Pneumatic weapon

A pneumatic weapon is a weapon that fires a projectile by means of air pressure, similar in principle to the operation of pneumatic tube delivery systems. The term comes from a Greek word for "wind" or "breath" (πνεῦμα).

Comparison with firearms
In theory, pneumatic weapons have certain advantages over traditional firearms:
 * The ammunition can be much simpler (and thus more compact and lighter for the same payload), because there is no need for a propellant or casing; the entire round becomes the projectile.
 * Since no propellant is fired, there is no chemical residue to accumulate in the barrel or chamber.
 * Because there is no casing to eject, it is theoretically possible to have a higher rate of repeat fire.
 * The barrel is not heated to nearly the same extent as with a firearm.

In practice, pneumatic weapons are not as well-developed as traditional firearms and have a number of practical deficiencies:
 * The weapon has to supply or be supplied with a source of very high pressure air, such as a compressor, which adds substantial complexity and weight to the weapon.
 * The action, or the mechanism by which subsequent rounds are automatically reloaded, must also be powered by the air pressure; many modern firearms re-use the energy from the propellant to accomplish this (see Maxim gun), further reducing the amount of work the weapon itself has to do.

Pneumatic weapons in the toy industry
The low projectile speed requirement of a toy weapon greatly reduces the amount of air pressure needed; combined with the importance of safety in the toy industry, this has led to widespread adoption of pneumatic firing mechanisms in toy weapons, where a propellant reaction is not appropriate (although other technologies, such as rubber bands, can be used).

The toy industry has produced a number of pneumatic toy weapons, which fire small, lightweight (often plastic and frequently hollow) projectiles at relatively low speeds. Airsoft and paintball guns are a popular toy that operates this way; when used with adequate safety equipment (eye protection at a minimum) these may be used in games involving shooting at other players.

BB guns and other low powered air guns, while often marketed towards the youth market, are not toys; the steel and lead projectiles they fire can readily penetrate the skin, and are capable of producing lethal wounds. While a lethal wound is unlikely due to their low power, air guns and BB guns should be used with the same precautions as firearms; eye protection for the shooter, a safe range, and an adequate backstop.