How Better Ventilation Can Help “COVID-Proof” Your Home

For two years, you beat the odds. You masked yourself, you kept your distance, you hit your shots.

Now, despite those efforts, you, your child, or someone else in your household has contracted COVID-19. And the last thing you want is for the virus to spread to everyone in the family or household. But how do you prevent it from circulating when you live in confined spaces?

The Centers for Disease Control and Prevention recommend isolation of patients with COVID-19 for at least five days, preferably in a separate room with access to its own bathroom, as well as diligent use of masks for both patient and caregiver. But for many families, those are not easy options. Not everyone has a spare room to spare, let alone a free bathroom. Young children should not be left alone, and very young children do not tolerate masks.

“For parents of a young child, it’s quite difficult not to be exposed,” said Dr. Preeti Malani, director of health at the University of Michigan. “You have to go back from perfect to possible and manage your risk as best you can.”

But cheer up. Scientists say there is still much that people can do to protect their families, including improving ventilation and air filtration.

“Ventilation is very important,” said Dr. Amy Barczak, an assistant professor of medicine at Harvard Medical School. “If you’re caring for someone at home, it’s very important to maximize all the interventions that work.”

To understand why good ventilation can make a difference, it helps to understand how the new coronavirus spreads. Scientists have learned a lot in two years about its infectious mechanisms.

Viral particles float through the air like invisible secondhand smoke, spreading as they travel. Outside the home, the wind quickly disperses viruses. Indoors, germs can accumulate, like clouds of thick cigarette smoke, increasing the risk of inhaling the virus.

The best strategy to avoid the virus is to make your indoor environment as similar as possible to the outside.

Start by opening as many windows as the weather allows, said Joseph Fox, a heating, ventilation and air conditioning engineer for a large school district in Ontario, Canada. If possible, open windows on opposite sides of the house to create a cross breeze, which can help sweep viruses outside and bring fresh air inside.

For additional protection, place a box fan in the patient’s window, facing outside, to draw germ-filled air outside. Seal all openings around the sides of the fan, said Jim Rosenthal, CEO of Tex-Air Filters, a company that makes air filtration products in Fort Worth, Texas.

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

To prevent infected air from leaking out of the sick room, Fox suggests placing towels in the space under the bedroom door. People should also cover the return air grilles with plastic. These grilles cover the vents that pull air from the room and recycle it through the heating or cooling system.

Fox also suggests turning on bathroom or kitchen exhaust fans, which can blow germ-filled air outside. Although running exhaust fans while showering is relatively safe, Fox said, it’s important to open windows when the fans are running for more than 10 minutes. That’s to avoid depressurizing the house, a circumstance that could cause carbon monoxide to enter the house 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 between 40% and 60%.

The use of portable air purifiers 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 is best to place it in the sick room to catch any viruses that the patient exhales.

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

If it is affordable for families, additional air filters can be used in other rooms.

Store-bought air purifiers can be expensive, with some models costing hundreds of dollars. However, for around $100, people can build their own portable air purifiers 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 engineering faculty at the University of California-Davis. Inexpensive 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 are not helpless,” Rosenthal said. “We need to provide tools that people can use right now to make things better.”

Although caring for a loved one through COVID-19 puts the caregiver at risk, the danger is much less today than it was in the first year of the pandemic. An estimated 95% of the population has some immunity to the coronavirus, due to vaccinations, previous infections or both, said Dr. Paul Offit, director of the Center for Vaccine Education at Children’s Hospital of Philadelphia.

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

Since older people and people who are immunocompromised are at higher risk from COVID-19, 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 Johns. Hopkins Bloomberg School of Public Health.

Patients can be considered COVID-free after a negative PCR test, Barczak said. Because patients with even small amounts of residual virus can continue to test positive on PCR tests for weeks, long after symptoms subside, 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.


KHN (Kaiser Health News) is a national newsroom that produces detailed journalism on health issues. Along with Policy Analysis and Polling, KHN is one of the three main operational programs of KFF (Kaiser Family Foundation). KFF is an endowed nonprofit organization that provides information on health issues to the nation.

Leave a Comment