Risk minimization in isolated subsurface structures through ventilation induced by natural forces

The subsurface infrastructure contains solitary structures and complex networks interconnected by piping or duct. These structures meet generally accepted criteria for classification as confined spaces. Fatal incidents continue to occur through mechanisms often not recognized or appreciated until follow-up study. This paper reviews some of the recent fatal incidents that have occurred in order to identify actions needed to minimize the risk posed by hazardous atmospheric conditions in the airspace. Consistent, optimized ventilation in isolated subsurface structures not entered for a long period of time induced by natural forces minimizes development and persistence of hazardous atmospheres. A logical venue through which to pursue these actions is the Prevention through Design (PtD) initiative of the National Institute for Occupational Safety and Health (NIOSH). This paper recommends research to discover and understand the means by which ventilation of these structures induced by natural forces occurs and application of engineering principles to the design and placement of openings in manhole covers and hatches to achieve optimization. These outcomes are believed capable of considerably reducing risk to workers from exposure to the internal atmosphere during preparation for entry and work in these structures, to passersby exposed to emissions through openings in manhole covers and hatches and to everyone from risk of explosion.