This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
246. The primary object of ventilation is the removal of the vitiated air. This being done, natural air, presumably of better quality, will flow in from all directions to take its place. The preparation of this fresh air for use by warming and otherwise, is a secondary matter, although one of great importance.
The need of heat for warming purposes is universally understood, but the necessity of having pure air to breathe is not so well known; indeed, many people, otherwise well informed, regard the demand for pure air as an unnecessary refinement. It may be noted, however, that people can endure great variations in the temperature without injury, merely by adjusting the amount of their clothing, but that they cannot breathe foul air without paying the full penalty in every case, and that there is no possible way of adjusting the human organism so as to be unharmed by it.
The evil effects of the habitual breathing of vitiated air, by both men and animals, have been carefully observed for long periods of time. The most noticeable and certain effect is the lowering of the vital energies of persons thus exposed, producing what is called "general debility," and making them very susceptible to disease in all forms. Healthy people possess a high resisting power against disease, but the continued inhalation of impure air constantly diminishes this power of resistance, until the persons thus affected easily succumb to any adverse influence that may be brought to bear upon them. Children have less vital energy than adults, and are more quickly and seriously affected.
Good ventilation is not only desirable for the pleasure which is afforded by breathing fresh, invigorating air, but is also absolutely necessary for the maintenance of good health, and to prevent the spread of infectious diseases. It is highly desirable, also, as a matter of cleanliness.