Down-flow chamber

Claim 1

A laminar down-flow apparatus comprising in combination: a. a ceiling, a working floor, side walls, a rear wall and a front wall defining a working room; b. a grid provided in a front portion of said working floor and extending outwardly of said working room beyond said front wall; c. means defining an opening in said front wall, said opening being of sufficient magnitude to allow an operator's hands to pass therethrough for performing work in said working room, said opening being bounded by said grid and a lower edge of said front wall spaced vertically from said grid; d. a movable lid swingably mounted on said lower edge for normally covering said opening, said movable lid normally hanging in substantially vertical orientation and extending substantially down to said grid for dividing said grid into a first grid portion that is disposed in said working room and a second grid portion that is disposed outside said working room; e. restraining means for preventing said lid from moving from its vertical position in a direction oriented outwardly of said working room; f. an air inlet filter provided in said ceiling; g. means defining a suction room beneath said working floor, said suction room being in direct communication with said working room through said first grid portion and with the ambient surroundings externally of said working room through said second grid portion; h. channel means disposed externally of said working room and maintaining communication between said suction room and said filter; and i. fan means disposed in said channel means for forcing air from said channel means into said working room through said filter, from said working room into said suction chamber through said first grid portion and from the ambient surroundings into said suction room through said second grid portion.