My friend Henry Fuhrmann, a copyeditor (subeditor to you lot) on the Los Angeles Times, today posted this image to Facebook:
He noted: “We usually leave the Britishisms to, well, the British. But I like how Mary McNamara used ‘fug’ — meaning the unpleasant air in a crowded room — in her weekend commentary on Bill Cosby.”
The only “fug” I was aware of was the euphemism invented by Norman Mailer in The Naked and the Dead, later picked up by Ed Sanders in naming his ’60s rock band. But sure enough, the OED notes the word is “originally School slang” and provides this definition: “A thick, close, stuffy atmosphere, esp. that of a room overcrowded and with little or no ventilation.” The first citation was an 1888 quote from novelist E.F. Benson: “Seating himself in the most comfortable chair, as a consolation for the prevailing fug.” And there was also the interesting variation “fug-footer,” meaning indoor football and apparently spotted at Harrow in 1884.
Well played, Ms. McNamara!
notoneoffbritishisms.com 
As a Briton, I have to say that’s not quite the way we’d use “fug”, I don’t think … a fug certainly wouldn’t have “bitter glee” in it. It’s more gloomy and stifling and depressing.
From Bertie Wooster’s description of the annual prize-giving at Market Snodsbury Grammar School (“Right Ho, Jeeves!”, P.G. Wodehouse): “There still seemed to brood over its Great Hall not a little of the fug of the centuries. It was the hottest day of the summer, and the atmosphere remained distinctive and individual.”
The few times I’ve seen “fug” in print, I assumed it was related to fugue, which can also imply an air, overshadowing or miasma of gloom or depression, etc, settling over a room or a person’s mood.