This is the area or space where the gas exchanges take place, It should have a larger surface-to-volume ratio, moist inner surface, and thin wall in contact with blood capillaries.
External gills, internal gills, lungs, and the insect tracheae all can function as respiratory surfaces.
Gaseous exchange in the lungs takes place between alveoli and alveolar blood capillaries.
The respiration surface in humans is the alveoli.
Because it has all the characteristics of a good respiratory surface, so efficiency is more.