The lengths of polymerization induction periods for butyl acrylate (BA) in the presence of air were measured at temperatures from 54 to 122.5 degrees C. The kinetics of MEHQ and oxygen consumption at 80 and 100 degrees C are characterized by their own induction periods followed by sharply accelerated rates immediately prior to the BA polymerization. It is proposed that these phenomena are consistent with an "intrinsic" BA radical formation rate that is extremely slow compared to the ultimate rate of radical production from the decomposition of peroxides. These oligomeric peroxides build up during the induction period and, at its end, rapidly decompose with a resulting "radical cascade effect," causing the accelerated inhibitor and oxygen consumption followed rapidly by BA polymerization. Thus, confirmation that a supply of BA has a normal MEHQ concentration may not be sufficient to ensure its stability. Strict adherence to the storage conditions and shelf life recommended by the supplier(6) is absolutely vital to storage safety, especially because uncontrolled polymerization of BA has the potential to be violent (polymerization exotherm rates higher than 1000 degrees C/min were observed).