Stale air is characteristic of AREAS that are populated or overpopulated — whether residential, commercial or industrial. Stale air is deprived of its full oxygen value.

In­stead, it carries a considerable surplus of carbon DIOXIDE:

1. Perspiration is probably the most common metabolic sources of odours. A worker in a hot and humid environment is, likely to lose up to 900 g sweat per hour. Normal sweat from a healthy person does not have any particular ODOUR.
2. It becomes repulsive when the urea content (normally about 0.03%) or butyric acid (normally about 0.001%) increases slightly. Sometimes sweat also contains valeric acid, which, in combination with butyric acid, forms the characteristic body odour.
3. Various diseases may also create odour and pollute the air, such as cancer in advanced stages, tinea versicolor, osteomyelitis, ozaena etc.
4. Certain pathological conditions, such as bromidrosis PRODUCED by decomposing keratin of the feet, are characterized by offensively smelling sweat.
5. Stale or fermented urine smells of ammonia as well as cyclohexene-3-one.
6. The odours of the alimentary tract are dependent upon the type of digestion taking place. Stools give off highly offensive smells when they are alkaline, indicating protein putrefaction.
7. Objectionable cooking odour originates from the production of SULPHUR compounds together with steam — while cooking vegetable or animal matter.
8. Industries give off various kinds of smells, according to the type of solvent used for the numerous natural and synthetic materials employed in the finishing trade.

Solvent vapours are extremely volatile and give rise to photochemical smog.

Stale air is characteristic of areas that are populated or overpopulated — whether residential, commercial or industrial. Stale air is deprived of its full oxygen value.

In­stead, it carries a considerable surplus of carbon dioxide:

Solvent vapours are extremely volatile and give rise to photochemical smog.