61.   It has also required them to add a new test to detect nitrogen oxide, alongside the familiar tailpipe probe, which measures carbon monoxide and hydrocarbons.

62.   It would emit half the nitrogen oxide allowed under the current national standard and one-third the hydrocarbons.

63.   It uses a catalytic combustor to burn a lean fuel mixture at a temperature below that at which nitrogen oxides, a component of pollution, are produced.

64.   Just this spring, standards were tightened again, for nitrogen oxides.

65.   Low-sulfur gasoline emits reduced amounts of nitrogen oxides, which in turn lower ozone levels.

66.   Most of the plants meet existing federal limits on the chemicals, nitrogen oxides, and are in areas that do not exceed smog standards.

67.   New cars have catalytic converters, which reduce carbon monoxide and nitrogen oxide.

68.   New diesel engines that burn a fuel that is lower in sulfur would cut nitrogen oxide and other harmful emissions.

69.   Nitrogen oxide, or NOx, is also a common pollutant from the burning of coal, gasoline and other fossil fuels.

70.   Nitrogen oxides are blamed for causing lung-searing smog.