Tar smells for a long time because volatile smoky and oily compounds continue to leave the material slowly, especially when the tar is warm, fresh, thick, or indoors.
The smell of tar comes from many small volatile compounds, not from one single ingredient. Wood tar can smell smoky and resinous. Coal tar can smell heavier and more industrial. Different tars smell different because they come from different raw materials and production methods.
Long smell comes from slow release. A tar coating may form a surface skin while softer material underneath still holds volatile fractions. Warmth lets those fractions move and evaporate. This is why old tar can smell again on a sunny day or when an object is brought into a warm room.
Thickness matters. A heavy layer in cracks, rope, or rough timber can hold smell far longer than a thin brushed coat. Enclosed spaces also concentrate odour because the air is not carrying the vapours away.
Persistent smell is normal for many tarred materials, but it should be taken seriously when the product is industrial, solvent-based, creosote-like, or intended only for outdoor use. The type of tar matters as much as the strength of the smell.