Abstract: An automatic temperature responsive assembly for ventilating through a roof a confined space to the atmosphere whereby heat buildup in the confined space may be released from the confined space or fresh air permitted to enter therein. The assembly comprises housing means adapted to be coupled to the roof of the confined space and having an opening extending therethrough with cover means operatively associated with the housing means and mounting means operatively associated with the housing means for pivotally securing the cover means thereto, so as to be movable between a generally open position and a generally closed position for enclosing the opening. A temperature responsive drive assembly is mounted to detect temperature changes in the confined space and adapted to actuate in response to temperature changes within a predetermined range, and camming means is pivotally secured relative to the housing means and including a camming surface thereon for engaging the drive assembly.