Safety Margins on a Rebreather

There used to be a time when there was no safety margin in any activity that the human being wanted to participate in. In a merciless prehistoric world, on a daily basis, the cave men were hunting with stones and sticks, a large variety of predators the size of a truck, expecting to feed a hungry family. Then, Winchester gave men the ability to kill wild animals while staying at a comfortable distance, without risking their lives. Safety margin was born.