The effectiveness of CO2 is dependent on the interaction between at least three processes:
The effect of pressure is particularly significant. Only the combination of CO2 and pressure allows the treatment to work well in a short period of exposure. For example, in the case of the dried fruit moth, treatment time decreased from 64 hours at a pressure of 3 bar to just a few minutes at 37 bar.
Neither a high nitrogen pressure, comparable with the pressurised CO2 process, nor high CO2 concentrations at atmospheric pressure, achieves the desired effect. It takes around 28 days exposure to kill weevils using pressureless CO2 treatment.