Mothballs are stored in air-tight bags made of a non-reactive plastic such as polyethylene or polypropylene (other plastics may be degraded or softened). The clothing to be protected should be sealed within airtight containers; otherwise the vapors will tend to escape into the surrounding environment.[1] Manufacturer's instructions regularly warn against using mothballs for any purpose other than those specified by the packaging, as such uses are not only harmful and noxious, they are also frequently considered illegal.[2][1]