An important component of residential and commercial ventilation systems is bathroom exhaust fans. Ventilation fans help keep bathrooms, showers, tubs and spas smelling clean and fresh. They also help to prevent the buildup of bacteria that is normally associated with excess humidity. There are several different types of bathroom fans including fan only, fan with LED light, heater, and motion or humidity sensors. For a bath fan to be effective depends on its CFM or airflow rating. Large rooms require a fan with a high CFM or several fans to be installed. Another factor is the sound emitted or the level of measured sones. For a bathroom fan to be considered quiet or ultra quiet means that it has to emit 1.5 sones or less.