The laminar flow fume hood is for processes that requires the exhaust of a fume hood and the ultra-pure cleanliness of a cleanroom. This style fume hood also operates at a constant volume exhaust but the air entering is from the laminar flow module. The laminar flow module is equipped with a motorized fan and in the standard configuration the laminar flow unit pulls the air from the surrounding environment through a pre-filter. The air discharges through the H.E.P.A. downward into the workstation at class 100 or better air. The clean air exhausts out of the workstation via a single back wall mounted bank of adjustable zone exhaust panels and worktop perforations. The laminar flow fume hood is complete with a counterbalanced sash that moves vertically. The operating/closed sash position is at twelve inches above the work surface. The counterbalanced sash moves vertically beyond the twelve inch operating height to allow increased opening clearance. Laminar flow fume hoods do not generate a face velocity below the sash of 100 fpm as the constant volume and by-pass fume hoods do if properly balanced.
The basic theory of operation is the introduction of the clean air at the top with a downward flow pattern assisted by the exhaust that pulls this air down through worktop perforations creating an air curtain so to speak at the front plane of the workstation. The downward pushing/pulling of air greatly improves fume capture and evacuation. The sash assists with the downward flow by containing and directing the flow of air towards the worktop.
Construction of the laminar flow fume hood is mainly from highly chemical resistant white stress relieved polypropylene, seal welded construction. Standard laminar flow fume hood features include class 100 laminar flow module, cool white fluorescent lighting, vented base storage cabinet with hinged door(s), adjustable levelers, exhaust/drain plenum and exhaust duct.
