AstraGuard™ Bacterial / Viral Filter AstraGuard™ (732254_BX) 100/BXThe AstraGuard Bacterial Viral Filter provides virtually perfect infection protection for expiratory and inspiratory spirometry testing This easy to use disposable mouthpiece incorporates a highly efficient woven filter that virtually eliminates cross contamination from patient to patient and from patient to health care professional Low resistance to airflow 99. 9% bacterial and viral efficiency Small, non threatening size