Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Back to the OSAC Lexicon


An unplanned event that interrupts an activity and sometimes causes injury or damage or a chance occurrence arising from unknown causes; an unexpected happening due to carelessness, ignorance, and the like.

Date Added to Lexicon
Standard Source (Designation Number Title of Standard. Publisher, Place, Year.)
NFPA 921:2021 Guide for Fire and Explosion Investigations. The National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA, 2021. Source link