When someone is involved in a fall, it is essential to have a pulley system available for retrieval. Without them, it would be extremely difficult to lift up someone who has fallen, be it from any height. Pulley systems will usually have a 4:1 or 5:1 lifting ratio, making heavier loads easier to lift. Pulleys become particularly significant in confined spaces where only a limited number of people can enter and only with the proper equipment. Pulley systems are then used to bring up the workers that have fallen, or overcome by poisonous gases back to the surface.