Pyridine appears as a clear colorless to light yellow liquid with a penetrating nauseating odor. Density 0.978 g / cm3. Flash point 68°F. Vapors are heavier than air. Toxic by ingestion and inhalation. Combustion produces toxic oxides of nitrogen.Pyridine is an azaarene comprising a benzene core in which one -CH group is replaced by a nitrogen atom. It is the parent compound of the class pyridines. It has a role as an environmental contaminant. It is a mancude organic heteromonocyclic parent, a monocyclic heteroarene, an azaarene and a member of pyridines.