Robert Barry, Untitled, August 1967.
Robert Barry, Inert Gas Series/Hélium, Neon, Argon, Krypton, Xenon/From a Measured Volume to Indefinite Expansion, 1969.

Inert Gaz Series: Helium. Sometime during the Morning of March 5, 1969, 2 Cubic Feet of Helium Released into the Atmosphere.
