air-tight

ilmatiivis (alternative form of)
1895, H. G. Wells, The Time Machine Chapter X

Further along the gallery was the huge skeleton barrel of a brontosaurus. My museum hypothesis was confirmed. Going toward the side of the gallery I found what appeared to be sloping shelves, and clearing away the thick dust, I found the old familiar glass cases of our own time. But these must have been air-tight to judge from the fair preservation of some of their contents.