Type I (QCC) connectors have a built-in excess flow feature and a positive shutoff that will not allow gas to flow until the connector is fully engaged. In case of a fire the built-in thermal protection on the QCC connector melts allowing the nipple to disengage from the tank connection and stop the flow of propane. They also provide a positive back check seal at disconnect to eliminate the propane in the hose from being released into the atmosphere.