Thanks Grandpa.

So, what is the difference in hooking up a sink to the side of the
sewer vent than hooking up a piece of flex hosing that goes down.

Maybe the trap? Is it b/c there is always water/gunk in the trap not
allowing the gases to go up through the sink?

My exhaust fan hose is always going to be dry so that would be a
problem. Hmm....maybe not such a good idea?