602131 A device (10) to seal a container during fumigation is disclosed. It has a gas impervious barrier (12) configured to be located between an opening of a container (16) and a door (18) arranged to close the opening. There is a passageway through the barrier, the passageway providing a pathway between the interior and exterior of the container for a fumigation gas. An outlet to extract the gas is also disclosed. The device is shaped to fill the gap left by the container door when ajar i.e. wedge shaped.