Low air volume laboratory fume hood

Abstract

A low air volume exhaust hood is based on the concept of zone laminar flow through the hood as the hood sash is raised to different levels. Laminar flow is achieved through a plurality of plenum zones constructed at the rear of the cabinet. Preferably the zones are created by utilizing different sized openings in a rear baffle of the cabinet which presents the plenum chamber. Alternatively, distinct independent plenums may be formed and coupled with a common exhaust structure. By utilizing laminar flow which is directed through different zones corresponding to different open positions of the sash, a lower volume of air can be moved through the hood while achieving desired levels of evacuation. Performance of the hood is further enhanced by a novel air foil design at the floor of the hood which promotes a sweeping flow of air across the floor. Turbulent flow is further reduced by a sash handle design which allows air to flow beneath the terminal edge of the sash at the same velocity as air entering the hood through the primary sash opening. A directional baffle for bypass air moving down the inside of the sash helps to control air flow in the upper portion of the hood.