PURPOSE: To decrease the time needed for refrigerating the objective agent which used, e.g. for maintaining freshness of perishable foods.

CONSTITUTION: This agent is piled up in a perforated corrugated fiberboard box having at least one pair of openings installed on side walls facing each other and through spacers smaller than the bottom area of the box, and the box contg. the agent is subjected to refrigeration. A corrugated fiberboard is suitable as the spacer.