Lesson Learned Statement:When performing HEPA filter changeouts, the hazard analysis should consider environmental protection as well as worker protection. This is especially important for old and deactivated facilities.
Discussion:During an effort to replace last-in-line HEPA filters, the potential for environmental impacts was not considered significant since the system would be isolated during the filter change. Last-in-line filters have no other filters between themselves and the stack. However, in an attempt to provide more protection to the workers, a decision was made to leave a slight crack in the isolation valves so that a slight negative pressure would be maintained in the filter house. Thus the potential for material to be released from the filter housing and the potential for exposure to the workers in the immediate area would be minimized.
The HEPA filter replacement was being performed in a deactivated facility where the filters had not been replaced by the current work force. Additionally, the unusual down flow design of the filter system allowed contamination to easily fall into the "clean" side of the housing.
Analysis:Factors to be considered during hazard analysis that will minimize the potential for insult to the environment include knowledge of the filter house configuration and the position of filters with regard to the effluent stack. If the filters are the last-in-line, controls such as placing dampers on the exhaust side in the closed position and independently verifying their positions, should be implemented to prevent the discharge of contaminated particles through the stack. When assessing the filter house configuration, hazard analysis should note whether the direction of airflow is upward or downward. If the airflow moves in a downward direction through the filter bank, contaminated particles may fall out during filter removal and settle into the bottom of the filter housing. Controls should be implemented to ensure that the housing is vacuumed to remove loose particles before new filters are installed and the system is put back on line. This will also reduce the potential for contaminated particles to be released.
Originator:Bechtel Jacobs Company; Sylvia Wright, (865) 241-5052; RCWM Project
Contact:Joanne E. Schutt, (865) 483-0554
Name Of Authorized Derivative Classifier:J. Larry McNelly
Name Of Reviewing Official:D. C. Lannom
Priority Descriptor:Yellow / Caution
Keywords:HEPA filters; last-in-line; filter changeouts
References:Occurrence Report ORO-BJC-X10ENVRES-2002-0012
Occurrence Report ORO--ORNL-X10BOPLANT-2002-0007
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DOE Function / Work Categories:Environmental Protection - General
Maintenance - Facility
Maintenance - HVAC
ISM Category:Analyze Hazards
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