Patrons go below ground to play cards, sleep, exercise and work on laptops--all the while inhaling air that can have 1, 700 picocuries of radon per liter (about 1, 300 times as much as air in the average home).

FORBES: Magazine Article

Experiments by Andrew Gallup at Princeton University, his father Gordon Gallup and a colleague found that yawning is suppressed by a cool pack strapped to the forehead or by summer temperatures that are higher then body temperature, and that therefore the purpose of yawning may be to cool the brain by inhaling air.

WSJ: Matt Ridley on Why You Just Yawned | Mind & Matter

Earlier this month, a 12-year-old San Bernardino County girl, Kristal Salcido, died after inhaling Freon from an air conditioner.

NPR: Feds Raid 17 Calif. Businesses For Nitrous Oxide

Rooms with outdoor balconies also make inhaling bellyfuls of fresh ocean- and mountain-cleansed air a morning ritual.

BBC: Business trip: Vancouver