The altimeter setting of 29.92 is used to calculate the Mode C (or Mode S) pressure altitude transmitted by the aircraft's transponder to ATC.
Pressure altitude is based solely on the difference between the ambient pressure at your aircraft's altitude and the standard sea-level pressure (29.92 inHg). It is not affected by the altimeter setting the pilot enters in the cockpit.
Therefore, even if you accidentally left your altimeter set to 30.22, your transponder would still report the correct pressure altitude based on 29.92 inHg, and ATC would see no difference.
This is an important distinction: the altimeter setting in the cockpit affects the altitude you see, but it does not influence what ATC sees on their radar scope.
The altimeter setting of 29.92 is used to calculate the Mode C (or Mode S) pressure altitude transmitted by the aircraft's transponder to ATC.
Pressure altitude is based solely on the difference between the ambient pressure at your aircraft's altitude and the standard sea-level pressure (29.92 inHg). It is not affected by the altimeter setting the pilot enters in the cockpit.
Therefore, even if you accidentally left your altimeter set to 30.22, your transponder would still report the correct pressure altitude based on 29.92 inHg, and ATC would see no difference.
This is an important distinction: the altimeter setting in the cockpit affects the altitude you see, but it does not influence what ATC sees on their radar scope.