No, radiation is not gas, at least not the nuclear kind. Nuclear radiation is generally divided into two kinds: particulate and electromagnetic. Neither of them is gas. It might be argued that alpha...
Carbon dioxide
Oxygen
Oxygen is used for breathing. Our body cells then use this oxgen to produce energy (glucose), and give off carbon dioxide which is breathed out again!
http://wiki.answers.com/wiki/Neon (Ne) is an inert gas sometimes used in deep http://wiki.answers.com/wiki/Commercial_diving but is very...