Three methods of applying carbon dioxide to grain stored in silos are described. One method involves purging a full silo from the top, another involves purging a full silo from the bottom, and the third involves introducing carbon dioxide in the grain stream as a silo is being filled. Comparative purge times, carbon dioxide requirements, and costs are given. Modification of storage- facility atmosphere is a promising method to achieve residue-free insect control, and the merits of using carbon dioxide and nitrogen for this purpose are compared.