While the disk amplifier is operated, the aerosols originating from the decomposition of organic material exposed to flash lamp light is inevitable, which can cause the disk contamination and damage consequently. The nitrogen gas purging is routinely employed to re-achieve the slab cavity cleanliness, which is fundamentally required for disk amplifier reliable performance. The influence on aerosol dissipation by swirl is measured, demonstrating that the desirable cleanliness can not be achieved simply by prolonging the purging time or adjusting the flowing rate as plenty of aerosol is slaved in swirl. So we propose the aerosol dissipation by intermittent purging. The decaying of aerosol concentration is achieved rapidly by repeated dilution as the swirl is destructed time after time. The comparative experiment is carried out at a Φ130 mm disk amplifier specially. After intermittent purging, the residual aerosol concentration in slab cavity is 1/100 of that after a continuous but longer purging. The slab cavity environment cleanliness remains lower than level 40 in the following 15 h, which is much more desirable to prevent neodymium glass from contamination and damage.