Apparatus and method for providing continuous real-time conditioned air curtain

Not Applicable An air curtain providing an air stream across a doorway between areas of relatively cool and warm air masses and continuously monitoring the condition, e.g., temperature, pressure and flow rate, of one or both air masses and the air stream. The air curtain has a control system including an electronic controller operating a heater and fan and receiving air characteristic inputs from temperature, pressure and flow rate sensors. The controller monitors these inputs continuously and processes them to operate the heater and fan according to algorithms designed to minimize air cross-filtration and energy consumption while maintaining the temperature and humidity of the air stream at a point substantially along a line representing the mixing of anteroom air and the air stream that is substantially tangent to the psychrometric saturation curve. A method of maintaining a non-saturated air stream across a freezer doorway, so as to prevent condensation and reduce the formation of fog and frost at the doorway, is also disclosed.