CO2 rockets are a very safe and simple way to experiment with model rockets. Most CO2 rockets are very small and do not travel very high or fast. The common method of construction for a CO2 rocket is to take a CO2 canister and use it as the motor to propel the projectile, or load into the air.
Construction
The construction of a CO2 rocket can either be very easy or very difficult depending on the method used to build the launch pad, the cargo or payload module, the firing mechanism and the aerodynamics of the bomb.
The simplest way to build a CO2 bomb is to fine-tune the CO2 tank from an Airsoft launcher and implement it into the bomb as the bombfire. The launch pad is perhaps the most difficult part of the process.
References
CO2 rocket Wikipedia(Text) CC BY-SA