A fire extinguisher is a crucial safety device used to control or extinguish small fires, often in emergency situations. It is not designed for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user (i.e., no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire brigade. Typically, fire extinguishers consist of a handheld cylindrical pressure vessel containing an agent that can be discharged to extinguish a fire.