Health Advice



How better ventilation can help 'COVID-proof' your home

Liz Szabo, Kaiser Health News on

Published in Health & Fitness

For extra protection, place a box fan in the patient’s window, facing outward, to draw germy air outside. Seal any openings around the sides of the fan, said Jim Rosenthal, CEO of Tex-Air Filters, a company that manufactures air filtration products in Fort Worth, Texas.

“It’s real simple, and it’s cheap,” Rosenthal said.

To prevent infected air from seeping out of the sickroom, Fox suggests wedging towels in the gap under the bedroom door. People should also cover return air grills with plastic. These grills cover vents that suck air out of the room and recycle it through the heating or cooling system.

Fox also suggests turning on bathroom or kitchen exhaust fans, which can shuttle germy air outside. Although running exhaust fans while taking a shower is relatively safe, Fox said, it’s important to open windows when running the fans for more than 10 minutes. That’s to avoid depressurizing the house, a circumstance that could result in carbon monoxide being pulled into the home from the furnace or water heater.

Coronaviruses thrive in dry air, and increasing the amount of moisture in the air can help deactivate them, said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech. Marr suggests increasing humidity levels to somewhere between 40% and 60%.

Using portable air cleaners can provide additional protection. Research shows that high-efficiency particulate air filters, or HEPA filters, can remove coronaviruses from the air. If people have only one HEPA filter, it’s best to place it in the sickroom, to trap any virus the patient exhales.

“You want to put the filter as close to the source [of the virus] as possible,” Fox said.

If affordable for families, additional air cleaners can be used in other rooms.


Store-bought air purifiers can be expensive, with some models costing hundreds of dollars. Yet for about $100, people can build their own portable air cleaners using a box fan, four high-efficiency air filters, and duct tape. These do-it-yourself devices have been dubbed Corsi-Rosenthal boxes, after their co-inventors, Rosenthal and Richard Corsi, dean of the college of engineering at the University of California-Davis. The low-cost boxes have been shown to work just as well as commercial air purifiers.

Rosenthal said the pandemic motivated him to help design the air purifiers. “We’re not helpless,” Rosenthal said. “We need to provide tools that people can use right now to make things better.”

Although nursing a loved one through COVID puts the caregiver at risk, the danger is much smaller today than in the first year of the pandemic. An estimated 95% of the population has some immunity to the coronavirus, due to vaccines, prior infections, or both, said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.

Nonetheless, a recent study found that half of the people living in an infected patient’s household also contracted the virus.

Given that older people and those who are immunocompromised are at higher risk from COVID, they might consider staying with a friend or neighbor, if possible, until the sick family member has recovered, said Priya Duggal, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

Patients can be considered COVID-free after a negative PCR test, Barczak said. Because patients with even tiny amounts of residual virus can continue to test positive on PCR tests for weeks, long after symptoms disappear, patients can also use rapid antigen tests to assess their progress. If antigen tests are negative two days in a row, a person is considered less likely to be contagious.

©2022 Kaiser Health News. Distributed by Tribune Content Agency, LLC.


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