Maintaining relative humidity in the 40%-60% range in indoor spaces could help slow the spread of the coronavirus this winter, according to a November 18, 2020 Washington Post opinion piece co-authored by Joseph Allen, associate professor of exposure assessment science and director of the Healthy Buildings program at Harvard T.H. Chan School of Public Health.
The authors explained that humidity can affect virus transmission in three ways. Studies suggest that higher humidity can enhance the body’s ability to fight off infection; that the coronavirus decays faster at close to 60% relative humidity than at other levels; and that drier air can lead to greater numbers of tiny coronavirus particles that travel farther and penetrate deeper into the lungs.
“A level of 40 to 60 percent is right in the sweet spot where we get the benefits of some humidity but not the drawbacks of too much,” according to the authors.
They noted that portable humidifiers can easily increase the relative humidity in homes, where coronavirus transmission frequently occurs. “As winter sets in, we need to defend our home, schools and offices,” the authors wrote. “In addition to other strategies—masks, distancing, ventilation and filtration—raising the humidity is another layer of defense to consider.”
Read the Washington Post op-ed: This winter, fight covid-19 with humidity