Abstract: A housing and float assembly allow for vapors or gases displaced during filling storage vessels to be redirected from a normal vent through a vapor or gas activated whistle or alarm without significantly restricting the venting rate of the vessel. The alarm produces a warning for the operator that the storage vessel has reached the predetermined high level to help avoid overfilling of the storage vessel. The device can be fabricated from readily available "off the shelf" parts and mounts into standard pipe threads or on to standard pipe flanges. The device can be provided as a kit to be assembled by the user.