A case of carbon monoxide poisoning occurred in the late morning at an open-pit quarry while water was being pumped into a flotation tank of a mining barge. The pump was being powered by a generator that had been placed inside the tank. A technician inside the tank told a co-worker outside the tank that he was having trouble breathing. The co-worker then went down into the tank and found the technician lying unconscious. He alerted the site’s other employees. The quarry foreman helped him to remove the unconscious technician from the tank. Alerted by the employees, the firefighters resuscitated the unconscious technician by giving him oxygen. All three men were taken to hospital: the victim by helicopter and the foreman and other technician by ambulance.

The generator usually used for this operation was not usable because its power cable was not long enough. The technicians had placed a smaller generator directly inside the tank without considering that exhaust gases would build up. The accident was caused by the use of a generator in a confined space.

After the accident, the operator added a confined space entry permit to its procedures so that such work can be carried out safely. It installed a carbon monoxide detector in the tank. It also improved the conditions for emergency access to the barge by acquiring an additional boat and water rescue equipment. Finally, it improved its alert and communication system.