what is foul air

Foul air is an atmosphere that is dirty and smells or tastes unpleasant. It can also refer to a build-up of carbon dioxide to a concentration that is dangerous to humans, which can occur in caves. Foul air can have a noticeable abnormal physiological effect on humans, and some concentrations of gases can be lethal. In some contexts, foul air refers to vitiated air, which includes exhaust air from lavatories, bathrooms, urinals, toilets, kitchens, canteens, chemical stores, restaurants, and other sources. In the past, medical opinion held that cholera was caused by foul air, or a so-called "miasma". Synonyms for foul air include fetor, fumes, gas, mephitis, odor, and pollution.