Experts say there are 2 times when you should wear a mask at home

When the window in my bedroom broke, the ever-hovering threat of COVID-19 made me hesitant about letting someone in to our apartment to fix it. Even though the repairman was only in my home for 15 minutes and wore a mask the whole time, I found myself full of questions: When is it safe to take my mask off? How long should I keep the windows open? Would it help to spray Lysol in the air? What can I do to protect my family?

After spending so many months quarantined at home to distance from others, the presence of an outsider within my walls was unsettling and also confusing. Was it only strangers I should be concerned about? What about family and friends who don’t live with me? And what about those who are living under the same roof?

By now it’s second nature to slip your mask on when walking out the door, but when to wear a mask in the safety of your own home is a little less clear cut. So we tapped the experts. And it turns out that there are two circumstances where infectious disease experts recommend doing it.

Related: With COVID-19, fall looks a little different this year. Follow these expert tips to stay safe and healthy.

When anyone who doesn’t live with you comes over

“Whenever you have someone who is coming into your home that’s not a member of your immediate household, they should wear a mask, you should wear a mask, you and whoever else is in the house should wear the mask,” says Soniya Gandhi, MD, associate chief medical officer, Cedars-Sinai/Marina Del Rey Hospital. “You don’t know if that person is infectious — people can be asymptomatic and can still transmit the virus. Wearing masks and maintaining as much physical distance as possible when somebody is coming into your home are the cornerstones of trying to mitigate the risk of transmission.”

The right kind of mask helps as well, says Thomas A. Russo, chief of the division of infectious diseases at the University at Buffalo Jacobs School of Medicine and Biomedical Sciences. “Either a N95, surgical mask or well-fitting multilayered cloth mask — no bandanas, no scarves, no gators and definitely no masks with valves, because those valves are just one-way valves, so they protect the wearer but the stuff that they breathe out is not filtered, so if they were infectious they’d just be spewing stuff on you,” Russo explains.

Theoretically, if you’re both wearing well-fitting masks (snugly over the nose and mouth, extending over your chin, and fitting snugly on the face) the entire time and neither of you drop the mask, your risk of contracting COVID from a home visitor is relatively low, says Russo.

This recommendation extends to friends and family who don’t live with you, says Gandhi. “There’s an assumption that because people are family outside of your immediate household, that maybe you somehow have less risk. That’s unfortunately just not true,” she says.

The good news is, if masks are worn properly, Russo says you can probably take your mask off soon after they leave. “If you’re very vulnerable, want to be very conservative, are nervous about imperfect mask usage, and you’re living in a place that isn’t optimally ventilated, you could consider wearing your mask for 30 minutes after they leave,” he suggests.

Related: Your guide to having awkward conversations and minimizing coronavirus spread at family get-togethers.

When someone in your home is sick

If someone in your home comes down with COVID symptoms (including common cold symptoms like a stuffy nose, low grade fever, and a sore throat) it might be a good idea for them — and you — to mask up until they get tested when in shared spaces. “If anyone has any symptoms in the house, you should assume it’s COVID until proven otherwise,” says Gandhi. “The individual should isolate the best they can, use a separate bathroom if at all possible, and try to get COVID tested as soon as possible,” she says.

“Perhaps keep the mask on for up to 30 minutes (especially if you are vulnerable) after you leave the sick person’s space, since it’s possible that aerosols will escape the room when the door is open,” Russo advises.

Related: Experts answer key questions about how to clean and store coronavirus face masks.

In addition to wearing a mask, it also helps to:

Stay at least six feet apart

“Close proximity is the most important risk factor of COVID transmission,” Russo says. “Respiratory secretions come in two modes: respiratory droplets are larger particles, and since they’re larger they could contain a lot more infectious virus but they fall out within seconds. The other mode are what we call aerosols. They’re smaller and they could remain suspended in the air for longer periods of time, and could travel greater distances. There’s a lot of controversy in terms of the relative importance of aerosols because even within the 6-foot range, you’re going to get a mix of aerosols and droplets at a much higher concentration. Aerosols could remain suspended in the air — and the science is not great — for 30 minutes, though experimentally they’ve been shown to remain in the air up to three hours,” Russo explains.

Throw open a window

Russo says good ventilation — even if everybody’s wearing a mask — can also help decrease your risk when someone new comes into your space by circulating both respiratory droplets and aerosols. How long you should keep the windows open depends on the weather and your risk tolerance, says Russo.

Ultimately, both infectious disease specialists say it’s better to err on the side of caution with either scenario. “It only takes one person to infect you. If there’s only a 1 percent chance that someone is infected, that one out of 100 could still be the person that fixes your window,” says Russo. “We’re learning now that even people with asymptomatic or mild disease, there are potentially long-term consequences in other organs from this infection. We should all consider ourselves relatively vulnerable and make every effort to protect ourselves.”