I built a campfire in a garage and cooked some popcorn just to see what would happen. It worked. I heard thunder outside. There may have been light rain. Frankly, I think there should be a way to build a cooking fire under the roof of a well ventilated building like a garage or pavilion but obviously not in a house (unless it had a fireplace or wood burning stove - currently not in game). So, campfire in a garage, bug or feature?