The NOAA CFC-12 scale was updated in July, 2009. The new scale (NOAA-2008) is based on a total of eight standards prepared in 2005 and 2008. Standards were prepared by weighing aliquots of pure CFC-12 vapor and pure CFC-12 liquid and diluting with know amounts of CFC-12 free air. Standards prepared from pure vapor and pure liquid show remarkable agreement. The new standards are much more consistent than those that defined the 2001 scale.
To update to the 2008 scale, use the following equation:
Y = 1.0021 * X + 5.807
Where Y is CFC-12 on the 2008 scale, and X is CFC-12 on the 2001 (or 1997) scale.
The new scale is 1.3% higher than the previous scale at 540 ppt.
The following standards comprise the 2008 CFC-12 scale.
|Cylinder||Prepared (ppt)||Assigned (ppt)||residual (ppt)|