PAD is a patented product invented by DurkeeSox fabric ductwork company, PAD(pressure adjustment device) is pressure balance device specially applied for fabric air dispersion system, of which material is a kind of special permeable grid material and shape is conical. One end is connected to fabric air duct through concealed heavy-duty zipper and in the other end adjust the cord to change end vent area., so as to adjust pressure distribution in the system. DurkeeSox fabric ductwork patented this structure. In the straight duct of fabric duct system, end static pressure is higher than inlet static pressure due to static regain. Thus pressure is uneven and air supply is uneven no matter at the beginning or at the end.. That is why pressure balance device, PAD is required to install in air duct. PAD change airflow resistance through changing vent area, thus adjust pressure balance between front and back end. The smaller opening of PAD is, the bigger resistance is, and the bigger change in pressure difference is. It has an obvious effect on adjusting pressure balance in the air duct.