Not to be confused with the international chemical company of the same name, the Köln-based duo of Cem Oral and Ingmar Koch (who go by the names Jammin' Unit and Walker, respectively) have been making hard-hitting experimental acid and techno as Air Liquide since the early '90s. Recording first for their own Structure label group before signing with Rising High in 1993, the pair currently record for the New York-based Smile Communications, as well is in various side projects for labels such as DJungle Fever, Anodyne, Blue Angel, and Oral's own Pharma imprint. Although the pair have dabbled in everything from beatless ambient to back-breaking, nosebleed gabber, the bulk of their material has clustered around dirty, mid-tempo acid and breakbeat techno, with the focus on thick 303 lines and simple, minimal phrases. They've also increasingly moved to a more hip-hop-infused brand of caustic electro, with tracks appearing on Rising High's Further Self-Evident Truths label compilations and the Coldcut Journeys by DJ mixed CD.

Koch got his start in the music industry on the far side of the integrity line, pumping out assembly-line house and hip-hop for the German Hype! and Technoline labels, before the latter went bankrupt in the early '90s. He then headed for university, studying electronic composition and attempting to break the bad habits he'd picked up in mainstream production. It was then that Koch met Oral, a member of the same German underground scene that included J. Burger, Mike Ink, and Biochip C.'s Martin Damm. Together the group consolidated their efforts toward assembling the influential Structure label group, which included the Structure, Monotone, Blue, and DJungle Fever imprints. With releases running the spectrum from ambient, house, and techno to acid and hardcore, Koch and Oral's work together began to coalesce into a coherent sound reflecting shared influences such as Chicago acid, early New York hip-hop, and '70s prog experimentalists such as Neu! and Can.

Soon after Structure dissolved into the various labels and projects of its key participants, Walker and Jammin' Unit signed the Air Liquide name to the English Rising High label, through which they released a number of well-received full- and EP-length albums, including Liquid Air, Nephology, and Weather Machine. The pair also recorded for Smile. Walker continued to release material on his own Pharma label, as well as through DJ Ungle Fever, Analog, and others. Oral released several solo albums as Jammin' Unit, for Rising High and Blue Planet. ~ Sean Cooper, Rovi