Gross Alpha and Gross Beta Concentrations:  The total radioactivity due to alpha or beta particle emission.  Gross analyses are generally made first to determine the total amount of radioactivity, of a certain type, that is present.  The more extensive specific analyses of beta- and alpha-emitting isotopes are only made if the gross measurements are above background levels.

Iodine-131:  Charcoal cartridges are analyzed for gamma emitting radionuclides, specifically Iodine-131.  Iodine-131 is of great interest because it is produced in relatively large quantities by nuclear fission and has a half-life of only eight days.  This means any Iodine-131 that is detected would be from a recent release of fission products.  The charcoal cartridges are analyzed in batches.  Because of this batch testing, results from several locations may be the same.