A Bag-Valve Mask (BVM) is a medical device used to provide positive pressure ventilation to individuals who are not breathing or are breathing inadequately. It consists of a self-expanding bag, a unidirectional valve, and a facial mask. The bag is squeezed to deliver air or oxygen to the patient's lungs, while the valve prevents exhaled air from returning to the bag. BVMs are commonly used in emergency situations, such as during cardiopulmonary resuscitation (CPR) or in hospitals. They are essential tools for healthcare providers, including paramedics and doctors, to ensure that patients receive adequate oxygenation until further treatment can be administered.