Disclosed are apparatus for delivery of a gas, e.g., carbon dioxide and/or chlorine dioxide, and methods of its use and manufacture. The apparatus includes an envelope, and a sachet within the envelope that contains reactant, which generates a gas in the presence of an initiating agent, e.g., water. In another embodiment, the apparatus includes a barrier layer, a sachet layer disposed adjacent to the barrier layer, a reactant disposed between the barrier layer and the sachet layer that generates a gas in the presence of an initiating agent, and an envelope layer disposed adjacent to the sachet layer.
