Portable extinguishers are not designed to fight large or spreading fires. Even against small fires, they are useful only under certain conditions:
- The operator must know how to use the extinguisher.
- The extinguisher must be within easy reach, in working order, and fully charged.
- The operator must have a clear escape route that will not be blocked by fire.
- The extinguisher must match the type of fire being fought. (Extinguishers containing water are unsuitable for use on grease or electrical fires.)
- The extinguisher must be large enough to put out the fire. Many portable extinguishers discharge completely in as few as eight to ten seconds.