According to the 2005 annual survey carried out by the Air-Conditioning and Refrigeration Institute (ARI) on chiller manufacturers, the replacement and conversion of CFC chillers, as specified by the Montreal Protocol in 1995 is proving to be slower than expected in the US. Over a period of 10 years, 46 703 units, i.e. 58% of the 80 000 CFC chillers in use in the US at the end of 1995, have been either replaced or converted. However, the pace of this phase-out has been slower than expected, partly due to federal tax laws which require depreciation of the chillers over 39 years, thus ensuring a steady demand for non-CFC units for at least another decade. An estimated 37 300 CFC chillers using mostly CFC-11 or CFC-12 refrigerants remain in service.