1. Measurement of nitrogen oxides

1.1 Properties

Nitrogen oxides consist of all chemical species in which nitrogen is bonded to at least one oxygen atom and whose oxidation number is at least 2. These are NO, N ₂ O ₃ , NO ₂ , N ₂ O ₅ , the corresponding acids HONO and HNO ₃ , and numerous organic nitrates, of which PAN (peroxyacetyl nitrate CH ₃ C(O)OONO ₂ ) is the most abundant. Nitrogen oxides are emitted during the high-temperature combustion of fossil fuels....