From my visits to the dome headquarters and research the only thing that could possibly offgas is the polyurethane insulation which is buried beneath 2-3" of the concrete. The concrete is on the inside of the the dome: then the polyurethane insulation: then the outside "bubble" shell made of PVC. Not sure how much offgassing polyurethane experiences.

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"Its not a matter of being ready as it is being prepared" -- B. E. J. Taylor