Incense, Scentbane

Source Advanced Race Guide

Scentbane incense is a form of smokestick that also blocks most scents. As long as the smoke lasts, creatures with the Scent special ability must make Perception checks, opposed by the Stealth checks of any creatures within the smoke, to use Scent to locate creatures within the smoke. If a creature remains in scentbane incense for 5 rounds or more, the smoke clings to it for 1 round after it leaves, making it similarly difficult to find by Scent during that time.