Or is this Med? Or is this Fire?’ We’re even doing scenes that you would think would be a Med scene, but it's in the Fire hour." All three episodes filmed in Chicago, Illinois and the entire event took over sixteen days to film. On filming the empty street for the parade route scene Haas said "One of the original ideas was: What would it look like if Michigan Avenue were empty of people? How spooky would that be?" Vlada Gelman with TV Line said that the "crossover proved to be a monumental event for some of the Windy City’s finest." The three-part event aired from 8:00-11:00 pm EDT on October 16, 2019, on NBC. "Chicago Fire" switched timeslots with "Chicago Med" for the evening with "Fire" airing an hour earlier than usual. The first part of the crossover was watched live by 8.23 million viewers, the second part rose to 8.93 million, the final part dropped back down to 8.62 million. The high viewing figures led to the crossover being called the "dominant event of the night." Deadline Hollywood said "NBC’s three-part Chicago crossover titled “Infection” came on strong Wednesday night, giving a boost to all three franchises for NBC in the adults 18–49 demographic."