Abstract: A chimney cap for closing and venting, selectively, the upper end of the chimney is manually controlled by means of chains or the like from a combustion area, particularly a fireplace, through counterweights and pulleys. Automatic control is determined by a smoke, heat, or incipient fire detector that will operate a hold relay to produce a signal split between a reset timer and double-throw, double-pull switch that is in turn operated by the position of the cap to operate a reversible motor for movement of the cap to its upper vented position upon the detection of combustion products within the chimney. Movement of the cap to its upper position will shield the detector and other electronics from combustion products, and after a timed period, the reset timer will actuate the motor to move the cap to its closed position where it will remain unless the detector again detects the presence of combustion products.