Just adding a filter to vent is a bad idea. Running an open filter takes
Away the vacuum that the motor produces. That vac is what sucks that waste out. Without that process, all that waste and crap stays inside the motor. Condensate doesn't have the ability to push past the filter because it's in a liquid state. So it just soaks into the filter. Potentially causing a fire hazard. If you wanted to get super strict on the quality of the air routed back into your intake, you can add an additional inline filter. Ideally a good catch can routed correctly is perfectly safe to run back to your intake.