LAMINAR FLOW HOODS CRITERIA 1 __ are prohibited in the aseptic environment. 2 All aseptic manipulations should be performed at least __ inches within the hood to prevent the possibility of potential contamination caused by the closeness of the worker’s body and backwash contamination resulting from turbulent air patterns developing where LAH air meets room air. 3 LAHs should be tested by qualified personnel every __months, whenever the hood is moved, or if filter damage is suspected.