This book contains a new gas theory. Most of the articles in the meantime published in the open access digital journal "International Journal of Fundamental Physical Science". A new gas theory 'Palchoudhury Gas Theory on outstanding conception 'Exertion of infrared wave force on the outer surface of tiny particle - atoms, molecules etc. and in turn corresponding effects on the inner surface area of a gas container" is established. Palchoudhury gas theory has a profound efficiency to explain all kinds of gas behaviour independently. Independently explained points are the cause of Brownian motion, size of the gas, existence or non-existence of atmosphere in the earth, celestial bodies, size of atmosphere, atmospheric behaviour, thermodynamically conversion etc. It is the most significant, first-time the internal force of gases has been measured. It reveals that the specific heat of a gas is the same in both isochoric (Cv) and isobaric (Cp) process. According to Palchoudhury gas theory, gases never escape from the celestial bodies in space. Palchoudhury gas theory will be helpful for more efficient weather reporting.