The concentration in air of an extremely hazardous substance above which there may be serious immediate health effects to anyone exposed to it for short periods
Business Continuity Institute BCI, Glossary of General Business Continuity Management Terms, UK 2009. Caversham, http://www.thebci.org/glossary.pdf, http://www.thebci.org/glossary.pdf, http://recoveryspecialties.com/glossary.html, (BzCntMgt - Brit) {17}