Abstract: An apparatus for impregnating tobacco with an expansion agent includes a chamber for confining a charge of tobacco under elevated pressure conditions. An accumulator connected to the chamber maintains a supply of an expansion agent in fluid form under conditions of elevated temperature and pressure but less than the desired tobacco impregnation temperature and pressure. The expansion agent is forcibly and rapidly moved from the accumulator and introduced into the chamber under conditions such that the pressure and temperature of the expansion agent are increased to the desired impregnation temperature and pressure, preferably including a pressure approaching or above the supercritical pressure thereof.