bodies. Training is required to include instruction on theoretical aspects of using the equipment, and also practical aspects. Typically a fall protection, sometimes called fall arrest class is 8 hours long for general workers, but may include a second 8 hours of training for workers who climb communication towers, or oil derricks. Fall protection training includes information on the use, maintenance, inspection and hazards of using fall protection equipment. Energy absorption To arrest a fall in a controlled manner, it is essential that there is sufficient energy absorption capacity in the system. Without this designed energy absorption, the fall can only be arrested by applying large forces to the worker and to the anchorage, which can result in either or both being severely affected. An analogy for this energy absorption is to consider the difference in dropping an egg onto a stone floor or dropping it into soft mud. Even for the same fall distance and weight of egg (the input energy), there will be more damage with the stone floor as the arrest distance is smaller and so forces must be higher to dissipate the energy. For the soft mud, the arrest distance is longer and so arrest forces are lower but the egg is still stopped and is hopefully undamaged. Because fall arrest designs require high-rate-energy capacity design methods, fundamental fall arrest design is tedious and esoteric. Thus, most fall arrest parts and systems are designed to the force standards contained in Federal OSHA 29CFR1910.66 appendix c, a force-type design standard which accounts for required energy considerations. The standard mitigates PPE interchangeability problems, allows wide use by designers not versed in high rate energy methods, and it limits the force into the worker to a survivable level. Actual loads on the user and anchor-anchorage vary widely with user weight, height of fall, geometry, and type of line/rope. Excessive energy into the support and user is avoided by the use of energy absorbing PPE designed for the 1800 lbs maximum of the referenced Federal OSHA standard. (Designers should be cautioned that the force values of the standard are based on high rate energy system design and thus its force values are not necessarily inter-related.) The most common fall arrest system is the vertical lifeline: a stranded rope that is connected to an anchor above, and to which the user's PPE is attached either directly or through a "shock absorbing"