Function introduction: The disposable breathing filter for lung function test is a filter device connecting the subject and the lung function instrument. The patient's exhaled gas passes through the breathing filter, bacteria, viruses and other pathogens are adsorbed in the filter, which can not only prevent the patient's exhaled pathogenic microorganisms from contaminating the instrument, but also prevent the patient from inhaling the pathogenic microorganisms from the contaminated instrument, effectively avoiding cross infection The occurrence of the same time, while reducing the loss of equipment, improve the efficiency of lung function testing.