The two buttons must be pushed at the same time and are located at a distance from each other that prevents simultaneous operation by one hand. The operation should be designed so that if either or both of the buttons are released, the hazardous action of the machinery and/or equipment cannot be reached, or if it can be reached, the mechanism returns to a safe state.
When using fall-arrest systems, specialist assistance may be necessary to select appropriate equipment, provide effective training in use and inspection, and develop an emergency retrieval plan to recover a person suspended in a fall-arrest harness. People suspended by a fall-arrest harness for short periods of time may suffer serious health effects, or may have incurred injury during the fall prior to the fall-arrest device deploying.
Selection and use of PPE requires careful consideration, as there are many different types that reduce the risk of injury of contact or exposure to a hazard. Incorrect use of PPE, or purchasing inappropriate PPE, can contribute to serious workplace incidents. PPE that is uncomfortable, restrictive or heavy may create secondary hazards, and, as a result, constant supervision may be necessary to ensure it is used effectively.
Accidental start-up, or movement of a machine mechanism, can occur: • if control levers or buttons are bumped or knocked • if a short circuit of the control system occurs • when hydraulic or air pressure is released • when undoing retaining bolts. The word machine is derived from the Latin word machina. The modern meaning of the word is influenced due its specialized application in the military siege engines. They are also used in the stage engines, which are used in theater.