The 6300 Blower Door System has three Model 6000 Calibrated Fans in one Large Cloth panel door frame system. It will blow large quantities of air to test Commercial, Multi-Family or High Rise buildings. But has 1 hp fans, not ¾ hp fans found in all other blower door systems. In addition to power, the other advantage is speed stability which is near perfect since it uses variable frequency drives to power the fan motors.