Many businesses must install and maintain backflow prevention devices. Common examples are manufacturing facilities, process plants, medical facilities, restaurants, laboratories including school chemistry and biology labs), and buildings with boilers, fire sprinkler systems and irrigation systems. Usually residential facilities are exempt from the rule unless a specific cross-connection is identified. For example, single-family residences with a lawn irrigation system require backflow prevention. Multi-family residences with a boiler or fire sprinkler system require backflow prevention.