Dating uses the properties of atoms
It is typically released to the atmosphere in the form of carbon dioxide at BWRs, and methane at PWRs., radioactive carbon dioxide.
The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale in the order of weeks).
Libby estimated that the radioactivity of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram of pure carbon, and this is still used as the activity of the modern radiocarbon standard.
These amounts can vary significantly between samples, ranging up to 1% of the ratio found in living organisms, a concentration comparable to an apparent age of 40,000.), or other unknown secondary sources of carbon-14 production.The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate.--or rather, its relative absence—is therefore used to determine the relative contribution (or mixing ratio) of fossil fuel oxidation to the total carbon dioxide in a given region of the Earth's atmosphere.