How old is an adult in first aid?

In terms of providing first aid to an ''adult'', it is usually made on a subjective judgment of the casualty's size rather than age. A child is usually classed as up until puberty and an adult may be classed as after that.

For example in CPR, 'child' CPR should be followed for children up until age 12 (approx) but 'adult' CPR can safely be administered to casualties above this age. It is usually made on judgment and there is no definite age limit.