Ah very observant young grasshopper, however I have delivered a few in my day and what you cannot see is an exhaust fan drawing the fumes and smoke away from the deck! As you can see the grill has been fired up and the cieling is still white. 
Well, will take your word for it as the ceiling is still nice and white so it must be working! But they better be careful how much booze they serve at the bar. If somebody tips over backward they are going right in the spa!
Of course that may prove to be of some amusement to the other party goers!
