July 30, 1997
August 17, 1992
The Environmental Protection Agency (EPA) recently issued an Alert concerning the fire hazard from carbon adsorption deodorizing systems.
Activated carbon systems used to adsorb vapors for control of offensive odors may pose a fire hazard when used for certain types of substances, if proper procedures are not followed. In particular, crude sulfate turpentine, commonly produced in the pulp and paper industry, can pose a fire hazard if the adsorption system is not properly designed and proper procedures are not implemented. Facilities should take precautions to minimize this fire hazard.
In a 1995 accident at a chemical terminal facility, a fire and explosion occurred involving three tanks of crude sulfate turpentine. The tanks were connected to drums of activated carbon for deodorizing. The fire and explosion damaged other storage tanks, resulting in the release of toxic gases and forcing a large-scale evacuation of area residents.
Fires have occurred in the past in activated carbon systems used for deodorizing crude sulfate turpentine. In general, such fires have not had collateral effects on the scale as those reported in the 1995 fire. Large scale collateral effects would not be expected if fires are confined to the activated carbon containers and do not spread to tanks containing flammable or combustible substances.
Activated carbon is widely used to adsorb vapors to prevent their release to the air. For certain classes of chemicals, reaction or adsorption on the carbon surface is accompanied by release of a large amount of heat that may cause hot spots in the carbon bed. Such chemicals include organic sulfur compounds (e.g., mercaptans), which may be found as impurities in crude sulfate turpentine and other materials. Other classes of chemicals that may cause large thermal releases are ketones, aldehydes, and some organic acids. Adsorption of high vapor concentrations of organic compounds also can create hot spots. If flammable vapors are present, the heat released by adsorption or reaction on the surface of the carbon may pose a fire hazard (e.g., a fire may start if the temperature reaches the autoignition temperature of the vapor and oxygen is present to support ignition).
The potential for fire in carbon adsorption deodorizing systems may increase at night. At certain times (typically during the day), high temperatures may lead to the expansion of vapor in the systems, and vapor is likely to exit to the atmosphere. When temperatures drop (typically at night), a slight vacuum may be created, causing air to be drawn into the system. If the carbon surface is very hot, because of the heat generated by adsorption, air drawn in over the carbon may provide the oxygen to start a fire.
Facilities should be aware of the potential fire hazards of activated carbon systems for absorbing flammable vapors and take steps to minimize these hazards. Actions that may help to prevent fires include:
APPLICABLE OSHA STANDARDS
For additional information about the fire hazards of activated carbon adsorption systems and methods of minimizing them consult the following.
1 The Directorate of Technical Support issues Hazard Information Bulletins (HIB) in accordance with OSHA Instruction CPL 2.65 to provide relevant information regarding unrecognized or misunderstood health hazards, inadequacies of materials, devices, techniques, and safety engineering controls. HIBs are initiated based on information provided by the field staff, studies, reports and concerns expressed by safety and health professionals, employers, and the public. Bulletins are developed based on a through evaluation of available facts and in coordination with appropriate parties.
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