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RR997 - Modelling smoke and gas ingress into offshore temporary refuges

The Cullen report into the Piper Alpha disaster recommended that a temporary refuge (TR) should be provided on all offshore installations. The TR is required to have a defined performance standard related to its survivability when exposed to a major accident that includes, but is not limited to, ingress of smoke, flammable and toxic gas.

Current guidance on risk assessment for TRs focuses on the demonstration of TR integrity. This can be interpreted as demonstrating that the TR will remain unimpaired for sufficient duration as to allow corrective action and/or evacuation to be planned in the event of an accident.

This report sets out a model for determining TR impairment times arising from the ingress of smoke, flammable and toxic gas. The method is based upon leakage data from pressure testing and using the methods set out in the supporting document to HSE HID Semi-permanent circular SPC/Tech/OSD/30. The method is a staged approach that uses established calculation methods to determine the air change rate using the pressure test data, the infiltration of gases into the TR and the physiological effects of these gases.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

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Updated 2013-11-21