What does fogging of the oxygen mask indicate?

Fogging of the oxygen mask indicates that the patient has started breathing. When a patient inhales and exhales, the warm air from their breath comes into contact with the cooler surface of the mask, causing condensation to form on the inside of the mask. This is a clear sign that the patient is actively breathing and indicates some level of respiratory function.

The other scenarios do not lead to fogging. A loose mask would not create fog but rather risk insufficient delivery of oxygen. Low oxygen supply would not necessarily cause fogging, as it pertains more to the flow rather than the air temperature differences. A damaged mask might imply air leaks but wouldn’t directly correlate with the fogging effect observed when breathing occurs within a properly functioning mask.