system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - If fire extinguishers are supposed to be directed at the base of the fire, why do large fires often have firefighters on extended ladders shooting water from above?
gpt
Fire extinguishers and water used by firefighters are not the same. 

Most fire extinguishers are ABC dry chem extinguishers. They have a chemical powder that disrupts the chemical reaction of burning. So disrupting the reaction needs to occur as close to the source of the fire as possible. 

Firefighters use water. The water in liquid form hits whatever is burning absorbing its heat energy and converting to steam. Raining down water and getting coverage, even on things that aren’t burning, cools the material, creates steam, and absorbs energy. There is also the consideration that large streams of water have the force to penetrate burning material.