Hello and Thank you for choosing Just Answer. My name is XXXXX XXXXX X will be the Mercury Expert assisting you out today.
Smoke coming out of the vents is usually the indication of a blown heater core inside the heater box. The heater core is a small radiator type looking part that gives the heat to the cab of the car. When it leaks, coolant will leak into the box and then this will cause the smoke or steam from the vents.