Summary: Not many of us have carefully considered the necessity for fire extinguishers. We typically think that simply fighting fire with water is enough but that is incorrect. One of the stuff we need to think about is that we're not terribly certain if there are combustible materials that may worsen the spread of fire. Flammable liquids float in water and may help in the spread of light liquids caught aflame. Fire extinguishers have different compositions that are made to put off fire straight away. It is always most sensible to have one so you can be certain you've got to use in time of need.
