Coalition forces in Iraq have used white phosphorus in both illumination rounds and in smoke-producing ones. This is standard, everyday warfare stuff.

White phosphorus can be used in incendiary rounds which are to be used against targets such as buildings.

They are neither "chemical weapons" nor "anti-personel" rounds.

Illumination shells are set to activate at a certain elevation so that they drift slowly downward, with the help of a fire-proof parachute, and illuminate the battlefield.

If such a shell were to fired directly into a building, it would not trigger the elevation sensor and would not activate.

Smoke rounds could be fired into a building to injure occupants, but this is not an authorized use. Those ordering such actions woud be in some trouble with the brass.