Key People: Joseph Priestley (Show more) nitrogen dioxide, inorganic compound, a highly reactive and poisonous gas. Nitrogen dioxide is one of several nitrogen oxides (NOx), including nitrous acid and nitric acid, and is often used as an indicator for the larger group of nitrogen oxides. Pungent and extremely volatile, the gas is a dangerous air pollutant associated with fossil fuel combustion. In industry, nitrogen dioxide is an intermediate in the manufacture of nitric acid and a powerful oxidizing agent utilized in chemical processes and rocket fuels. Nitrogen oxides, including nitrogen dioxide, are formed when combustion temperatures are high enough to cause molecular nitrogen in the air ...(100 of 542 words) Access the full article Help support true facts by becoming a member. Subscribe today!