Under the cover is a battery-operated micro-switch that sounds an audible 90-decibel (piercingly loud) alarm, while instantly alerting security through a second micro-switch that the cover has been lifted. A phone is a few feet away from the EPO switch.
Additional EPO requirements include having a system that can be serviced and maintained fail-safe. That means it can be maintained while critical load is being powered. Many clients are terrified of changing a burned-out light bulb on their EPOs for fear of accidentally shutting down their datacentres.
Some other designs we have developed require the closure of two latching push buttons that need a key to release. Others have the alarm switch in the EPO cover simultaneously cause a video camera to rotate and film the EPO because disgruntled employees have perpetrated some malicious EPO activations.
As a final consideration, the label can be expanded to read "EPO (emergency power off) button. This will shut down all equipment in this room. Use for life saving emergency only." It may be a good idea to have the sign in an alternative language that is used by non-English-speaking occupants.
More than 30 years ago, code officials determined the need for EPOs because power installed under a raised floor could start a concealed fire. Also, since there are so many circuit breakers in a datacentre, it is difficult to determine a source for disconnecting if someone is being electrocuted. Modern components that mitigate the need for EPO include fire-/smoke-detection systems under the raised floor and "ground fault (GFI)" settings in circuit breakers.
Actual cases where EPO activation has saved lives are non-existent. The Canadians are intentionally attempting to remove this requirement from their codes. Unfortunately, not unlike many examples in building codes, once approved, they are very difficult to exorcise from the code books.
Edward C. Koplin, professional engineer and certified energy manager, is a principal of consultancy X-nth. He has been an advisor to the Site Uptime Institute and has evaluated, designed and commissioned over 3 million square feet of Fortune 500 datacentres. He can be reached at email@example.com.