2 NH3 + 4 O2 --> 2 NO + 3 H2O
2 NO + O2 --> NO2
2 NO2 + 1/2 O2 + H2O --> 2 HNO3(aq)
... scheme proposed by Intel and others is an example. So are several laws proposed or already enacted in various jurisidictions (State, Federal, non-US). Most would include ...