Abstract: The invention is a bag opening machine including a perforated drum mounted on a frame for rotation about a substantially horizontal axis. Opposite ends of the drum define a bag receiving opening and a bag discharge opening and a material receiving hopper is mounted on the frame below the drum. A conveyor system transports particulate material filled bags into the drum through the bag receiving opening after the bags have been penetrated by a blade mechanism mounted on the frame. Enclosing the entire machine is a vented enclosure that prevents the migration of dust particles into the surrounding environment. After having been opened by the penetrating blade mechanism, the bags are conveyed into the rotating drum and emptied by the tumbling action therein.