Many factors can spoil the sample before testing as well, exposing the sample to heat or direct light may cause some of the electrons to dissipate, causing the item to date younger.
Because of these and other factors, Thermoluminescence is at the most about 15% accurate.
Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. It takes 5,730 years for half the carbon-14 to change to nitrogen; this is the half-life of carbon-14.
After another 5,730 years only one-quarter of the original carbon-14 will remain.
The technique often cannot pinpoint the date of an archeological site better than historic records, but is highly effective for precise dates when calibrated with other dating techniques such as tree-ring dating.Thus dating that particular tree does not necessarily indicate when the fire burned or the structure was built.