Which gas exist in air that your body needs to survive?
Of all the gases in the atmosphere that you need to survive, oxygen is the one but you also need nitrogen which you don't use like you use oxygen but it does keep your lungs inflated.
Your body needs constant supply of the oxygen in order to survive. If respiratory system stop working, you will die, say within five to seven minutes. Brain needs oxygen constantly. It will stop working and you become unconscious. You will die eventually with out oxygen. (Clean and fresh air is the birth right of every individual. It is denied now a days due to air pollution.)
Food, water, air, and a place to live are all main necessities of life. Without these things life on Earth would not exist. In my opinion the most important necessity would a place to live, because the definition for a place to live is an area that has EVERYTHING an organism needs to survive. This would include food, water, and air.
The air you breath is roughly 80% Nitrogen. But your body can't use the nitrogen directly from the air, so that doesn't do you any good. There are certain bacteria that take nitrogen that gets into the soil the soil and make it into compounds that your body can use, so when you eat plants you can get the nitrogen your body needs. For more information, look up the "nitrogen cycle."
If by "air" you mean Oxygen, yes. All animals (except for that crazy jellyfish they found) needs oxygen to survive. A hermit crab's gills will filter the oxygen (or "air") out of the water. Even land hermit crabs have modified gills that need to stay moist in order to perforn the same task. If their gills dry up, they suffocate.