Temporary refuge test (TR testing)
Air leakage and associated risk to TR
The TR provides protection from credible fire and explosion scenarios and has some sealing function to prevent excessive air outflow and ingress of toxic smoke and gases. In the event of smoke detection, the TR heating, ventilation and air conditioning (HVAC) dampers are designed to automatically close, leaving the TR as a sealed unit. In practice, it is not possible to achieve complete air-tightness and various leakage paths exist in the TR fabric through which contaminants can enter. The leakage paths in the shut-down TR can be classified as either purpose provided such as openings for ventilation, doors, windows or unintentional such as leaks, or mere leakages because of errors in design, construction malpractices and degradation as the structure ages.
Temporary refuge is required to prove a defined performance standard in the event of any major mishap on offshore platform. This includes integrity of TR façade from preventing ingress of toxic gaseous elements such as CO2, CO, H2S, NOx, SO2 and so on.
One of the most dangerous and challenging gas is hydrogen sulphide (H2S). Since the gas is heavier than air, it tends to accumulate at low-lying area. Even at low concentrations, H2S can affect the eyes as well as the respiratory tract. The gas is extremely poisonous and, at concentrations over 1000 ppm, people die immediately. And hence, in the event of H2S contamination, fresh air is drawn from higher levels and it is passes through the filters and then it is pressed into TR compartment.