A faulty gas-monitoring sensor is believed to have contributed to an incident in which 18 workers were exposed to a potentially deadly gas at a copper and zinc mine near Millertown, Newfoundland.

At about 8:05 pm on January 4, a half-hour into the night shift, employees of the Duck Pond Mine were working 250 metres below surface when one miner reported smelling gas, says Larry Bartlett, human resources superintendent for mine owner, Teck Cominco Ltd.