An airsmith is a gunsmith

Gunsmith

A gunsmith is a person who repairs, modifies, designs, or builds firearms. This occupation is different from an armorer. The armorer primarily maintains weapons and limited repairs involving parts replacement and possibly work involving accurization...

 that services, repairs or modifies airguns rather than firearms. The term is most commonly applied to those who work on paintball

Paintball

Paintball is a sport in which players compete, in teams or individually, to eliminate opponents by tagging them with capsules containing water soluble dye and gelatin shell outside propelled from a device called a paintball marker . Paintballs have a non-toxic, biodegradable, water soluble...

 guns (often called marker

Marker

Marker may refer to:* Marker , a morpheme that indicates some grammatical function* Marker , a special-purpose computer* A set of sewing patterns tightly arranged within a rectangle that is placed over cloth to be cut...

s) but can also apply to those who service pellet guns.

The term "airsmith" may also apply to those who work on Airsoft guns. It, more generally, applies to those who specialize in servicing high-pressure air systems, which can prove extremely hazardous if not professionally maintained or installed. Even mundane fittings can turn into dangerous missiles at extreme pressures, so it is important to ensure anything involving high pressure gas is professionally installed.