Barium oxide should not be released environmentally; it is harmful to aquatic organisms.
Zinc oxide | Calcium oxide | Nitrous oxide | Tin oxide | nitrogen oxide | barium | Titanium oxide | Magnesium oxide | Sulfur oxide | Silver-oxide battery | Silicon oxide | Ruthenium oxide | poly(1,4-phenylene oxide) | Nitrous oxide engine | Nitrogen oxide | magnesium oxide | Iron oxide | Exhaled nitric oxide | Cobalt oxide | calcium oxide | Barium |