Studies on Air Quality

Why it will take re-engineering, not just medicine, to close the door on COVID.

Understand why adequate indoor ventilation is important in reducing COVID-19 & poorly ventilated indoor spaces can lead to increased levels of transmission.

An Italian study published on Tuesday suggests that efficient ventilation systems can reduce the transmission of COVID-19 in schools by more than 80%.

Nature - An inexpensive type of portable filter efficiently screened SARS-CoV-2 and other disease-causing organisms from hospital air.

Open windows and a good heating, ventilation, and air conditioning (HVAC) system are starting points for keeping classrooms safe during the Covid-19 pandemic. But they are not the last word, according to a new study from researchers at MIT. The study shows how specific classroom configurations may affect air quality and necessitate additional measures, beyond […]

#COVIDisAirborne. If you know how it spreads, you know how to stop it.

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Many schools have not invested in upgrading their air quality. Here's what you should know.

A simple change in the direction of the air forced through indoor gathering spaces by heating, air conditioning, and ventilation systems, could reduce the spread of infectious diseases like COVID-19.

All pandemic long, scientists brawled over how the virus spreads. Droplets! No, aerosols! At the heart of the fight was a teensy error with huge consequences.

Some public venues may need better ventilation to prevent the spread of covid-19 following growing evidence of airborne transmission of the disease, in The BMJ.

Official recommendations lagged behind the science for months.

The benefits of ventilation reach far beyond the coronavirus. What if we stop taking colds and flus for granted, too?

Actions that communities can take to slow the spread of COVID-19.

By Dr. Alondra Nelson, head of the White House Office of Science and Technology Policy and Deputy Assistant to the President The most common way COVID-19 is transmitted from one person to another is through tiny airborne particles of the virus hanging in indoor air for minutes or hours after an infected person has been…

Made from everyday items found in hardware stores, the Corsi-Rosenthal box is a testament to the power of grassroots innovation

Improving air management can help fight Covid-19

Nature - Devices that use wavelengths of sanitizing ultraviolet light that are safe for people could become a more common sight.

This Viewpoint discusses incorporating indoor air ventilation, filtration, and disinfection measures as part of community-level SARS-CoV-2 transmission reduction efforts.

Air filtration serves to reduce concentrations of particles in indoor environments. Most standalone, also referred to as portable or in-room, air filtration systems use HEPA filters, and cost generally scales with the clean air delivery rate. A “do-it-yourself” lower-cost alternative, known as the Corsi-Rosenthal Box, that uses MERV-13 filters coupled with a box fan has been recently proposed, but lacks systematic performance characterization. We have characterized the performance of a five-panel Corsi-Rosenthal air filter. Measurements of size-resolved and overall decay rates of aerosol particles larger than 0.5 microns emitted into rooms of varying size with and without the air filter allowed for determination of the apparent clean air delivery rate—both as a function of size and integrated across particle sizes. The measurements made in the different rooms produced similar results, demonstrating the robustness of the method used. The size-integrated apparent clean air delivery rate increases with fan speed, from about 600 to 850 ft3 min−1 (1019 to 1444 m3 h−1). Overall, our results demonstrate that the Corsi-Rosenthal filter efficiently reduces suspended particle concentrations in indoor environments. One Sentence Summary A DIY air cleaner can effectively reduce aerosols in indoor spaces. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors

This JAMA Insights review summarizes basic measures of indoor air ventilation as a means to explain how increases in frequency of air exchange and filtration capture efficiency could mitigate far-field airborne transmission of SARS-CoV-2 inside rooms and buildings.

Aerosol transmission has been a pathway for the spread of many viruses. Similarly, emerging evidence has determined aerosol transmission for Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) and the resulting COVID-19 pandemic to be significant. As such, data regarding the effect of Heating, Ventilation, and Air Conditioning (HVAC) features to control and mitigate virus transmission is essential. A systematic review was conducted to identify and comprehensively synthesize research examining the effectiveness of ventilation for mitigating transmission of coronaviruses. A comprehensive search was conducted in Ovid MEDLINE, Compendex, Web of Science Core to January 2021. Study selection, data extraction, and risk of bias assessments were performed by two authors. Evidence tables were developed and results were described narratively. Results from 32 relevant studies showed that: increased ventilation rate was associated with decreased transmission, transmission probability/risk, infection probability/risk, droplet persistence, virus concentration, and increased virus removal and virus particle removal efficiency; increased ventilation rate decreased risk at longer exposure times; some ventilation was better than no ventilation; airflow patterns affected transmission; ventilation feature (e.g., supply/exhaust, fans) placement influenced particle distribution. Few studies provided specific quantitative ventilation parameters suggesting a significant gap in current research. Adapting HVAC ventilation systems to mitigate virus transmission is not a one-solution-fits-all approach. Changing ventilation rate or using mixing ventilation is not always the only way to mitigate and control viruses. Practitioners need to consider occupancy, ventilation feature (supply/exhaust and fans) placement, and exposure time in conjunction with both ventilation rates and airflow patterns. Some recommendations based on quantitative data were made for specific scenarios (e.g., using air change rate of 9 h-1 for a hospital ward). Other recommendations included using or increasing ventilation, introducing fresh air, using maximum supply rates, avoiding poorly ventilated spaces, assessing fan placement and potentially increasing ventilation locations, and employing ventilation testing and air balancing checks. Trial registration: PROSPERO 2020 CRD42020193968.

Nature - Risks shoot up when virus particles accumulate in buildings, but it’s not clear how best to improve ventilation.