Abstract: A suction excavator including an air pump for generating a flow of air and a nozzle through which air is drawn under the influence of the air pump, the nozzle being arranged when in use to suck up spoil from an excavation, and a mechanism for separating spoil from the air drawn through the nozzle. The excavator is provided with a fuel gas detector to detect for the presence of fuel gas in the flow of air drawn up through the nozzle. When fuel gas is detected a valve may be actuated to interrupt the flow of air up through the nozzle and instead to admit air from a substantially fuel gas free source to flush any fuel gas out of the system reducing the risk of an explosion.