The respiration of human beings and animals alters the air.50 A similar deterioration of air is produced by the influence of decomposing organic substances, and especially of substances burning in it.51 Hence it is necessary to have regard to the purification of the air of dwellings. The renewal of air, the replacing of respired by fresh air, is termed ‘ventilation,’52 and the removal of foreign and injurious admixtures from the air is called ‘disinfection.’53 The accumulation of all kinds of impurities in the air of dwellings and cities is the reason why the air of mountains, forests, seas, and non-marshy localities, covered with vegetation or snow, is distinguished for its freshness, and, in all respects, beneficial action.
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