Useful features that come with many bathroom exhaust fans include:

• A ceiling light—when the switch is turned on, both fan and light are activated.

• Activation of the fan according to pre-set humidity levels.

• A motion sensor that turns on the fan automatically if someone enters the bathroom and stays running for a pre-determined amount of time.

• A timer switch, which, after it is activated, will keep the fan running for the time indicated, even after the light is turned off.

• An allergen-reducing filter.