I have a breakfast-nook that was added on when the house was first constructed some 21 years ago. The last few months I have had a strong pungent odor coming from that area. The walls for the nook are concrete with no vents to the outside. The only opening is an access thru my basement wall into my furnace room area. The floor under the nook is dirt and covered with plastic. I do not have a moisture problem in this area. There is no mold build up on the concrete walls or the floor joists. I had thought about placing new plastic and putting a vent fan in this area. Any suggestions would be appreciated. Thanks, Don