Outdoor air is something we often consider overrated. We stay inside, living our lives from the comfort of our homes and never realizing that we are missing out on one of the greatest health benefits in the world, fresh air. Often referred to as the ‘Open Air Factor’, or OAF, fresh air has been known to inactivate viruses and bacteria.
In recent history OAF has been used as the standard treatment of tuberculosis and other such bacterial infections. But its healing properties in relation to tuberculosis have been known since Pliny the Elder (AD 23-79) recommended that people with tuberculosis breathe in the air of evergreen forests, which happens to be high in ozone which is a known germicidal agent.
During the 1960s, scientists working on biodefense research originally coined the term “open air factor,” or OAF, to describe the germicidal component found in outdoor air that could kill pathogens and reduce their infectivity. Interest in the use of open air to promote health and reduce infectious disease fell away in the 1970s and has remained largely ignored since.
The thing is OAF is not new, it has been used as mentioned since the early ADs and was even used by military surgeons during WWI to disinfect and heal severe wounds among injured soldiers.
But it was further put to the test during the influenza pandemic of 1918-19, where it was common to place the sick outside in tents or open-air hospitals. Records from an open-air hospital in Boston during the Spanish Flu outbreak of 1918-19 suggest that these patients and staff were spared the worst of the outbreak.
William A. Brooks, the surgeon general of the Massachusetts State Guard, reported that in a typical general hospital with 76 influenza cases, 20 patients died in a three-day period while 17 nurses became ill. “By contrast,” the researchers wrote, “according to one estimate, the regimen adopted at the camp reduced the fatality of hospital cases from 40% to about 13%.” Which means that it dropped from 30 deaths to 10 by using an open-air hospital.
In the case of a future pandemic, they noted, that better air-handling units and portable filtration units may be warranted for hospitals and other buildings but, even better, “more might be gained by introducing high levels of natural ventilation or, indeed, by encouraging the public to spend as much time outdoors as possible.”
There are multiple factors that reduce infection risk in outdoor spaces. Infectious particles are more rapidly diluted and dispersed, for starters, while temperature and humidity variations could inactivate viruses. Ultraviolet light from the sun is also known to inactivate viruses like influenza and coronaviruses, not to mention that sunlight would have boosted patients’ vitamin D levels, a deficiency of which may increase susceptibility to influenza and other respiratory infections.
The direct germicidal properties of outdoor air have, in recent years, been blatantly overlooked. Experiments done in 1968 revealed that outdoor air was more lethal to airborne pathogens than indoor air.
“Tests were initially carried out during the hours of darkness as, in common with other bacteria and viruses, E. coli are rapidly killed by sunlight. The E. coli samples exposed to outside air usually died off rapidly, but not so indoors.
On some occasions, the E. coli samples in free air lost viability in 30 minutes, whereas those in enclosed air survived for several hours. The bactericidal effect varied from night to night, and it disappeared rapidly in any form of enclosure.”
In addition to E. Coli it was discovered that outside air was also effective against viruses and other bacteria. The germicidal component of the air was dubbed as the OAF, but the researchers were unable to identify what exactly it was composed of. In the 1970s, other researchers determined that OAF was not a single compound but rather “a mixture of highly reactive chemical species which varied in composition.”
When the study was revisited in 2021 scientists could still not pinpoint the exact components. The ongoing mystery of how OAF works may be the reason it continues to be neglected in public health and infection control, although the fact that fresh air is free and unpatentable is likely another factor.
The research into OAF in the 1960s also found that the germicidal effects of outdoor air could be preserved in indoor simulations if ventilation rates had 30 to 36 air changes per hour. Research into older pre-1950s hospital wards used by tuberculosis patients — which had many large windows and tall ceilings — suggest that they had ventilation rates of 40 air changes per hour — and lower tuberculosis infection rates compared to more modern hospitals. The reality is that modern-day hospitals recirculate the same air and are super spreaders of disease.
Yet, the importance of proper ventilation is still largely ignored, even as a study by the U.S. Centers for Disease Control and Prevention found that improved ventilation, such as an open window, reduced COVID-19 cases in Georgia schools more so than mask mandates for staff and teachers.
Decades ago, hospitals and other building types were designed to prevent disease spread, meaning high levels of natural ventilation were a requirement.
Today they’re not. Buildings are no longer designed with natural ventilation in mind, windows are smaller, ceilings lower, and verandas and decks are not as common.
With all this in mind the best way you can look out for your own health is to take control of the OAF. Spend as much time outside as possible and enjoy the fresh air and the germ fighting properties it possesses.