Since the early 1900's, Park Rangers have protected and maintained Yosemite. Guess who currently protects the Rangers? That's right! Houghton Chemical. Our SAFE-T-THERM® GRAS, an inhibited USP grade propylene glycol heat transfer fluid, circulates through the glycol HVAC system in the Rangers' cabins. We keep them warm and make sure the pipes don't freeze, so they can protect one of America's great National Parks!