the infected aerosols rise and are suspended above breathing level until they exit the room through the outlet windows. This starts to approach displacement ventilation although the air entering the room in this case has a high momentum causing recirculation and higher aerosol concentration at breathing level. These results suggest that baffles to direct air downwards could be an effective measure in classrooms with windows spanning an entire wall where the staggered alignment of Simulation B is not possible.

22 330260-A Swardstrom School ventilation tool graphics obj gauge 100

CDC: Ventilation in Schools and Childcare Programs

How to use CDC building recommendations in your setting

Ventilation is one component of maintaining healthy environments, and is an important COVID-19 prevention strategy for schools and childcare programs. Wearing a well-fitting, multi-layer mask helps prevent virus particles from entering the air or being breathed in by the person wearing a mask. Good ventilation is another step that can reduce the number of virus particles in the air. Along with other preventive actions, ventilation can reduce the likelihood of spreading disease.

Saliva Direct

Yale School of Public Health - SalivaDirect™ - Ventilation

Yale School of Public Health

COVID-19 is an airborne disease - so the better your ventilation, the lower your risk.

Resources, research, guides, & links to other useful information for individuals, school administrators, & building managers on how to leverage Ventilation as a tool to mitigate the spread of COVID-19 in enclosed spaces.