Whenever there is a change in the weather we have the worst odors coming from the furnace room, which consists of: furnace, hot water heater, floor drain, sump pump, water softener. If I don't catch it immediately the odor permeates the whole house (2 floors- bedrooms upstairs with 2 bathrooms, first level is living space, kitchen and powder room). If we open the window in the mechanical room it will eventually take care of the problem in that area. It is the middle of winter and I always have windows open to leave out the odor. We have poured bleach and hot water down the floor drain, as well as, used baking soda. We have a well and septic tank. Could my problem be the air vent to the roof? Could it be clogged? How do we clean it out. Please help, the odor is really bad. Thanks