During the Holiday House Tour, a few people commented on the hook in the center of the kitchen lighting fixture at the Hexagon House. Before the chandelier’s transition to electricity, the hook likely held a smoke bell to catch any soot from burning the oil or gas fuel before it could stain the ceiling.
Although not identical to the chandelier at the Hexagon House, you can see a number of gas fixtures with smoke bells in the National Park Service’s Gaslighting in America book. Plate 82 in particular is quite clear. Still not convinced? There is one other smoke bell installed downstairs at the Hexagon House. You can view this smoke bell at close to eye level by partially climbing the stairs to the second floor.