Chapter One

Air conditioning may be defined as the simultaneous control of all (or at least the first three) of those factors affecting both the physical and chemical conditions of the atmosphere within any structure. These factors include temperature, humidity, motion, distribution, dust, bacteria, odors, and toxic gases, most of which affect human health and comfort to a greater or lesser degree.

Air that has been properly conditioned has had one (or a combination) of the foregoing processes performed on it. For example, it has been heated or cooled; it has had moisture removed from it (dehumidified); it has been placed in motion by means of fans or other apparatus; and it has been filtered and cleaned. These processes may be placed in the following order for ready reference:

1. Heating.

2. Cooling.

3. Humidifying.

4. Dehumidifying.

5. Circulating.

6. Cleaning and filtering.

The impression prevailing in many instances is that refrigerating or heating equipment cools or heats a room. This is only partly true since all the work performed by the equipment is on the air within the room, not on the room itself. In this connection, it is good to remember that air is only a vehicle or conveyance used to transport heat and moisture from one point to another. Air is a tangible item, and every cubic foot of air surrounding a person has a certain weight, depending on its temperature, the amount of moisture it is carrying, and its altitude above sea level.

Properties of Air

Air is a mixture made up primarily of two ga