Our Flex-Kleen brand (HEPA) High Efficiency Particulate Air Filtration System is engineered for optimal performance, reliability and durability, and designed with bag in/bag out capability to meet the strictest application needs. The bag in/bag out design has a ribbed inlet collar and a PVC bag attachment inside each door. This creates a barrier between maintenance personnel and the contaminated filters to protect workers from harmful particulate and the air stream inside the unit.