A paintball marker, also known as a paintball gun, is the central or main piece of equipment in the sport of paintball. Markers make use of an expaning gas such as carbon dioxide, compressed air or nitrogen dioxide to propel paintballs through the barrel. The paintball community generally prefers to use the term "marker" rather than "gun" in order to mitigate the public perception that paintball markers are weapons, and that paintball is a dangerous sport. The term derives from its original use as a means for forestry personnel and ranchers to mark trees and wandering cattle.