PURPOSE: To enhance safety at the time of storage by putting sodium bicarbonate into a moisture permeable bag, putting an acidic soln. into a moisture impermeable bag, keeping both bags so as to be housed into an expansion bag in the state of holding both bags in proximity to each other, applying impact to mix the contents therein and expanding this expansion bag by the generated carbon dioxide.

CONSTITUTION: The sodium bicarbonate 2 is sealed into the moisture permeable bag 1 and the acidic soln. 4 into the moisture impermeable bag 3. Both bags 1, 3 are housed into the expansion bag 5 in the state of holding the bags in proximity to each other. The expansion bag 5 is preferably housed within a cylindrical cardboard 6 of a cup shape, etc., sealed in the aperture by ornamental paper pieces 7 expressing leaves, etc. Impact is applied to the expansion bag 5 by striking or pressing the bag with hand, by which the moisture impermeable bag 3 is ruptured to mix the acidic soln. 4 and the sodium bicarbonate 2 in the expansion bag 5 via the moisture permeable bag 1. As a result, the expansion bag 5 is expanded by the carbon dioxide generated in such a manner, by which the object, such as animal (monkey), is exposed outside by displacing the ornamental paper pieces 7.