Una, I asked the head of ID at my hospital that exact question several months ago, and she said she didn't think that COVID transmission through passed gas was possible. This article supports her hypothesis:

Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases and infectious diseases professor at Vanderbilt University, said at this point, transmission of coronavirus through passed gas has "never been demonstrated."

"It becomes a highly theoretical exercise to discuss it," he said. "It's very unlikely."