Here’s the long and short of it. Working on “live” electrical equipment in data centers exposes workers to potential death or disabling injury from arc flash, arc blast, or electric shock. In fact, electrical injuries cause “nearly one fatality every day!”1  And OSHA takes this all very seriously. It cited The Hartford Financial Services Group Inc. and Grubb & Ellis Management Services Inc. with serious violations of workplace safety standards for exposing workers to electrical hazards at The Hartford's corporate headquarters and data center in Hartford.

OSHA found that The Hartford's data center policy required electricians employed by its maintenance contractor, Grubb & Ellis, to perform work in live electrical panels for computer equipment without first de-energizing the panels as required under the agency's standards. Grubb & Ellis, for its part, failed to de-energize the electrical panels before having its employees perform installation work and grid upgrades on them.2 Fortunately, no workers were injured. The companies were fined.

Data center operators have performed electrical maintenance and branch circuit installations “live” because, historically, they believed that data center mission critical operations were exempt — operating 24/7/365. According to the Uptime Institute, “about one-third of [data center] organizations allow maintenance activities on energized electrical equipment at voltage levels that could cause health or human-safety consequences.3 

But the status quo is changing, brought on by recent data center electrical accidents, an increased enforcement posture by government agencies, a better understanding in the workplace of electrical hazards, as well as the rules and regulations, data center infrastructure design improvements, and an overall culture shift in the data center industry that now emphasizes safer working conditions for data center engineers and electrical contractors.


OSHA regulations are considered the “why.” However, when determining and applying the electrical rules, regulations, and safety practices in data center operations, NFPA  70E “Standard for Electrical Safety in the Workplace” is the “how.” While OSHA and NFPA 70E use different language, the NFPA 70E consensus standard does not require anything, for all intents and purposes, which is not already in the OSHA regulations.

You’ll find OSHA’s electrical safety standards at 29 CFR Part 1910, Subpart S. OSHA requires [29 CFR 1910.333(a)(1)] that “live” electrical parts operating at 50 volts or more must be de-energized prior to the commencement of work unless the employer can demonstrate that de-energizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. These exceptions include:

  1. Testing of equipment that can only be performed energized
  2. Working on equipment that is part of a continuous industrial process
  3. Working on equipment supporting life safety and/or illumination for an area
  4. Working where de-energizing presents an increased hazard


Testing of Equipment

Most electrical equipment requires regular inspection and testing by a competent professional to identify damage to the equipment or a possible reduction in its expected life span from prevailing conditions.

In the past — according to sections 90 and 91 of the American Electricians’ Handbook, 1942 — electricians often tested “circuits for the presence of voltage by touching the conductors with the fingers. This method is safe where the voltage does not exceed 250 and is often very convenient for locating a blown-out fuse or for ascertaining whether or not a circuit is alive…The presence of low voltages can be determined by  ‘tasting’.4 Three quarters of a century later, electricians are still testing circuits “live.”

Fortunately today, they follow and use advanced electrical safety practices and tools. They rely on improved techniques that reduce the risk of electrical shock and arc flash. These techniques comply with OSHA regulations that specifically exempt “testing of electric circuits that can only be performed with the circuit energized” [Note 2 in 29 CFR 1910.333(a)(1)]. Under this testing of equipment exception, “live” testing such as troubleshooting or diagnostics, thermal scanning, testing to verify de-energization, and meter readings can be performed energized in order to obtain meaningful test data, results, and information.

There is one other electrical work condition falling within testing of equipment that should be mentioned, the minor servicing exemption. Minor tool changes/adjustments/calibrations, and other minor servicing activities during “normal production operations” are permitted if they are routine, repetitive, and integral to the use of the equipment for production. This is in the note contained in 29 CFR 1910.147(a)(2)(ii)(B). Data center operators are often unaware of this minor servicing exemption. With the right set of electrical safety processes and procedures in place, an employer can demonstrate applicability and use this exemption appropriately in limited situations.

Continuous Industrial Process

Data center operators have long argued that energized electrical work for electrical maintenance and “live” branch circuit installations is allowable because the nature of 24/7/365 data center operations meets the continuous industrial process exception.

Unfortunately, this argument falls flat. As far as OSHA is concerned, de-energization of a panel does not introduce additional or increased hazards. It’s just an inconvenience and it is feasible. The term “continuous industrial process” came from the NEC where it’s used in situations where the orderly shutdown of integrated equipment and processes would introduce additional or increased hazards.

To qualify for the exception found in Note 2 of 29 CFR 1910.333(a)(1), the data center operator must determine if the orderly shutdown of the related equipment and processes would introduce additional or increased hazards. If so, the work may be performed “live” using the electrical safe work practices found in 29 CFR 1910.331-1910.335. These practices include, but are not limited to, using insulated tools, shields, barriers, and personal protective equipment.

