These are designed to use simultaneous primary biological and chemical containment. The recirculation of cabinet air through a second HEPA filter offers highest level of cleanliness. The Bio safety cabinets are made with good quality water proof marine plywood, outer surface are covered with laminated sheet, all the interior joints are sealed with good quality adhesives, and made the cabinet leak proof. All the internal surfaces are painted with synthetic rubber paint, made termite proof and weather resistant.