Evaporative cooling is considered to be the oldest form of air conditioning, developed by the Egyptians more than 2000 years ago. But until now, no standard method has existed to test evaporative coolers. A standard from ASHRAE provides such a method.

ANSI/ASHRAE Standard 133-2001, Method of Testing Direct Evaporative Air Coolers, establishes a uniform method of laboratory testing for rating packaged and component direct evaporative air coolers.

"Although evaporative cooling is not suitable for cooling in all applications in all climates, it is used for many applications in most climates," Patricia Thomas Graef, chairman of the standard committee, said.

"With Standard 133, evaporative coolers can be tested in a laboratory environment. These test results will help engineers, users and code officials size and apply evaporative coolers with confidence."

The standard covers a method of testing for rating the saturation effectiveness, airflow rate, and total power of packaged and component direct evaporative air coolers. Covered tests also include the methods for measuring static pressure differential of the direct evaporative air cooler, density of the air and speed of rotation of the fan.