All ventilation systems are designed to prevent the buildup of indoor air pollutants and make your house a healthier place to live, but they can vary from simple exhaust fans to high-tech, whole-house air systems. Your choice depends on your air quality and whether you are looking for a minimum or maximum solution. The range-hood exhaust fan is a prime example of a simple solution. It removes a lot of air for short periods of time on demand. It is used together with a whole-house system for areas like kitchens, bathrooms, and workshops. Adding a fresh-air duct to the return air plenum of the furnace is better than relying on cold-air drafts to replace the air the exhaust fans throw outdoors. An air-change ventilator does the same thing more efficiently. Usually a single box with two fans, it moves air both into and out of the house. A heat recovery ventilator (HRV) does the same job but also traps most of the heat from the exhaust air and uses it to warm up the fresh air coming in, saving significantly on heating costs. A new breed of ventilation system, the energy recovery ventilator (ERV), also uses exhaust heat to preheat the fresh air but brings back some of the moisture to maintain a good humidity balance in houses that become too dry with continuous ventilation, recuperating even more heat and eliminating static electricity.