The Bosch downdraft ventilation system is the perfect companion to your Bosch electric or gas cooktop. When needed, the unit rises up a full 9 inches from the rear of the cooktop. Steam and cooking odors are drawn through the 5 layer stainless steel filters by a powerful fan and then vented outside. The fan can be located in the rear of the cabinet or placed on an outside wall or roof. The electronic controls offer many options, including: 3 fan speeds, delayed shutoff and even a reminder to let you know when to clean the filters (dishwasher safe). When not in use, the unit quietly retracts and "disappears" behind the cooktop. This makes it the ideal choice for island applications. Without a large canopy or exposed chimney, you are able to maintain an open kitchen style.