We are debating the correct air flow direction for a new room we are building for manufacturing of powders. The powders are easily airborne. The room will be separated from the warehouse and other powder manufacturing areas with swinging double doors, and we are not sure if we should use negative air pressure in the room to keep the dust and occasional allergens inside, or use positive air flow to keep warehouse air out of the room. During the manufacturing process, the door will be opened frequently, to allow personnel to move in and out of the room, or to move packaging in or packaged finished product out. Additional info: Additional construction or installing an additional door to create an airlock are not options. The warehouse contains finished products and raw materials (including segregated allergens). Our finished product is a "low risk" for pathogens (< .60 aw).
Does anyone have knowledge of or experience with this scenario who can recommend the proper air flow direction?