A small, flexible, cone-shaped boot that is installed at the base of certain vacuum assist Stage II recovery nozzle spouts to enhance the effectiveness of vapor collection.
Although similar in function to a nozzle bellows, a vapor escape is much smaller and does not provide an airtight seal with the motor-vehicle fill pipe. This device is also called a vapor splash guard or an efficiency compliance device (ECD).
See also PEI/RP500.