The U.S. Department of Energy (DOE) has funded trace gas enrichment experiments since the mid 1990s in two separate programs (the Terrestrial Carbon Processes Program and Program for Ecosystem Research). These experiments fall into two categories, Free-Air Carbon Dioxide Enrichment (FACE) experiments and open-top chamber (OTC) experiments. DOE initially funded the FACE sites as research and development experiments which later evolved into environmental research user facilities. The DOE Biological and Environmental Research Program (BER) operates four distributed research facilities referred to as FACE facilities.
Brookhaven National Laboratory (BNL) supports central operations for several of the FACE sites. Additionally, the DOE supports OTC experiments in conjunction with the Smithsonian Environmental Research Center (SERC) in Maryland and Florida. These sites are part of a larger international FACE network. Please follow this link for more information on site locations and contacts.