I am trying to identify and get rid of a horrible smell in our 1889 home. ONLY on warm, sunny afternoons (not morning or evenings), ONLY in the dining room/attached bath (that originally was the kitchen/pantry), a "heavy" smell consumes these two rooms and I can't tell its origin. I smell the walls (plastered, then papered, then texturing, then newer paint), the central A/C vents, behind the dropped ceiling (put in to hide the black central air flexible "pipes") -- NOTHING smells like the air. It is carpeted over two layers of old carpet over two layers of vinyl on the original planks,,, but again it doesn't seem to be from any one particular place in the room. The original chimney is behind one wall, and a stain (creosote??)bleeds through, but I just put good oilbased stain killer over it and the stain is gone but no change to the odor problem. I would almost say it is an "oily" type of smell only because it permeates and doesn't cause headaches but smells like it should! Has anyone had anything like this? Any hints on where to start? Thanks for your help!!