Checked the oxygen? Good. Checked for explosive atmosphere? Good. But it might still not be enough. Back in 2001 the Britannia P&I Club’s Riskwatch published a cautionary tale of a ship carrying Indonesian crude coconut oil from Kuala Enok to Rotterdam.
A heater in the tank of coconut oil ensured that the cargo remained liquid n the colder climes of Europe.
After berthing and discharge six men went into one of the tanks to clean residue from the pump suction. Oxygen levels were found to be acceptable and tested with an explosimeter showed that the atmosphere was below the lower explosive limit, LEL, so the tank was ‘safe’ and the men started work.
After a while one of the men seemed to be having a problem. Four men managed to get out of the tank, two others collapsed, one of whom later died.
During the voyage from Indonesia the heating of the coconut oil led to the evolution of carbon monoxide gas, something not realised before. indeed, a chemist in the investigation was sceptical until laboratory tests revealed that heated vegetable oils could, indeed, produce carbon monoxide.
The levels in the tank were more than 1,000 parts per million, dangerously high. Carbon Monoxide is deadly because it replaced oxygen in the blood. Think of it as chemical suffocation.
In a previous post we talked of dangerous videos that suggested that it was okay to go into atmospheres of less than 21 per cent (actually, 21.9 per cent). We warned that if the oxygen level was low it was because something was displacing the oxygen and that something might be hazardous. In this case, carbon monoxide was a little more than 0.1 per cent.