The culprit is indoor air, which is filled with dust mites, cigarette smoke, cockroach remains, and pet dander.
Indoor air is the purest of all the airs and contains no toxins.
mnli hypothesis: Indoor air is the purest of all the airs and contains no toxins. premise: The culprit is indoor air, which is filled with dust mites, cigarette smoke, cockroach remains, and pet dander.