Pouches and the stick-on appliances to which they attach must be changed regularly. Sometimes an odor neutralizer and lubricant is squirted into a new pouch before it is attached. Two types of pouches are available: one disposable and one drainable. Most pouches are opaque and filter out air through a charcoal filter. The recommended practice is to empty such pouches when one-third full. Appliances, in contrast with pouches, are usually replaced every three to seven days except in cases where their seals have broken contact with the skin, when they should be replaced immediately.