Q. What is it?
A. A solid, waxy manmade substance that smells like garlic, ignites spontaneously at about 86 degrees Fahrenheit, and produces intense heat, bright light, and thick smoke.
Q. What does it do?
A. Exposure may cause burns, skin irritation, and damage to organs or bones. It burns until deprived of oxygen.
Q. What is its primary use?
A. Combat troops use it as a smoke screen to conceal movement and to illuminate large areas.
Q. Did the US military use it in Iraq?
A. The Pentagon admitted last week to using white phosphorus while fighting the insurgency in Fallujah in November 2004, but ''very sparingly" to illuminate combat areas. Military officials now confirm it was used as an ''incendiary weapon," but as a conventional, rather than chemical weapon.
Q. Is that against the law?
A. The use of white phosphorus as a conventional weapon is not outlawed or banned by any convention. The 1980 Convention on Conventional Weapons forbids using incendiary weapons against civilians or against military targets amid concentrations of civilians. The United States did not sign convention protocols.
SOURCES: US Agency for Toxic Substances and Disease Registry, BBC, National Safety Council
Kathleen Hennrikus/Globe staff