ABSTRACT
O), nitric oxide (NO), nitrogen dioxide (NO
), nitrogen trioxide (N
O
), and nitrogen pentoxide (N
O
), that are referred to collectively as NO
. The two oxides of nitrogen that are of primary concern to air pollution are NO and NO
. NO is a colorless gas that is a precursor to NO
and is an active compound in photochemical reactions that produce smog. NO
is a reddish brown gas that gives color to smog and can contribute to opacity in flue gas plumes from stacks.
