The photochemical smog does not generally contain

The major components of photochemical smog are nitrogen oxides, ozone $\left({O}_{3}\right)$, $PAN$ (peroxyacetylnitrate), and chemical compounds that contain the-$CHO$ group (aldehydes). $PAN$ and aldehydes can cause eye irritation and plant damage if their concentrations are sufficiently high.

Classical smog occurs in a cool, humid climate. Its components include smoke, fog and sulphur dioxide. It is reducing in nature.