^ ^ "In the two hose structure the exchanged air would not come from the inside on the space or house, but enters with the second hose". Experts123.com. Retrieved 10 June 2015. Clinic operating theatres, where air is filtered to large degrees to cut back infection possibility plus the humidity https://docs.google.com/spreadsheets/d/14Zqd0FEGkdjJlcohp4SFWeSZ9M4AIBFQpIDlHrjqztI