Carbon monoxide is a relatively nonreactive gas with limited solubility. However, plastic funnels made of nonreactive polyethylene are used for transferring aqueous solutions. This makes it kinetically nonreactive despite being thermodynamically one of the strongest oxidants. To ensure purity, the reactor is evacuated and filled with the nonreactive noble gas argon. Sulfuric acid must be stored carefully in containers made of nonreactive material (such as glass). The sugar moieties are nonreactive and the DNA backbone is not broken. The test is typically termed "reactive" (also "reassuring") or "nonreactive" (also "nonreassuring"). These shapes tend to be made from fiberglass, teflon, and nonreactive metals. Iron that is bound to ferritin in nonreactive. Tattoo inks have been described as "remarkably nonreactive histologically". In its dry, crystalline state it is nonreactive. Divers underwater have reported that great hammerheads tend to be shy or nonreactive toward humans.