---
title: "What Is an Arc Flash Study?"
description: "What an arc flash study calculates, the five stages of the work, the IEEE 1584-2018 method behind the numbers, and the NFPA 70E and OSHA rules that make the results matter."
published: "2026-08-29"
canonical: "https://blog.arcflashflorida.com/blog/what-is-an-arc-flash-study"
author: "Jake Gregory"
---

An arc flash study is an engineering analysis of a facility's electrical distribution system that calculates, for every piece of equipment a worker might open, how much thermal energy an arcing fault would release at working distance (incident energy, measured in calories per square centimeter, or cal/cm²) and how far that hazard reaches (the [arc flash boundary](https://blog.arcflashflorida.com/blog/arc-flash-boundary)). NFPA 70E calls it an arc flash risk assessment. It produces three things you can hold: the warning labels on your equipment doors, the personal protective equipment (PPE) selections those labels drive, and the written record that satisfies an employer's hazard-assessment duty under OSHA.

Picture a maintenance lead in front of a 480-volt motor control center (MCC), the tall metal cabinet full of stacked compartments called starter buckets, each bucket holding the contactor and overload protection for one motor. One bucket has failed, the line is running, and shutting the whole MCC down costs a shift. Without a study, "is this safe to open live" is a guess dressed up as experience. With one, the label on that door states the incident energy at a stated working distance and the arc flash boundary in feet and inches, which decides what the technician wears and whether the job should be done energized at all.

## What does the study calculate?

Two numbers per piece of equipment, plus the conditions behind them. Incident energy is the heat that would land on a worker standing at a defined working distance during an arcing fault, expressed in cal/cm². The arc flash boundary is the approach distance at which that energy has dropped to the burn-onset threshold, so anyone standing inside that line during an arc is in the thermal hazard. Everything else in the report exists to make those two numbers defensible.

![The three outputs an arc flash study produces per equipment: incident energy in cal/cm2, the arc flash boundary, and label plus PPE data](https://yfvhnfihkflbnivhcgge.supabase.co/storage/v1/object/public/blog-images/arc-flash-florida/what-is-an-arc-flash-study/figure-1.svg)

The calculation method comes from IEEE 1584-2018, whose published scope [covers three-phase AC equipment and conductors from 208 V to 15 kV](https://standards.ieee.org/ieee/1584/5802/) and explicitly excludes single-phase AC systems, DC systems, short-circuit and overcurrent-coordination studies, and PPE recommendations.

That exclusion list is worth reading twice, because it describes what buyers actually need. IEEE 1584 tells an engineer how to convert fault current and clearing time into incident energy. It does not tell them your available fault current, judge whether your breakers trip in the right order, or pick your gear. Those are separate scopes of work, and a complete engagement includes them, because the incident-energy number is meaningless without them.

The 2018 method also made the answer sensitive to physical details the older method ignored, including electrode configuration (how the conductors are arranged, and which direction the arc blows) and enclosure size. Two panels with identical fault current and identical clearing time can carry different labels because one is a shallow surface-mounted box and the other is a deep switchgear cubicle.

## What are the five stages of the work?

The work runs in a fixed order because each stage feeds the next. Stage one is the only one that happens in your building; the rest happen inside the model built from it. Shortcut stage one and the report comes back with numbers nobody trusts.

| Stage | What happens | What it produces |
|---|---|---|
| 1. Field data collection | A walk-down from the utility service to the last panelboard: nameplates, conductor sizes and lengths, breaker and fuse types, relay settings, transformer impedance | An accurate model of what is installed today, plus a one-line diagram (the single-page map of how power flows through the building) if none exists |
| 2. Short-circuit analysis | Computes maximum and minimum available fault current at every bus (the common set of conductors inside a piece of gear that everything downstream connects to) | The fault current every later stage depends on |
| 3. Protective device coordination | Models how fast each breaker, fuse, and relay clears a fault, and whether the closest device opens first (selectivity) | Clearing times, and a list of settings worth changing |
| 4. Incident energy analysis | Applies IEEE 1584-2018 at each bus using fault current, clearing time, working distance, electrode configuration, and enclosure geometry | Incident energy in cal/cm² and an arc flash boundary per location |
| 5. Labeling and reporting | Labels printed and applied per NFPA 70E 130.5(H), with the calculations, the one-line, and the assessment record delivered together | Field-ready labels and the documentation an inspector or an insurer asks to see |

