Abstract
Facilities with potentially significant toxic and/or flammable hazards often establish shelter-in-place locations (SIPs) in order to mitigate risks associated with an accidental release of hazardous materials. In addition to rapidly isolating the source of a release, typical SIP strategies include isolating building ventilation systems upon detection of dangerous concentrations of hazardous gases at the SIP ventilation intake and making the SIP as leak-tight as possible. However, the reliability of such detection systems and ventilation isolation mechanisms can vary dramatically, as can the leak tightness of SIPs. The adequacy of SIP tightness and the reliability of its ventilation isolation can therefore become sources of debate without any clear resolution. This paper provides guidance for establishing defensible values for these parameters based on standard risk analysis techniques.
An additional concern with SIP designs is that the building may be vulnerable to potential blast damage from vapor cloud explosions, so directing people to a shelter-in-place location may not be as effective as evacuating them to a safe outdoor muster point. This becomes especially pertinent with materials such as hydrogen sulfide which are both flammable and toxic. Issues associated with SIP blast vulnerability, loss of SIP pressurization, temporary loss of boundary integrity due to exterior door opening by “late comers,” and crediting escape packs, self-contained breathing apparatuses, air-supplied respirators and evacuation fallback plans are covered in this paper. SIP design challenges such as methods of creating a leak-tight volume, addressing oxygen depletion and carbon dioxide buildup, providing emergency communication, and development of practical fallback plans are also discussed in this paper.
