A paintball marker, also known as a paintball gun, paint gun, or marker, is the main piece of equipment in the sport of paintball. Markers use an expanding gas, such as carbon dioxide (CO2) or compressed air, to propel paintballs through the barrel and quickly strike a target. The term "marker" is derived from its original use as a means for forestry personnel to mark trees and ranchers to mark wandering cattle.
The muzzle velocity of paintball markers is approximately 90 m/s (300 ft/s). While greater muzzle velocity is possible, it has been ruled unsafe for use on most commercial paintball fields. When paintballs hit an object at high speed they have the potential to cause damage; a paintball colliding with human skin, even protected by cloth, may cause bruising or further tissue damage. However, the damage depends on the paintball's velocity, its impact angle, whether it breaks, and which part of the body it hits. Because of the potential for serious soft tissue damage, paintball players must wear masks to protect their eyes, mouth, and ears when barrel blocking devices are not preventing paintball markers from firing.
Most paintball markers can be disassembled into four main components: the body, hopper, barrel, and gas system or air tank.
Masks are safety devices players are required to wear at all times on the field, to protect them from paintballs. The original equipment used by players were safety goggles of the type used in labs and wood shops; today's goggles are derived from skiing/snowboarding goggles, with an attached shell that completely covers the eyes, mouth, ears and nostrils of the wearer. Masks can also feature throat guards. Modern masks have developed to be less bulky compared with older designs. Some players may remove the mouth and/or ear protection for aesthetic or comfort reasons, but this is neither recommended nor often allowed at commercial venues.