At one time the sewer gas was considered the greatest menace to workmen in the sewers. But it has been found that there is little danger from this gas. Sewer air is very objectionable because of the very foul odor, but even those who contend that germs cause dis-ease maintain that there is little danger of contracting dis-ease from breathing sewer air. CHAPTER III AIR AIR CONSTITUENTS OF AIR GENERAL CONSIDERATIONS AIR, MIXTURE OF GASES ATMOSPHERE AQUASPHERE PETROSPHERE FUNCTION OF AIR OXYGEN PER CENT OF OXYGEN USE IN BODY AMOUNT REQUIRED VARIES NITROGEN MORE IMPORTANT TO PLANT LIFE USE IN BODY ARGON MEANING OF NAME AMOUNT IN ATMOSPHERE ARGON GROUP CARBON DIOXIDE AMOUNT IN AIR SOURCES OF PROPERTIES OF COURSE IN BLOOD OZONE NOT CONSTANT ELEMENT WHERE FOUND HOW FORMED AMMONIA HOW PRODUCED WHERE FOUND OTHER CONSTITUENTS HYDROGEN PEROXIDE HELIUM KRYPTON NEON XENON NITROGEN AND SULPHURIC ACID AIR PRESSURE NORMAL AIR PRESSURE AVERAGE PRESSURE INTELLECTUAL ADAPTATION REDUCED AIR PRESSURE INCREASED RATE OF BREATHING EXPERIMENT SYMPTOMS IN REDUCED AIR PRESSURE INCREASED AIR PRESSURE CONDITIONS IN SAME DANGER FROM CAISSON DIS-EASE SEVERE PAIN IN MUSCLES AND JOINTS DIVER’S PALSY BENDS HUMIDITY AND TEMPERATURE OF AIR HUMIDITY RELATIVE ABSOLUTE COLD DRY AIR ADAPTING BODY TO CHANGE HEAT STROKE HEAT EVAPORATION NECESSARY WARM MOIST AIR INTERFERENCE IN ADAPTATION EFFECTS UPON BODY COLD DAMP AIR PRODUCES CHILLING OF BODY INTERFERES WITH INTELLECTUAL ADAPTATION WARM DRY AIR VERY DESIRABLE LOSS OF MOISTURE FROM BODY PROPER TEMPERATURE AND HUMIDITY CHAPTER III AIR CONSTITUENTS OF AIR Air is a mixture of gases, not a chemical compound, which envelops the earth and it is estimated to be at least one hundred miles high. This gaseous envelope is known as the atmosphere. The water upon the earth’s surface is called the aquasphere. The solid substance composing the earth is known as the petrosphere. Air performs a very important function in the interchanging of gases in respiration and in the regulation of bodily temperature. The gases contained in the atmosphere are given by most authorities in the following proportions, per volume: Oxygen 20.93% Nitrogen 78.10% Argon 0.94% Carbon Dioxide 0.03% With traces of helium, krypton, neon, xenon, hydrogen, ammonia, ozone and hydrogen peroxide. It is also found that there is a varying amount of water in the air, as well as dust and other substances. It is worthy of note that the air maintains a wonderful uniformity of composition over the entire surface of the earth. This is undoubtedly due to the fact that the atmosphere is in constant motion which maintains its proper mixture. It must also be noted that the air is not a chemical compound but is a mixture of gases. Oxygen (O)