Vitalograph Safe One Way Mouthpieces x 200Vitalograph Safe One Way Valve Mouthpieces Box of 200 The low cost, low resistance Vitalograph SafeTway mouthpiece allows entry of expired air into the measuring system, but not back to the test subject. This simple, yet effective patented design prevents concerns of accidental inhalation of pathogens. The Vitalograph SafeTway is an inexpensive alternative to the bacterial viral filter for expiratory only testing. It fits most pulmonary function test