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Didn't remember it off the top of my head, but Google is our friend. This was the first article up when I searched on "Pompeii carbon dating calibration." Turns out to be about Argon-Argon rather than carbon 14, but it gives the idea.

Radiometric Dating Methods.

Recent experiments on volcanoes of known ages have been done using the 40Ar/39Ar dating method, which seem to confirm its accuracy. Recent testing of volcanic material from Mt. Vesuvius was dated accurately with the 40Ar/39Ar method to within seven years of the actual event.3 40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger was written by P. R. Renne et. al. and published in Science 277: 1279-1280 (1997). Renne tested Ar-Ar dating by checking it against the 79 A.D. eruption of Vesuvius that destroyed Pompeii. Renne and his team noted that “Analysis of single crystals, for example by laser fusion, can obviate xenocrystic contamination, but single crystals are seldom large enough to yield measurable quantities of 40Ar* through radiogenic ingrowth in the Holocene [i.e. last 12,000 years].” Would Ar-Ar dating methods work such recent material? It apparently did. The testing returned an age of 1925±94 years. The true age was 1918 years. The test was off only 7 years. The conclusions of Renne and his team read as follows:
Thus despite the presence of excess 40Ar, a sample less than 2000 years old can be dated with better than 5% precision, validating 40Ar/39Ar dating as a reliable geochronometer into the late Holocene. These results also demonstrate that excess 40Ar can be identified in volcanic sanidine, and while perhaps negligible in pre-Holocene rocks, it has important consequences for sample at the limit of the method’s applicability. Further improvement in precision of 40Ar/39Ar analysis of historically dated samples may lead to welcome refinements in the ages of neutron fluence monitors, currently a limitation on the accuracy of the 40Ar/39Ar method. Our results also substantiate validity of the 40Ar/39Ar method in establishing the eruptive histories of populated active volcanic regions, where such information is vital to volcanic hazard assessment.

Note that this kind of thing, from what I quoted earlier, is prime creationist out-of-context quote salad material.

“... [S]ingle crystals are seldom large enough to yield measurable quantities of 40Ar through radiogenic ingrowth in the Holocene [i.e. last 12,000 years].”
--- Evolutionist P. R. Renne, Science 277: 1279-1280 (1997)

Interesting, thanks! And yes, Google is our friend. I never thought of searching for phrases like that.

Thanks again.