The Chemical Safety Board (CSB) released an animation regarding fatal accident occurred at February 8, 2017, where three peoples were killed due to an explosion caused by hot work activities.
Hot work has been the cause of several serious accidents in the industrial environment. Usually, these accidents occur due to failure to follow the hot work best practices and standards, such as: NFPA 51B, 29 CFR 1910.147 (lockout, tagout), 29 CFR 1910.252, etc.
See below the animation provided by CSB, to better understand the accident.