The paper provides insight into why (for liquid wastes) 'puffs' are very easily generated and why their magnitudes and intensities increase with increasing kiln temperature and rotation speed; and how the generation of puffs in general is controlled by waste properties, sorbent properties, and kiln operating parameters. A theoretical model describing simultaneous heat and mass transfer into a sorbent aggregate, coupled with vapor-pressure-driven waste vaporization within the sorbent aggregate, was combined with a fragmentation model and was able to qualitatively predict experimentally observed effects relating to puff duration, kiln speed rotation, kiln temperature, and stoichiometric oxygen requirement of the waste. These theoretical results support data from an EPA rotary kiln incinerator simulator.