An electrical area classification (EAC) plan is the documentation used to specify and install appropriately rated electrical equipment in areas at risk of flammable substances igniting from a spark. These requirements allow plants to not only meet Occupational Safety and Health Administration (OSHA) regulations but mitigate the risk of an explosion. These documents, consisting of plot plan drawings, elevation drawings and descriptions of flammable or combustible materials, are key to determining which types of electrical equipment are safe to install and where to install them in a plant.

When engineers specify electrical equipment, or before electrical contractors or construction workers install electrical equipment, EAC plans are consulted so that electrical equipment can be installed with strict adherence to the National Electrical Code (NEC) regarding hazardous locations. The NEC does not make determinations as to what areas should be electrically classified and how, instead deferring to other recommended practices from organizations such as the National Fire Protection Association and American Petroleum Institute to make determinations on EAC boundaries, classification types and temperature codes. For example, any flammable gas that could potentially come into contact with a hot surface must be accounted for to prevent a dangerous incident.

Adherence to the NEC on hazardous locations requires updated EAC plans developed by a team of experienced engineers to make the classifications based on the recommended practice documents. According to OSHA section 29 CFR 1910.307(b), this EAC documentation “shall be available to those authorized to design, install, inspect, maintain, or operate electric equipment at the location.” Documentation of and compliance with electrical area classification practices is federal law.

An accepted industry practice is to review and update EACs every three to five years, or whenever significant changes have been made to processes that could potentially affect the existing EAC. Typical engineering practices should include a complete audit of currently installed electrical equipment to verify the installed equipment adheres to the NEC regarding the EAC. If changes to the NEC or EAC have occurred that make the installed equipment noncompliant, then the equipment should be upgraded or efforts should be made to reduce the EAC to be in compliance with the NEC.

It is not uncommon for audits and reviews of EACs to find outdated classification boundaries against modern recommended practices. These audits also discover changes to EAC boundaries required as a result of updated plant processes and required adjustments to existing electrical equipment installations consequently. When EACs and their boundaries are outdated, or when electrical equipment is no longer suitable for an existing environment, the plant is operating despite the risk of electrically igniting explosive materials in the area. Should an energy release incident occur, discovery periods in the resulting litigation often start with the investigation team examining the status of plant EAC documentation as either a potentially contributing cause of the accident or an indicator of employer negligence with regard to plant safety.

Periodic reviews, updates and audits to facility EACs are frequently overlooked by plant personnel, as the engineering effort required to complete a full review does not yield an obvious return on investment. Costs associated with improper electrical equipment installation that doesn’t meet EAC can be avoided by maintaining proper EAC documentation in the first place. Additionally, avoiding a dangerous situation associated with igniting a flammable or explosive material is priceless for maximum plant safety.


Keeping a facility online directly impacts profitability, so electrical systems play an outsized role in the success of industrial, refinery and petrochemical operations. A turnkey approach to electrical system planning, engineering, procurement, construction and maintenance delivers the reliability, resiliency and availability these systems demand.

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Simon Palacio is a business development manager for Burns & McDonnell in Houston, where he specializes in power systems for industrial and oil and gas clients. He is a licensed professional engineer in 11 states and has worked with many of the largest petrochemical and utility companies in North America.