Lethal Concentration 4 : Medicine. That quantity of a substance administered by inhalation that is necessary to kill 50 percent of the test animals exposed to it within a specified time
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}