Abstract: A return air pressure relief vent comprising a baffle structure having two ports, disposed in a partition between two volumes of air and including a plurality of passages that each encompass a straight line extending between the two volumes of air, the plurality of passages structured and arranged to accommodate a pressure balancing flow of air between the two volumes of air while restricting the passage of sound and light.

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.