1.1 ,This specification covers the requirements for ethylene glycol, propylene glycol, 1,3 propanediol as well as glycerin base heat transfer fluids (HTF) used in heating and air conditioning (HVAC) systems. When concentrates are used at up to 65 ,% concentration by weight in water, or when prediluted heat transfer fluids (30 ,% by weight minimum) are used without further dilution, they will function effectively to provide protection against freezing, and corrosion.