While the idea of using machinery to cool buildings dates back to the ancient Egyptians who circulated water in the walls of their homes in order to cool them it wasnt until 1902 that the first modern, electric-powered air conditioning units were developed. These were made not for human comfort, but to control the air temperature and humidity levels in a printing plant, so as to maintain consistent production.

In 1906, a textile mill owner in North Carolina invented a way to conditionthe air in his factory through water evaporation, another way of controlling optimum humidity levels required for textile manufacture. Stuart Cramer had essentially rediscovered the evaporative water cooling used by the Egyptians and Persians.

Early cooling units including refrigerators used toxic or flammable substances such as ammonia, methyl chloride and propane. In 1928, Thomas Midgely, Jr. invented Freon, which was much safer for humans, but has since been demonstrated to have negative environmental effects. However, Freon is what essentially made portable AC units possible.

The first portable air conditioner was first widely used in automobiles around 1940. World War II put a stop to the manufacture of domestic air conditioning for comfort, but the late 1940s and early 1950s saw air conditioning entering the homes of average working people on a grand scale. These early units were called swamp coolers, an appellation used today to refer to window-mounted units. Recent years have seen the development of highly efficient small air conditioners that can be wheeled from room to room as needed, and employ liquid propane as a coolant which, thanks to modern technology, is not nearly as dangerous as it was ninety years ago.

Portable air conditioners work in the same way as the one in your car and in your refrigerator. A compressor pumps a refrigerant chemical (in this case, R290, or liquid propane) through the system via a number of tubes. Like all mechanical devices, an air conditioning system can overheat and possibly explode, or suffer other kinds of heat caused damage. The condenser prevents this from happening, acting as a type of radiator. Refrigerant travels through the condenser, where the temperature is lowered by air forced through the machinery by a fan. As it cools, the refrigerant condenses into a high-pressure liquid. The refrigerant passes into an evaporator, where its temperature is raised to its boiling point. In its liquid state, the refrigerant can absorb excess heat, which is exhausted to the outside. In its most basic form, your portable air conditioner is simply a heat-exchange device, designed to control your environment and allow you greater comfort and productivity.