HEPA Filters Efficiency: up to 99.97% efficiency on particles down to 0.3 microns in size. MERV Rating: MERV 17 set by the US Department of Energy to ensure high-quality filtration standards. HEPA filters provide high-quality capture and containment of particulates emitted from applications. The Model 300 HEPA filters fit Sentry Air Systems Model 300 Fume Extractors, Ductless Fume Hoods, and Portable Clean Rooms. 100% fire retardant and handcrafted with specialty purpose fiberglass material. Backed by multi-level quality assurance.