The nature of lockout/tagout has significantly advanced since the 1970s when the original Z244.1 text was drafted. During the development of 29 CFR 1910.147, OSHA made decisions that altered or added to the intent of the content and meaning of various provisions of Z244.1. One critical decision involved the eventual interpretation and enforcement of the bracketed sentence ("Push buttons, selector switches and other control circuit devices are not energy isolating devices") found in the definition of energy isolating device. The OSHA position expanded the meaning of "other control circuit devices" to include any "control system" regardless of sophistication and effectiveness.In 1989, the OSHA position was to exclude all control systems as a means to control energy. Early electronic control systems were generally not reliable enough to prevent the unexpected energization or release of stored energy unless they were specifically designed for that purpose. Advances in control system technologies in the past 20 years provide an excellent opportunity to improve upon the current requirements in terms of both safety and productivity for machinery, equipment or processes.
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