emergency power off (EPO) button

What is an emergency power off (EPO) button?

The emergency power off button, also called an EPO switch or EPO panel, is a safety measure for quickly disconnecting electrical power to a particular piece of equipment or facility in the event of an emergency. The button safely shuts down all power, including uninterruptable power supplies, batteries and generators from a central location.

EPO buttons can be found in places such as manufacturing plants, telecommunications facilities and IT data centers. The goal of shutting down power in a centralized manner is to limit damage in the event of a disaster and make it safer for rescue personnel to deal with the emergency. They should be used in cases where there is the potential for loss of life or major property damage, such as fires, evacuations, floods, or electrocution.

Data center teams who do install an EPO button should clearly mark the button's presence and install it under a clear, lift-cover box, preferably with an integrated alarm, to avoid the risk of somebody hitting it accidentally and causing unintentional downtime. This has historically been a major cause of data center outages, usually when the button was mistaken for a door release. An accidental use of the EPO could result in a major loss of revenue or even extended downtime as the computers are not properly shutdown prior to power off.

If someone tells you not to push the big red button, don't push it.

The specific requirements around an EPO button's size, placement and accessibility vary and depend on local jurisdiction. Historically, EPO buttons had to be installed at every exit door. However, since the 2011 version of the National Electrical Code (NEC), it is possible to put a single EPO switch in a nearby room with approval of the code inspector and the fire marshal.

EPO buttons may also be linked together and controlled centrally. They may be attached to a fire panel or building control system. These systems may automatically employ the EPO before fire sprinklers are activated to avoid the risk of electric shock.

EPO button vendors include APC by Schneider Electric and Safety Technical International.

Example of an emergency power off (EPO) button.
Emergency power off buttons safely shut down all power to a piece of equipment or facility.

Electronic Power Off button history

The history of the EPO button dates to a 1959 fire at The Pentagon that caused over $6 million in damages. Three years later the National Fire Protection Association released its first Standard for the Protection of Electronic Computer Systems, which became known as NFPA 75. While NFPA 75 is technically a recommended standard, it is not required by law unless adopted by the local jurisdiction. Even then, it may be negotiable with the authority-having jurisdiction.

In contrast, NFPA 70, more commonly known as NEC, is a mandatory code. Although Article 645 defines the circumstances under which an EPO button is required, the definition is often misinterpreted. In most jurisdictions, the EPO switch is not automatically mandated in data centers unless the owners and designers want to take advantage of certain options such as loose power whips under air plenum floors or non-plenum cable.

Data centers contain risks such as height, environmental and electrical hazards. Keep your staff safe by assessing the level of risk and creating a comprehensive safety plan based on these best practices.

This was last updated in April 2024

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