Conversely, if the orderly shutdown of the related equipment and processes would not introduce additional or increased hazards, but simply alters or interrupts data center operations, then de-energization of the equipment would be feasible, and the continuous industrial process exception would not apply. The burden of proof, whether or not an exception applies, falls to the data center operator. Failing to comply with these rules and regulations is a violation of applicable law, rules and regulations, which could be punishable by fine and/or imprisonment.

Supporting Life Safety and/or Illumination for an Area and De-energizing Introduces Increased or Additional Hazard

Neither inconvenience, financial considerations, nor scheduling challenges constitute a legitimate reason to perform energized electrical work. So, besides the testing of equipment exception, is there ever a situation or condition where “live” work must be performed in a data center? In general, no. However, there are situations and conditions where de-energizing “introduces increased or additional hazards” and the exception indicated in Note 1 in 29 CFR 1910.333(a)(1) may apply. These situations include interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.

For example, some data center operators provide services to city and county government agencies, which are responsible for emergency response actions in the communities they serve — 911 calls, fire department response, etc. You could argue that de-energization “introduces additional or increased hazards” to the community if a government server lacking redundancy and dedicated for emergency response was de-energized for electrical maintenance or circuit installation. However, it appears that this supporting life safety and/or illumination for an area exception in this context has never been tested in an OSHA proceeding or legal context, nor is there an OSHA interpretation letter to reference as guidance.


As mentioned, the testing of equipment exception is limited, but clear and reasonable while the continuous industrial process exception argument appears to fail. There are only special circumstances where the supporting life safety and/or illumination for an area exception can be applied to data center operations. These exceptions and conditions are not new requirements. All employers, including data center operators who allow workers or contractors to work on or near energized electrical equipment and circuits, must comply with all OSHA electrical rules and regulations.6 The odds of a serious accident are stacked against data center operators who allow improper energized electrical work in their data centers.

To make things even more complex, many electrical contractors and maintenance vendors now refuse to allow their electricians to conduct work “live” in data centers. The most qualified electrical contractors and maintenance vendors leave the dangerous and potentially non-compliant work to the “not so” qualified electrical contractors, increasing the operational and safety risk for data center operators and their customers. These conditions create significant business challenges for data center operators who promote 100% uptime to their customers. Fortunately, there are solutions.

Data center operators need to implement an energized electrical work strategy that includes many different types of components. For example, effective electrical work, advanced scheduling and coordination is a must, and supports a strong stakeholder partnership. By planning around the customer’s business hours and priorities, electrical work becomes easier to implement and solves many of the issues with de-energization.

Another key component is ensuring that the redundancy required to meet the letter of the electrical safety rules and regulations is initially disclosed and offered to customers so that the deployment allows maintenance and branch circuit installation to occur de-energized without business interruption. Finally, use of best-in-class electrical safety practices that reduce the risk of electrical hazards in data centers is vital. Data center operators now invest in new technologies to help manage this risk, including but not limited to:

  • Finger safe panel boards — these systems utilize circuit breakers with long insulated connectors on the line side to reduce exposure

  • Overhead busways — these systems utilize pre-installed busways and prefabricated junction boxes that connect to the bus.

By utilizing finger-safe products and non-conductive covers or barriers, data center operators help prevent personnel exposure to “live” parts. Workers maintain systems without the risk of electrocution and without the need to de-energize large portions of the data center.7


If data center operators can’t justify “live” work, electrical equipment must be de-energized before anyone works on it. OSHA identifies only two justifiable reasons for working “live”:

  • It is infeasible to de-energize as in the case of testing, troubleshooting, or in some supporting life safety and/or illumination for an area situations

  • De-energizing introduces additional or increased hazards

As the data center industry enters a new era of electrical safety compliance, it’s imperative that data center operators follow the applicable regulations and consider the various options available to them. Leading data center operators are getting ahead of the curve and implementing proactive energized electrical work policies and practices. This ensures that their customers are provided as close to 100% uptime as possible while protecting their engineers and the electrical contractors they hire.

This article is not intended to be used as legal advice. If you need legal advice, please contact an attorney directly.

  1. Cawley, James and Homce, Gerald. “Occupational electrical injuries in the United States, 1992–1998, and recommendations for safety research,” National Institute for Occupational Safety and Health, 2003.
  2. OSHA Regional News Release, US Department of Labor. Office of Public Affairs, June 1, 2011.
  3. Stansberry, Matt. “Uptime Institute Data Center Industry Survey 2015.” Uptime Institute, 2015.
  4. Croft, Terrell. American Electricians’ Handbook. McGraw-Hill Book Company, 5th Edition, page 38, 1942
  5. OSHA Interpretation Letter, US Department of Labor, Directorate of Enforcement Programs, December 19, 2006
  6. “OSHA Cites Pure Power Technologies After Worker Burned by Electrical Arc Flash at Waukesha Foundry.” Electrical Construction and Maintenance, January 15, 2014.
  7. Leclerc, Walter. “Data Center EHS 101.” Occupational Health & Safety, April 2016.