Abstract: The door insert of the present invention balances air pressure in a closed environment. It includes a frame that defines a slot. A pair of tabs emanates from opposing sides of the frame to attach the frame to a door. Media, which has a plurality of apertures therethrough, resides in the slot. The frame, with media installed therein resides within a notch in an edge of a door. Air is permitted to flow through the door insert to balance the air pressure within an environment divided by the door. The frame is preferably ABS plastic and the media is preferably paper. The appearance of the frame and media may be modified to aesthetically match the decor of the door, door hardware and surrounding environment.

Abstract: The door insert of the present invention balances air pressure in a closed environment. It includes a frame that defines a slot. A pair of tabs emanates from opposing sides of the frame to attach the frame to a door. Media, which has a plurality of apertures therethrough, resides in the slot. The frame, with media installed therein resides within a notch in an edge of a door. Air is permitted to flow through the door insert to balance the air pressure within an environment divided by the door. The frame is preferably ABS plastic and the media is preferably paper. The appearance of the frame and media may be modified to aesthetically match the decor of the door, door hardware and surrounding environment.

Abstract: The fan speed control circuit and system of the present invention includes a capacitor or internally triggered triac to enable current to flow across the terminals of an electrical switch for a fan motor when the switch is in the open and OFF position to permit continued operation of a fan so that the system complies with the ASHRAE 62.2 standard. The capacitor may be of a fixed value so that the speed of the fan motor is reduced to a fixed level when the switch is open and OFF. Alternatively, a potentiometer and internally triggered triac arrangement may be used to permit adjustment of the level to which the speed of the fan drops to when the switch is actuated to the open and OFF position. The present invention is a viable less expensive option to prior art microprocessor based fan speed control circuits.

Abstract: An automatic programmed ventilation control system for operating a fan includes a fan drive circuit; a duty, cycle control circuit including means for selecting a duty cycle and means for setting the selected duty cycle; a timing circuit including means for selecting the time of day and means for setting the selected time of day; a fan speed control circuit including means for selecting a fan speed and means for setting the selected fan speed; and a manual override switch circuit for overriding the set duty cycle and fan speed for operating the fan at a predetermined speed for a preselected period of time.