The Australian driller takes off his mask a decent distance away from the poison well fire and dies nearly instantly. Yet Greg is right under the well and has a hole in his hose going directly into the closed environment of his mask and is only knocked out.
However, this can be explained by the Australian breathing air that had been saturated with the poison gas. The gas was spreading past the safety flags, possible due to wind or other weather conditions. Greg was working with an air mask. When his hose split he still had some air left in his tank that would have been at a higher pressure than the outside air, keeping it out of his breathing air to a degree. He is seen putting his hand over the leak and then passing out in the water. The water would have prevented further poisonous air from getting into his system.
