SIM 3/2007/11. Prevention of fatal and major injuries through safe interventions project Read on…

In 1997 a Joint Industry Programme (JIP) was undertaken on “gas build-up from high pressure natural gas releases in naturally ventilated offshore modules”. As a consequence of the JIP, a workbook was created. The workbook aims to provide a quick, first pass, technique for estimating the flammable volume arising from the release of a material within a confined, and congested, naturallyventilated offshore module.

However, the workbook has not, to HSE’s knowledge, undergone independent assessment of its scientific basis. Neither does it appear that its performance has been evaluated against offshore measurements or the results of more detailed modelling. Hence its range of applicability and predictive capability are not well understood.

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The risk of exposure of workers to contaminants in indoor spaces is usually assessed by measuring or predicting the level of indoor air concentration in the absence of workers. The amount of contaminant likely to have been inhaled by a worker is then deduced from the value of indoor air concentration obtained at the position where the worker is normally standing. However, it has been shown that the value of airborne concentration measured with a sampler fixed at the position where the worker is but in the absence of the worker can be lower than the one recorded with a personal sampler. This is due to the heat released by the human body, which can be sufficient in some circumstances to generate upward velocities near the body and lift the contaminant up to breathing height.

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