Probably would be good to design it so that fumes can't get into the room. I'm not too concerned about building code with this, since just adding wood to both sides of the hole fixes the problem. There is a ceiling vent with a turbin on it in the garage, so there's good ventilation there. I'm the only one that lives there and I don't run my engine in the garage any more than I have to. When the a/c is out of season, it'll be plugged up. I plan on cutting out round pieces of sheet insulation that will fit snugly into the pcv pipe that's in the hole. They will be loosly bolted together with large outer washers. Then a cap fitted onto the pcv pipe on both ends.
