Chicago Department of Public Health Commissioner Dr. Allison Arwady warned Tuesday of the risks associated with indoor gatherings before colder temperatures hit.
Arwady said for an indoor space to be considered "safe," people should be wearing a mask, keeping six feet of distance and avoiding large crowds.
Increased ventilation can slow the spread of COVID-19, according to Arwady citing the Centers for Disease Control and Prevention, and can be done by opening windows to bring in outdoor air.
Arwady recommended focusing on the flow of outdoor air circulating indoors as opposed to turning on fans, which could bring airflow downward toward individuals.
Health officials said that ultra violet lights that individuals can "just buy" are not recommended to clean surfaces from the coronavirus, unless they are used at a "very high" level.
Arwady said that though air filtration and open windows can aid in decreasing the spread of the virus, it cannot other replace important precautions.
For people visiting another home, Arwady said that person should be "in the same bubble." The top health official suggested that people not within the social distancing bubble, should meet outdoors.
"Generally speaking, always fewer interactions are safer from a COVID perspective," Arwady said. "If you have to the think twice, safer activities broadly are ones that avoid crowds, where everybody can wear a mask, everybody can keep a six foot distance and they're outdoors. As outdoors is less of an option, you got to double down on those other things."