!!! BE SAFE - CO2 AND HIGH PRESSURE CAN BE VERY DANGEROUS !!! !!! ATTEMPT AT YOUR OWN RISK !!! To prevent this, test everything before firing, be sure the rocket slides freely in the pipe. You can drill small holes at the base of the pipe to prevent gas buildup and get a cool smoke effect. The rocket is DIY so you might have to play with the design and printing process a little bit. It's built to house a 12g CO2 cartridge used for BB Guns