The Dustless HEPA wet/dry Vacuum gives you a distinct advantage by enabling you to switch from dry to wet operation without worrying about getting the valuable HEPA filter wet. A protective baffle/wall inside the canister protects the HEPA filter from water. One of the big advantages of the Dustless HEPA wet/dry Vacuum is the optional Micro Pre-filter that greatly extends the life of the HEPA filter. The Micro Pre-filter is an inexpensive disposable filter that captures the vast majority of the dirt and dust before it reaches the more expensive HEPA filter.