2012 Chevrolet Cruze smoke under the hood when using the heat

Why when using the heat, smoke comes underneath the hood on the left side and Burt fumes comes inside the car?

I suspect that a heater hose (after the heater valve) has a small leak. You MUST immediately check your antifreeze level when the engine is cold. Check both the reservoir and open the radiator cap. You do not want to drive if a leak is possible.