Catenary life line. A horizontal rope between two fixed anchorages, independent of the work surface, to which the lanyard is attached, either by tying or by means of a sliding connection. A catenary life line must be capable of supporting a minimum dead weight of 5,400 pounds per person, applied at the midpoint of the line.

Contaminant. Any material which by reason of its action upon, within, or to a person or object is likely to cause physical harm.

Dropline. A vertical rope from a fixed anchorage, independent of the work surface, to which the lanyard is affixed or tied.

Fixed anchorage. A secure point of attachment, not a part of the work surface, for droplines, lifelines, catenary life lines, or lanyards. The fixed anchorage and its appurtenances must be capable of supporting a minimum dead weight of 5,400 pounds per worker.

Lanyard. A rope, suitable for supporting one person. One end is fastened to a safety belt or harness and the other end is secured to a substantial object or a safety line.

Lifeline. A rope, suitable for supporting one person, to which a lanyard or safety belt (or harness) is attached.

O.D. Optical density and refers to the light refractive characteristics of a lens.

Radiant energy. Energy that travels outward in all directions from its source.

Safety belt. A device, usually worn around the waist which, by reason of its attachment to a lanyard and lifeline or a structure, will prevent a worker from falling.