The Chemical Safety Board (CSB)—an independent federal agency charged with investigating serious chemical accidents such as equipment failure, as well as inadequacies in regulations, industry standards, and safety management systems—recently released multiple reports that should be made part of every power plant’s safety training program.

In July, the CSB reported a fatal accident involving a welder performing hot work on a storage tank containing flammable vapors. Hot work—defined as welding, cutting, grinding, or other spark-producing activities—can ignite flammable substances inside empty storage tanks. To date this year, the CSB reports that there have been 15 serious hot work–related fires and explosions that caused six reported fatalities and numerous injuries (Figure 2).

2. Too hot to handle. Hot work on aboveground atmospheric storage tanks filled with flammable vapors caused this explosion that took the life of the welder. The CSB has issued a safety video on the hazard of hot work that should be part of your employee safety training program. Source: CSB

The CSB has released a new 14-minute hot work safety video called “Dangers of Hot Work” that describes how to prevent flammable vapor explosions caused by welding and cutting. Go to the CSB web site ( and search on “hot work video” to download the video for your employee training program.

The CSB has also issued a safety bulletin describing the hazards of hot work. These lessons aren’t necessarily new, given that the U.S. Environmental Protection Agency (EPA) issued similar warnings in 1997 after explosions occurred during hot work in or on aboveground atmospheric storage tanks filled with flammable vapors. Occupational Safety and Health Administration standards also prohibit hot work when an explosive atmosphere is present.

The CSB recently reviewed 11 hot work accidents and previously had published results of its root cause analysis of those accidents. The CSB has also recently identified the common themes that it found in its review of those 11 hot work accidents. Those common threads, listed below, should be part of a plant’s job hazard analysis (JHA). A proper worker safety program should have a JHA review for every task prior to beginning any hot work. Consider the following seven lessons learned:

  • Use alternatives. Whenever possible, avoid hot work and consider alternative methods.
  • Analyze the hazards. Prior to beginning hot work, perform a hazard assessment that identifies the scope of the work, potential hazards, and methods of hazard control.
  • Monitor the atmosphere. Conduct effective gas monitoring in the work area using a properly calibrated combustible gas detector prior to and during hot work activities, even in areas where a flammable atmosphere is not anticipated.
  • Test the area. In work areas where flammable liquids and gases are stored or handled, drain and/or purge all equipment and piping before hot work is conducted. When welding on or in the vicinity of storage tanks and other containers, properly test and, if necessary, continu­ously monitor all surrounding tanks or adjacent spaces (not just the tank or container being worked on) for the presence of flammables and eliminate potential sources of flammables.
  • Use written permits. Ensure that qualified personnel familiar with the specific site hazards review and authorize all hot work and issue permits specifically identifying the work to be conducted and the required precautions.
  • Train thoroughly. Train personnel on hot work policies/procedures, the proper use and calibration of combustible gas detectors and safety equipment, and job-specific hazards and controls in a language understood by the workforce.
  • Supervise contractors. Provide safety supervision for outside contractors conducting hot work. Inform contractors about site-specific hazards, including the presence of flammable materials.

—Edited by Dr. Robert Peltier, PE