A cap sterilizer (50) includes an infeed chamber (52), a sterilant atomizing chamber (53), and an air rinse chamber (54). At least the infeed chamber (52) and the air rinse chamber (54) are exhausted. Both an exhaust pressure (E2) in the infeed chamber (52) and an exhaust pressure (E4) in the air rinse chamber are higher than an exhaust pressure (E3) in the sterilant atomizing chamber (53), or the sterilant atomizing chamber (53) is not exhausted.