Adrexan vapor is a highly combustible gas, which has the appearance of a white fog. Adrexan vapor is kept in high pressure containers, isolated from any sources of combustion and kept at extremely cold temperatures. When it is released from these special containers, it can be absorbed into both metals and biological materials. Once ignited, it burns at extremely high temperatures -- enough to severely damage Leviathan biomechanoids and to destroy Karack metalites.
Adrexan vapor is seen in an episode of Farscape.