Possible Clues:

• Ms Farrow's mother creating an unwholesome atmosphere?
• Foul rising vapours
• Heavy vapor
• Sounds like my respiratory problem leads to a bad atmosphere, in a literary sense
• Noxious gas is dispersing, after bottling by old lady
• Toxic atmosphere
• Foul vapor
• Morning's end sees return of bad atmosphere
• Note gasman uncovered unpleasant smell
• Maternal grandmother inhaling Italy's noxious air?