Temperature too can play a significant role. For example, higher temperatures reduce the exposure time. Using pressureless CO2 treatment, exposure time for killing the corn weevil was reduced from 28 days at 10°C to just a few hours at 40°C. However, as high temperatures impair product quality the use of heat is highly problematic. The influence of temperature reduces sharply as pressure level increases. In pressurised treatment, the necessary exposure times do not increase significantly until temperatures of less than 15°C and do not drop again until temperatures of less than 0°C are reached.
Treating products in freezer cells at cryogenic temperatures using liquid nitrogen or liquid carbon dioxide also eliminates insect pests. However, in practice these methods have proven to be not sufficiently reliable due to poor controllability and the condensation of humidity on the post-treatment cold products.
The CO2 content has a significant impact on effectiveness mainly when using the pressureless CO2 method. In this case the atmosphere has to contain at least 90% CO2.
The type of packing and product density have a very high impact on the exposure time. Exposure times increase significantly in the case of compressed goods such as bales, flour sacks or dense bulk goods in big bags. The reason for this is that it takes some time for the required CO2concentration to reach the centre of the packaging. In addition, exposure time is highly dependent on the type of pest and its stage of development. Eggs and larvae exhibit the highest resistance to treatment.