My 2012 Kia Optima has been making, what I can only explain as a puff of air noise immediatly after shutting the engine off. What could this be, is it safe to drive?
Air equalizing in the intake manifold? Is this new?
Yes, I’ve never noticed it before! Today is the first day I’ve heard it. Is it ok to drive for a few days until I can get it looked at? I have 2 little kids…cars make me very nervous 
but thanks for the reply
abs systems during a self-test can make a sort of rumbling noise, so it could be that. the actuator motors for the hvac system can continue to make noises after the car is turned off, another idea. brake power boosters could do that, which could indicate they are faulty. you might also try the forum search feature here. type in “puff” etc into the search box, click that icon above right that looks like a magnifying glass. I seem to recall other posts on similar symptoms.
Did you ever resolve this issue? My 2012 Kia Optima is doing this too. Any info would be greatly appreciated!