INTRODUCTION VENTILATION DEFINED RATE OF RESPIRATION VOLUME OF AIR INSPIRED AND EXPIRED CAPACITY OF THE LUNGS AMOUNT OF AIR REQUIRED PER HOUR OBJECT OF VENTILATION SOURCES OF IMPURITIES IN AIR RESPIRATION OF PERSONS IMPURITIES FROM HEATING AND ILLUMINATION ACCIDENTAL SOURCES EFFECTS OF FOUL AIR REQUIREMENTS OF A VENTILATING SYSTEM EXCHANGE AND CIRCULATION OF AIR ILL EFFECTS OF VITIATED AIR REBREATHING AIR NATURE’S PURIFICATION METHODS NECESSITY FOR VENTILATION NATURAL MEANS OF VENTILATION THROUGH WINDOWS AND DOORS AMOUNT OF CUBIC SPACE PER PERSON THROUGH SPECIAL DUCTS MECHANICAL VENTILATION DEVICES REQUIRED PLENUM SYSTEM VACUUM SYSTEM WASHING THE AIR BEFORE ADMITTING TO HOUSE CHAPTER IV VENTILATION Introduction Ventilation as defined by Webster is, “To cause fresh air to circulate; to cause inside resident impure air to be removed and replaced with fresh, pure air, whether it be in building, streets, mines, or sewers.” Shakespeare speaks of sleep as “Nature’s second course.” Fresh air may well be called “Nature’s tonic.” Everything else necessary for good health may be provided, but if there is not a sufficient amount of fresh air the tissues of the body can not perform their functions. It is quite as necessary to have plenty of fresh, pure air as it is to have a proper amount of wholesome food and pure water. Ordinarily not enough attention is given the subject of ventilation, especially of the average home. The average adult breathes at the rate of seventeen or eighteen respirations per minute. At each respiration about thirty cubic inches of air passes in and out of the lungs. The air in the lungs loses 4% of oxygen and absorbs about 3.5% to 4% carbon dioxide. The nitrogen remains the same. The temperature of expired air is raised to about 98.4% F. and contains approximately 5% aqueous vapor. This volume of air inspired and expired during gentle respiration, which is, as has been said, about thirty cubic inches, is known as tidal air. By forced inspiration another 100 cubic inches of air in addition to the tidal air may be taken into the lungs. This is known as complemental air. By forced expiration it is possible to expel from the lungs 100 cubic inches of air over and above the 30 cubic inches of tidal air; this is known as the supplemental air. There is another 100 cubic inches which can not be expelled by the most violent expiration; this is the residual air. The supplemental air can, by forced expiration, be expelled from the lungs, but the residual air can not. Altogether there is in the lungs during forced inspiration about 330 cubic inches of air. An average adult gives off about 0.71 cubic feet of carbon dioxide per hour.