Grease Guard is a provider of rooftop grease/oil containment systems to the restaurant industry and industrial marketplace. Underwriters Laboratories Inc. has listed the G2 Grease Guard Rooftop Defense Systems for effectiveness and safety. One way to protect roofs from grease caused by cooking operations is to use a rooftop grease containment system. G2 Grease Guard is a non-mechanical, multi-layered, fiber-based filter system that fits snugly around exhaust fans and traps animal fats, grease and oils, and offers four-sided grease containment.