What percentage of oxygen does a BVM deliver if not connected to supplemental oxygen?

When a bag-valve-mask (BVM) is not connected to supplemental oxygen, it relies on the ambient air in the environment to deliver oxygen to the patient. Ambient air has a composition that is approximately 21% oxygen. Therefore, when a BVM is utilized without any supplemental oxygen, it delivers a mixture of ambient air which contains around 21% oxygen. This is the basis for understanding the effectiveness of a BVM when oxygen is not supplied; it functions primarily by ventilating the patient with the air available in the surroundings.

This knowledge is crucial for first responders as it emphasizes the importance of connecting the BVM to supplemental oxygen whenever possible to increase the percentage of oxygen delivered to the patient, especially during respiratory emergencies.