Why are shut-off valves located 12 inches from the vehicle ends of ac service equipment hoses is it to minimize venting of refrigerant or reduce pressure blow back?

Shut-off valves are typically located 12 inches from the ends of A/C service equipment hoses to minimize the venting of refrigerant during service and to reduce the risk of pressure blowback. This positioning allows for easier access to the valves while ensuring that any refrigerant can be contained more effectively, thereby enhancing safety and efficiency during maintenance. By minimizing the distance from the service equipment, it helps prevent accidental releases of refrigerant into the atmosphere.