CO2 and HPA/Nitro – F.A.Q. CO2 and HPA/Nitro - F.A.Q. In this article, I will discuss the pro's and con's about these two gases and common terminology used. I do hope that this article will help you choose which gas is best for you. CO2 (carbon dioxide)   Stored as a liquid in cylinders and expands into a gas, Cannot ... Read More