For use in plume rise calculations, wind speed should be measured at stack top or 100 m whichever is lower. Ideally, the wind speed sensor should be mounted on a tower located near stack base elevation.

Great care should be taken to ensure that the tower is not sheltered in a closed valley (this would tend to over-estimate the occurrence of stable conditions) or placed in a location that is subject to streamline compression effects (this would tend to underestimate the occurrence of stable conditions).