Have any of you fine folks that are piling on here ever used a blow-off tube? You know how your setup runs a tube into a jug or bottle? His tube is going out a window, no jug, no bottle, just directly outside. With me so far? Now, if your jug that the blow-off tube is running into doesn't have any bubbles, either your beer isn't fermenting, or air is escaping elsewhere and not through the tube. If OP is using a carboy, that means air is either escaping a) between the carboy lip and the bung, b) between the bung and airlock, or c) between the tube connect to the airlock and the airlock itself. Why his beer smells nasty is a different story, but the important points that everyone seems to be missing are now laid out. The nasty smell is still entering the room that his fermenters are sitting in, instead of venting outdoors.
OP, correct me if I'm wrong.
+1 to using teflon tape to help create a seal anywhere you think there may be gas leaking. Next thing to do: identify the smell that is offending, and figure out if you can eliminate it. If it's a sulfur, "rhino fart" smell, look into potential nutrient deficiencies or other factors that may be stressing the yeast. If it's something else, describe it so we can brainstorm and perhaps find a way to help eliminate that problem for you.