Since 1990, there have been more than 60 workplace fatalities due to explosions and fires from hot work activities on tanks. In seven of the 11 accidents discussed in a Chemical Safety Board bulletin, no gas testing was performed prior to or during the hot work activities. In the remaining cases, monitoring was conducted improperly.

In July of this year, new Chairman and CEO of the CSB Dr. Rafael Moure- Eraso, said he was saddened by news of the death of a Colorado welder while performing what is called “hot work” on a storage tank containing flammables at an environmental remediation company in Englewood, Colo.

Hot work is defined as welding, cutting,grinding, or other spark-producing activities that can ignite flammable substances. To date in 2010, the CSB has learned of 15 serious hot work-related fires and explosions that caused six reported fatalities and numerous injuries.

“I am saddened by this accident and disturbed that such fatalities continue to occur,” said Dr. Moure-Eraso. “The CSB is vitally concerned about hot work accidents and this was expressed in our important safety bulletin and safety video, both issued within the past few months.”

According to information gathered by the CSB, a worker was standing on a ladder, welding on the side of a tank partially filled with a mixture of water and flammable hydrocarbons. Sparks ignited flammable vapor and the worker was thrown off the ladder, suffering fatal injuries.

The company said that although it has a hot work permit system and had provided safety training to the victim, there was no monitoring for a flammable atmosphere before or during the welding. While current OSHA standards prohibit hot work in an explosive atmosphere, OSHA does not explicitly require the use of combustible gas detectors.

“There is no secret to preventing these accidents,” said Dr. Moure-Eraso. “Companies should require effective monitoring of the atmosphere before and during all welding or other sparkproducing activities near tanks that may contain flammable liquids or gases. Monitoring should be frequent or continuous and performed at multiple locations to assure that no flammable vapor is present which could be ignited. Monitoring the atmosphere and following the other six key lessons in our bulletin can help avoid these tragedies.”

The CSB safety bulletin is titled “Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks,” and subtitled “Effective Hazard Assessment and Use of Combustible Gas Monitoring Will Save Lives.” It recommends the following:

1. Use Alternatives – Whenever possible, avoid hot work and consider alternative methods.

2. Analyze the Hazards – Prior to the initiation of hot work, perform a hazard assessment that identifies the scope of the work, potential hazards, and methods of hazard control.

3. Monitor the Atmosphere – Conduct effective gas monitoring in the work area using a properly calibrated combustible gas detector6 prior to and during hot work activities, even in areas where a flammable atmosphere is not anticipated.

4. 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.

5. 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.

6. Train Thoroughly – Train personnel on hot work policies/procedures, proper use and calibration of combustible gas detectors, safety equipment, and job specific hazards and controls in a language understood by the workforce.

7. Supervise Contractors – Provide safety supervision for outside contractors conducting hot work. Inform contractors about site-specific hazards including the presence of flammable materials.

The importance of these lessons is evident upon review of 11 accidents briefly described in the bulletin. While each lesson will reduce the likelihood of a catastrophic hot work accident, the CSB says special attention should be paid to Key Lessons #2 and #3 – the importance of analyzing the hazards and utilizing a combustible gas detector to monitor for a potential flammable atmosphere.

These safety lessons are not new; the Environmental Protection Agency (EPA) in 1997 issued a Chemical Safety Alert warning of recent serious aboveground atmospheric storage tank accidents involving flammable vapor explosions, a number of which were ignited by hot work.

The EPA recommended hazard reduction measures that included improved hazard assessment and “proper testing of the atmosphere for explosivity.”

While the OSHA standard prohibits hot work in an explosive atmosphere, it does not explicitly require the use of a combustible gas detector. However, other good practice guidance documents from the National Fire Protection Association (NFPA), American Petroleum Institute (API), and FM Global stress the need for gas monitoring to prevent fires and explosions.

For example, NFPA 326 requires the use of gas detectors when conducting cleaning, repairs, or hot work on or inside tanks and containers that hold or have held flammables. (All 11 accidents described in this bulletin involved hot work in, on, or near tanks that contained flammables.)

Gas testing must be conducted “before and during any hot work, cutting, welding, or heating operations.” If the LEL rises to 10 percent, NFPA 326 requires that all work shall be stopped and the source of the flammable atmosphere located and eliminated or controlled.

For the cases described in this bulletin, an appropriate safety management system, including an analysis of the hazards and the proper use of a combustible gas detector, would likely have alerted workers to the presence of a flammable atmosphere before disaster occurred.

The 11 incidents are divided into two categories: 1) those cases where no gas monitoring was conducted; and 2) those where gas testing was improperly conducted. FSM