The utility model provides a valve, a valve includes the case, the case is connected and is passed through at the exhaust lid that exhaust pipe open -top located with the setting self gravity of caseclose with the process line of exhaust pipe intercommunication, and will the exhaust lid is opened. The utility model provides a valve has realized that the action of flue and gas vent is chain, emergency especially when having a power failure, realize emergency shut down, protective apparatus safety.