Mothballs are small balls made from chemicals which repel moths. They are used to prevent moths from chewing on garments and other things placed in storage, ensuring that these items will be in good shape when someone is ready to use them. Many hardware stores sell mothballs, as do some department stores and home supply stores. Mothballs should be stored in a sealed container at all times, as they can be hazardous to human health.
Camphor was historically used to make mothballs, but modern mothballs are made from naphthalene or paradichlorobenzene. In all cases, these chemicals emit a very distinctive strong odor as they sublimate from a solid to a gaseous state. The gas will kill moths and their larvae, ensuring that they do not colonize items in storage. Studies on mothballs have suggested that they may be carcinogenic, so people should be careful around them.
For mothballs to work, they must be kept in a sealed container, which will allow the gas to build up. This also is safer for humans and animals in the same house, as they will not be exposed to the gas. When someone wants to use something which has been mothballed in storage, it should be aired for a day or so before being worn or used, to allow the gas to dissipate. This will also help to temper the sharp smell associated with mothballs.
As an alternative to mothballs, some people prefer to use cedar. Cedar blocks, balls, and shavings can all be used in much the same way as mothballs are, except that cedar is not dangerous. For cedar to be most effective, a sealed container is again required, but no airing is necessary before use, and some people actually rather enjoy the distinctive scent of cedar on their clothes, blankets, and other belongings.
Because mothballs are so closely associated with putting things into storage, the term “mothballed” is also used more generally to talk about any sort of defunct project or stored material. For example, a factory may be mothballed when it is no longer in active production, or a project might be mothballed due to lack of interest or funding. In all cases, the assumption is that the project, facility, or object could be restored to full activity at some point in the future.