Sub-slab Pressure Field Extension in Schools and Other Large Buildings

The most direct method of projecting or measuring the performance of an active soil depressurization (ASD) system is to measure the strength and extent of the pressure field established under the slab. The pressure field extension (PFE) can be determined during diagnostics to help design an ASD system and following installation to ascertain system performance. In schools , and other large buildings, these data are invaluable to provide a system which will mitigate the building without undue cost escalation. This paper presents EPAts experiences using PFE to design ASD systems for old and new schools, including instances where the data collected resulted in the installation of smaller systems than expected and selection of high vacuum fans instead of "normaltu mitigation fans. A central collection system for use under very large slabs is presented, and PFE data for a hospital under construction are presented. This paper has been reviewed in accordance withe the U. S. Environmental Protection Agency's peer and administrative review politics-and approved for presentation and publication.