Interaction of CO₂ and other factors

The effectiveness of CO₂ is dependent on the interaction between at least three processes:

• Acidification of the insects' cell sap and haemolymph due to higher concentration of dissolved CO₂ in bodily fluids under pressure (formation of carbonic acid)
• Pressure, particularly effective during depressurisation (decompression sickness)
• Oxygen deprivation

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 30 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.