The min/max pair in stage two is the part most people read past, and it often decides the answer. Maximum fault current is the obvious hazard. Minimum fault current is frequently the worse one, because a lower arcing current can sit just under a breaker's instantaneous trip threshold and burn for a full second instead of clearing in a few cycles. Longer burn, more energy delivered, higher number on the label. That is why the worst incident energy on a site is not reliably at the highest voltage. OSHA makes the same point from the injury side: it describes an electric arc as [a type of electrical explosion that can exceed 35,000°F](https://www.osha.gov/electrical/flash-hazards), and notes that most arc flash burns come from the arc igniting the worker's clothing rather than from the arc itself.

## Does it matter which edition the study was built on?

Yes. IEEE 1584-2018 replaced the 2002 edition, and the two methods do not produce the same incident energy for the same equipment. Jim Phillips, P.E., Vice-Chair of the IEEE 1584 Arc Flash Working Group and a Technical Committee member on NFPA 70E, [draws the line precisely](https://www.powerandcables.com/ieee-1584/): "The overall risk assessment process is the same as before. i.e. Arc rated clothing and PPE are selected with an arc rating sufficient for the calculated incident energy."

What changed sits underneath that process. "However, the difference is with the incident energy calculations using IEEE 1584," Phillips says. "The calculations and modeling have changed dramatically." A report built on 2002 math and one built on 2018 math are not interchangeable documents, even when the equipment has not moved an inch.

NFPA 70E's next edition, the 14th, is in revision now, with issuance expected in late 2026 into 2027. OSHA measures a facility against current recognized practice, not against whichever edition your last report cited, so the edition printed on the cover is worth checking before somebody else checks it.

## What makes it required?

NFPA 70E Section 130.5 requires an employer to perform an arc flash risk assessment before work is done on energized equipment that has not been put into an electrically safe work condition. The assessment identifies the hazard, estimates the likelihood of an incident, determines the potential severity of injury, and then drives protection by one of two methods: the [incident energy analysis method](https://blog.arcflashflorida.com/blog/incident-energy-analysis-method) in 130.5(G) or the PPE category method in 130.7(C)(15), never both on the same equipment. 130.5(H) sets what the resulting label must show.

[NFPA 70E](https://www.nfpa.org/product/nfpa-70e-standard-for-electrical-safety-in-the-workplace/p0070ecode) is a voluntary consensus standard, not a federal regulation. OSHA has said in [standard interpretations](https://www.osha.gov/laws-regs/standardinterpretations/2003-07-25) that it has not conducted rulemaking to adopt 70E's specific requirements, and that it has [no arc-flash label rule of its own](https://www.osha.gov/laws-regs/standardinterpretations/2006-11-14). None of that makes the exposure theoretical. OSHA treats an industry consensus standard as evidence that a hazard is recognized and correctable under the General Duty Clause, and it separately enforces [29 CFR 1910.132(d)](https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.132), which requires an employer to assess the workplace for hazards, select PPE that protects against what the assessment found, and certify that assessment in writing.

Which events oblige you to commission a study, and how long a finished one stays current, are separate questions with their own answers. This page is the definition.

## What does stage one turn up in a coastal plant?

Field data collection is where Florida conditions land in the model. Storm work leaves a trail: switchgear replaced after a hurricane, a utility service upgraded to a larger transformer, a permanent generator and transfer switch added after a week of running on rentals. Each of those changes available fault current, and none of them update the label on the door by itself.

Condition matters as much as configuration on the coast. A fault does its damage in a few cycles; corrosion does comparable damage to a bolted joint over years, pitting and loosening terminations until contact resistance climbs. At a barrier-island wastewater plant on the Atlantic side, the ingredients arrive together: salt air, hydrogen sulfide off the headworks, and gear that cannot be shut down because the lift stations keep pumping through the afternoon storms. A walk-down there means opening cabinets nobody has opened in years, and the model has to reflect what is inside them now, not what a drawing from the 1990s claims.

That is the part a facility can plan around. Arc Flash Florida handles the whole job in one engagement, including building a one-line diagram for sites that no longer have a current one, and the field walk-down is scheduled to fit your production schedule rather than interrupt it.

The end state is the same in every building: a current label on every piece of gear, calculations on file behind it, and nobody standing in front of a closed door guessing.