Gas exchange is when oxygen is transferred from the air in the lungs to the blood and carbon dioxide is transferred from the blood to the air in the lungs. It occurs in the alveoli of the lungs.The lungs have 5 main specialisations to allow efficient gas exchange:1. A large surface area for more gas exchange to occur over.2. A moist surface to dissolve gases and increase their rate of diffusion.3. Thin walls so that gases diffuse over a shorter distance.4. A large blood supply so that steep concentration gradients for carbon dioxide and oxygen to diffuse down are maintained. 5. Ventilation through breathing to remove carbon dioxde and bring in new oxygen. This helps maintain steep concentration gradients for both gases.