Improved Scent

(Savage Species, page 36, DnD 3.0)

[General]

You can detect and track creatures by smell at greater distances than normal.

Prerequisite

Scent ability

Benefit

You can detect approaching enemies and sniff out hidden foes within 60 feet. For strong scents, such as smoke or rotting garbage, double these ranges. Overpowering scents, such as skunk musk or troglodyte stench, can be detected at triple normal range.

Normal

Without this feat, you can detect creatures by smell only within 30 feet.