Abstract: Disclosed is a large scale mobile positive pressure blower designed to provide positive pressure ventilation for fighting fires in large spaces such as tunnels, mines, halls, warehouses large Box stores, high-rise buildings, shopping malls and the like. In accordance with the invention, a hydraulically or electrically operated ventilation blower is provided on an adjustable elevation device that may be mounted either on a movable vehicle or trailer, or in stationary locations in the vicinity of a structure opening or portal. The blower delivers a large volume of air having a conical shape into an opening at one end of the structure (e.g. a transportation tunnel) to force the smoke and hazardous gasses out through a different opening. One or more blowers may be used, depending upon the size of the entrance and the structure.