The successful completion of three major engineering tasks required of the Free Air Carbon Dioxide Enrichment (FACE) Facility Development Project in 1989 is discussed. The first, toe relocate the entire experiment from Yazoo City, Mississippi, where it was conducted in 1987 and 1988, to Maricopa, Arizona went according to schedule. The second, documentation of the reliability of the facility over a complete growing season, showed that the three critical exposure rings operated properly for better than 96% of the treatment period. The third task was to determine the system's ability to maintain the carbon dioxide concentration in each ring at a given set point. An analysis of carbon dioxide concentration data collected once each minute at the tip of the canopy in the center of each exposure array showed that over the entire treatment period, the one-minute average CO₂ concentration at the center of each ring was within 20% of the set point of 550 ppm for more than 97% of the time, and within 10% of the set point for greater than 86% of the time.

In summary, the system as implemented in 1989, met its design criteria for ease of relocation, reliability of its components, and ability to maintain a set carbon dioxide concentration over its entire period of operation. The successful operation of this design during the past few years under climatic extremes, from winter in New York to summer in Arizona, suggests that it would be suitable for studying many plant communities both managed and natural.