Air-Cooling Roots Vacuum Pump Relying on a suitable gas circulation inherently controlled by a cooler fitted outside, the series ZJQ roots pumps can be operated continuously for over-coming very high pressure differential without being overloaded. Also can be operated with its exhaust pressure atmospheric gas. They own excellence of the general roots pump. They can be operated singly, also can be operated combining with backing pump. When the pump is operated singly, the exhaust pressure atmospheric gas can cool the pump and a cooler is unnecessary, an ultimate pressure of approximate 130hpa at the inlet side can be attained. The series ZJQ roots pumps can be operated in series and also be operated combining with normal roots pumps to make they bring feature of clean pump housing into full play. They can also be combined with backing pumps such as liquid ring pumps or rotary piston pumps to make themselves have a higher pumping speed near main pump even in higher pressure range and get different ultimate pressures from 105pa to 5×10-5pa. Because of their high capacity, the series ZJQ roots pumps are widely used in many engineering fields requiring to be exhausted rapidly and low ultimate pressure or requiring to be exhausted cleanly and no oil pollution.