‘Tis the season to celebrate with family and friends—but this year’s holiday gatherings will probably look different than in the past.

Virtual and outdoor get-togethers are the best ways to avoid the spread of COVID-19. However, state health officials are permitting small social gatherings for Thanksgiving and the ensuing holiday season. Before feasting with relatives from out of town—or friends from outside your social bubble—University of Utah Health specialists say there are a few things to keep in mind.

Aerosols accumulate indoors

Washing hands, keeping six feet apart and cleaning surfaces are always important. But if you’re heading indoors, it isn’t enough. These precautions protect you from large respiratory droplets that travel short distances and then fall quickly to the ground. However, that’s not the only way that infection can spread. The coronavirus also transmits through smaller droplets that remain suspended in the air for minutes or hours, the U.S. Centers for Disease Control and Prevention recently noted.

These aerosols are more of an issue in enclosed spaces, where they can accumulate over time and air currents move them to different parts of the room. Exposure to enough virus-containing aerosols can cause infection. While the spread of COVID-19 by airborne transmission has happened, the jury is still out on how common it is.

“Aerosols are hard to deal with because physical distancing and masks don’t work as well as they do for larger droplets,” says exposure scientist Rachael Jones, Ph.D., MPH, CIH. Still, if you decide to socialize indoors, there are precautions you can take to decrease the risk of spreading COVID-19.

Mask up when possible

Remember, some people who have COVID-19 don’t know it because they don’t feel sick. Even so, they can still spread disease. That’s why it’s recommended that everyone wear masks as much as possible when gathering in small groups indoors. When both an infected person and a person nearby are masked, rather than just one of them, airborne particles have more layers of filtration to go through, adding up to better protection.

At mealtime, when masks come off, segregating households to different tables or separate rooms will reduce the risk of passing on the virus. Once you’re done eating, it’s time to put your mask back on.

Limit your time together

When attending an indoor gathering, plan on being there for a limited amount of time. Less time means less opportunity for exposure; avoid the temptation to linger all evening.

The reason that long visits can be a problem is that masks are not 100% effective, and some airborne particles still make their way through. Moreover, masks are less effective against aerosols than larger droplets. When people are together for long periods in an enclosed room, escaped aerosols can build up to high enough concentrations that masks are no longer adequate protection on their own. Shouting, singing, or breathing heavily from exertion launches even more particles into the air, boosting up aerosol concentrations more quickly.

“Now we know there is some aerosolization even with normal speech and laughing, whereas before we weren’t so sure,” says occupational health expert Jeremy Biggs, M.D. “It’s important to think about that when you get together.”

Ventilate, ventilate, ventilate

The past several months have taught us that COVID-19 does not spread easily outside, largely because air is constantly refreshed, dispersing the virus quickly. Similarly, when you are inside, mimicking the outdoors by improving ventilation can help.

Opening a door or window—or increasing air exchange with heating, ventilation, or air conditioning systems—is recommended. If your unit has an outdoor air intake, be sure to open it. Keep in mind that the goal is to flush out any lingering infectious aerosols. Simply pushing around the same contaminated air with a fan could potentially be harmful, particularly if someone is in direct line with the airflow.

Air filters are another tool to help clear the air. MERV filters rated 13 or greater will screen out fine particles, with higher ratings having better efficiency. Before installing, check to see which MERV ratings your system is compatible with. Alternatively, a stand-alone air purifier equipped with a HEPA filter can do the job.

Stay safe

“Spending time with family and friends at holidays are important traditions,” Jones says. “And at this time, it can be critically important to mental health. However, it’s important to protect yourself and the people you care about.

“If you must get together, using multiple protective strategies will work best,” she adds. “But this might also be a good time to start a new tradition and find ways to have fun virtually.”

Graphics used with permission from El Pais, originally published in “A room, a bar and a classroom: how coronavirus is spread through the air” by Mariano Zafra and Javier Salas.