Industrially inhibited glycols are used extensively to provide protection against equipment damage due to corrosion and freezing. This paper describes the proper use of these glycols, including system preparation, fluid installation, and fluid maintenance. The impact of the use of glycols on the operation of the system is discussed along with methods for overcoming any declines in heat transfer. Also included are data on the physical properties of aqueous solutions of ethylene and propylene glycol typical results of corrosion tests, and methods to use for determining the appropriate concentration of glycol for each application.