1.1 This specification covers throw-away, flat panel-type filter units for use in air conditioning, heating, and ventilating systems. This specification also includes panel-type filters with pleated media.1.2 The values stated in inch-pound unit This specification covers throw-away, flat panel-type filter units for use in air conditioning, heating, and ventilating systems. This specification also includes panel-type filters with pleated media. The filters are furnished in two types as follows: