A comparison of measured respirator protection factors for a di-2-ethylhexyl phthalate (liquid aerosol challenge) respirator quantitative fit test method is made with a complementary sodium chloride (solid aerosol challenge) method. The United States Army XM-29 chemical warfare defense respirator was used in this evaluation. A subject pool of twelve individuals (two female and ten male) were fitted and tested on both respirator quantitative fit test methods on ten different occasions. An exercise protocol of six different breathing and head movement maneuvers was used in each test. The purpose of the comparison was to determine if there is a difference between the two fit test methods. The di-2-ethylhexyl phthalate method showed a significant order-interaction effect with respect to the exercise sequence and whether it preceded or followed testing with sodium chloride. The sodium chloride method did not show a similar phenomenon, and consistently measured smaller protection factors compared to the di-2-ethylhexyl phthalate method. It appears that the sodium chloride method is more sensitive.