Harnett County deputies charged Adam Bailey, of Clayton, with possession of explosives on school property.
Thomas Nathan Minor, 19, of Fuquay-Varina, faces the same charge. He was arrested Friday and made bond Saturday.
School officials said it appeared to be an exam-week prank.
Investigators said an explosive device made of a plastic bottle and chemicals that react when combined caused the fumes. One was placed in the dorm's first-floor hallway and three others outside, authorities said.