The breathing circuit of anesthesia machine and ventilator is composed of joint, three-way joint and bellows. The joint is made of high-density polyethylene resin material according to GB11115, and the bellows are made of medical soft PVC material according to GB10010. It is divided into three kinds of specifications.Rated flow of the breathing circuit: 30L/min, pressure increment no more than 0.2KPa, the breathing circuit should be aseptic.