Acetylene was a gas used in welding, and sometimes for lighting.
Acetylene could be produced by adding water to carbide, which could then be used to light carbide lamps. (TOS - The Janus Gate novels: Present Tense, Future Imperfect, Past Prologue)
In the 20th century, some torches used acetylene. (TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 1)
In 2265, the air in Vanguard's salvage bay was thick with ozone and acetylene exhaust. (VAN novel: Harbinger)
In 2381, acetylene was used in USS Aventine's engineering to weld critical components back into place. (ST - Destiny novel: Lost Souls)