Vent restriction devices will not function as which of the following measures when using coaxial Stage I Vapor recovery?

Vent restriction devices are specifically designed to regulate the flow of vapor and air in the context of vapor recovery systems, particularly during fuel transfers. Their primary function is to maintain a balance in the tank's vapor space and prevent excessive pressure or vacuum that could lead to tank damage or emissions during fueling.

In the context of coaxial Stage I vapor recovery systems, these devices are not intended to serve as overfill-prevention measures. While they help manage vapor and maintain safety by providing backup through pressure relief, they do not directly prevent the physical act of overfilling a tank. Overfill prevention typically requires different technologies or mechanisms that can detect fluid levels and stop the pumping process before a tank becomes full.

Backup safety systems and spill containment, on the other hand, have dedicated roles in maintaining overall safety and compliance during fuel handling. Thus, the inability of vent restriction devices to function as overfill prevention highlights a limitation in their specific application within vapor recovery systems.