Does activating an emergency stop button or turning off a machine allow employees to bypass a guard?

No, an emergency stop or “e-stop” button is generally a circuit interruption device, not an energy isolating device. Similarly, turning a power switch to the “off” position is not sufficient. According to OSHA, an “energy isolating device” means something that “physically prevents the transmission or release of energy.” Further, 1910.147 clarifies that “Push buttons, selector switches and other control circuit type devices are not energy isolating devices.”

OSHA also addressed an employer question of whether the “exclusive control” exception for cord and plug equipment could apply to other machines when the power switch was under the control of the employee doing the maintenance. OSHA stated that the cord and plug exception does not apply to on/off switches.

Simply turning off a machine using a power switch or activating an emergency stop button does not allow employees to avoid following lockout/tagout procedures.