The dosage of a chemical, usually expressed as milligrams of the chemical per kilogram of body weight of the test animal, at which 50 percent of the test animals die within a specified time frame
NFPA 1150 Standard on Foam Chemicals for Fires in Class A Fuels, 2004 ed. http://www.nfpa.org/Assets/files/AboutTheCodes/115 0/1150-F2009-ROC.pdf, (Std: Foam Chem for Fr in Class A Fuels - Amer) {387 NFC}