Abstract: An enclosure is arranged for mounting within a framework of an associated window to permit a pet to be received within the enclosure to permit access to fresh air when the pet is maintained within an interior environment in a dwelling. The enclosure is arranged to be formed with spaced side walls and an end wall, with each of the walls having a screen member mounted therewithin. The invention in modified form may include window plates pivotally mounted above each screen member and may be further provided with a heating assembly to provide heating within the enclosure during periods of depressed temperature conditions.