Ventilation study for imported containers

This study focuses on prevention of possible exposure to chemical agents, when opening, entering and stripping freight containers. The container degassing process is investigated using tracer gas measurements and numerical airflow simulations. Three different container ventilation conditions are studied, namely natural, mixed mode and forced ventilation. The tests conducted allow degassing time variations to be quantified in relation to various factors such as container size, degree of filling or type of load. Natural ventilation performance characteristics prove to be highly variable, depending on environmental conditions. Use of a mechanically supplied or extracted airflow under mixed mode and forced ventilation conditions enables degassing to be significantly accelerated. Under mixed mode ventilation, extracting air from the end of the container furthest from the door ensures quicker degassing than supplying fresh air to this area. Under forced ventilation, degassing rate is proportional to the applied ventilation flow. Moreover, degassing rate depends mainly on the location at which air is introduced: the most favourable position being above the container loading level. Many of the results obtained during this study can be generalised to other cases of cleaning air in a confined space by general ventilation, e.g. the priority to be given to positioning air inlets or the advantage of generating high air velocities to ensure maximum stirring of the volume.