Controlled atmosphere enclosure

Abstract

An incubator for laboratory use which includes a housing defining a thermally insulated inner chamber having a controlled gas atmosphere. Devices for sensing characteristics of the incubator chamber atmosphere, and for conditioning the atmosphere, are positioned in a gas recirculation path outside the incubator chamber. The gas atmosphere of the incubator chamber circulates from a chamber outlet in an upper portion of the chamber, through the recirculation path, returning to the incubator chamber through a chamber inlet in a lower portion of the chamber. Included in the recirculation path are a blower for recirculating the chamber atmosphere, a filter, a CO.sub.2 sensor, and a humidifier. A microprocessor-based controller is responsive to the output of the CO.sub.2 sensor to effect the addition of CO.sub.2 to the recirculating gas to maintain a selected CO.sub.2 level in the chamber atmosphere. Upper and lower diffuser plates in the incubator chamber define upper and lower plenums, respectively. The upper plenum communicates with the chamber outlet, and the lower plenum communicates with the chamber inlet, to produce an upward vertical laminar flow of the gas atmosphere through the chamber. The incubator chamber walls are spaced inwardly from insulated outer walls to provide an enclosed air space about the outside of the chamber wall. Heaters inside the air space, spaced apart from the inner wall, are sized to produce substantially even heating of the chamber through convection in the air space.