It has recently been demonstrated that the earth's atmosphere has still not reached equilibrium.
C14 in the atmosphere would eventually reach equilibrium.
Willard Libby, the inventor of carbon dating, did some research on equilibrium in the atmosphere.
This is why some really wild numbers have appeared, for example, a freshly killed seal was carbon dated to be 1300 years old, and shells from living snails were carbon dated at 27,000 years old.
Evolutionists will argue that these wild dates come from a phenomenon of "old carbon" in the water on the ocean floor, and that's a reasonable argument, but there's a serious logical problem with it that most evolutionists won't consider.
One cannot even conceive of how such a task could be accomplished with mankind's limited ability, and that is for something we can see (e.g.
grasshoppers), let alone what is invisible to the naked eye (e.g. No consistent amount of C14 has ever been calculated in the atmosphere, nor is it possible for mankind to do such a thing without having a device that, at minimum, spanned the circumference of the atmosphere.
Radioactive carbon, as mentioned earlier, forms in the atmosphere from radiation striking nitrogen, and that radiation is randomly introduced into the atmosphere. Also, I have had evolutionists personally tell me that it is impossible to know for sure because the earth's magnetic field fluctuation also effects how much radiation comes through the atmosphere, so there again, the constant for C14 in the atmosphere today is a complete uniformitarian assumption.
In addition, even if it were possible to test for a constant level of C14 in the air, it would not be possible to test and prove that all life had the exact same amount.
If we turned on a garden hose and used that constant rate of water to fill up a barrel, but I drilled holes in the side of the barrel, the hose would begin to fill up the barrel, but as the water got higher, more of it would begin to leak out.