News Emergency gas leak gets the all clear in Copper Cliff SHARE ON: Taylor Ablett, staff Thursday, Aug. 13th, 2015 A level three emergency has been called off in the Sudbury area. A hazardous gas leak from the Vale plant prompted the order to have everyone stay inside, and shut off their air conditioning. But, the gas has since dissipated and it is now safe for everyone to go outside. It took almost three hours for it to be safe. The gas was Nitrogen Oxide and Nitrogen Dioxide, which can cause breathing problems or can even be fatal. There are no reports of any injuries.