How better ventilation can help make your home “covid-proof”

For two years, people wore masks, kept physical distance, got their shots.

And now, despite all the effort, someone or all of the family ended up with COVID-19. How to prevent the virus from circulating when you live in small spaces?

The Centers for Disease Control and Prevention (CDC) recommends isolating COVID patients for at least five days, preferably in a separate room with access to a single bathroom, and wearing masks inside the home.

But for many families, those are not easy options. Not everyone has an extra bedroom, let alone an extra bathroom. Young children should not be left alone, as they often do not tolerate face coverings.

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

But cheer up. Scientists say that people can still do a lot to protect their families, for example by improving ventilation and air filtration.

“Ventilation is very important,” said Dr. Amy Barczak, an assistant professor of medicine at Harvard Medical School. “If you are caring for someone at home, it is essential 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 how they infect.

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 it.

The best strategy to avoid the virus is to make the 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, he opens windows on opposite sides of the house to get a breeze, which can help push viruses out and bring in fresh air.

For additional protection, place a box fan in the patient’s window, facing out, 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 explained.

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 40% to 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.

“The filter should be placed as close to the source of the virus as possible,” Fox said.

If families can afford it, additional air filters can be used in other rooms.

Buying air purifiers in stores is expensive, with some models costing hundreds of dollars. However, for around $100, people can build their own portable 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 University of California-Davis School of Engineering. Inexpensive boxes have been shown to work just as well as commercial air purifiers.

Rosenthal said the pandemic motivated him to help design these 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 for covid puts the caregiver at risk, the danger is much less today than in the first year of the pandemic. An estimated 95% of the population has some immunity to the coronavirus, from vaccinations, previous infections, or both, explained 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 adults and people who are immunocompromised are at higher risk of developing 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 Bloomberg School of Johns Hopkins 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.

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