An arc flash study report tells you how much energy could be released at each point in your electrical system during a fault, what protective equipment workers need, and where your highest-risk areas are. The problem is that most of these reports are written by engineers for engineers. If you’re a facility manager or safety director who just received a 50-page document full of numbers, diagrams, and technical language, this guide will help you understand the sections that matter most and turn the data into action.
Why the Report Matters More Than the Study
Getting the arc flash study done checks a compliance box. But the report is where the operational decisions live. It drives your PPE program, your equipment labeling, your safe work procedures, and your capital planning for electrical system upgrades.
A report that sits in a drawer doesn’t protect anyone. Understanding it does.
Start With the One-Line Diagram
Most arc flash study reports open with an updated one-line diagram (also called a single-line diagram). This is a simplified schematic showing how power flows through your facility, from the utility service entrance through transformers, switchgear, panels, and downstream equipment.
Think of it as a map. Every bus, breaker, fuse, and panel appears on it. Each of those locations has been analyzed, and the results throughout the rest of the report tie back to specific points on this diagram.
Before you read anything else, compare the one-line diagram to what actually exists in your facility today. If panels have been added, loads have changed, or equipment has been swapped since the field data was collected, those discrepancies affect the accuracy of every calculation downstream. Flag anything that doesn’t match and discuss it with the engineering firm that produced the report.
Incident Energy: The Number That Drives Everything
This is the core data point in the report. Arc flash incident energy is the amount of thermal energy (measured in calories per square centimeter, or cal/cm²) that would reach a worker standing at a defined distance from the arc source during a fault event.
Here’s how to interpret the numbers you’ll see:
1.2 cal/cm² is the threshold for a second-degree burn on unprotected skin. Any equipment with incident energy at or above this value requires PPE.
Values between 1.2 and 12 cal/cm² generally correspond to PPE Category 1 or 2. These are your everyday arc-rated shirt, pants, face shield, and hearing protection situations.
Values between 12 and 40 cal/cm² move into PPE Category 3 or 4 territory. Full arc flash suits, hoods, and multi-layer arc-rated clothing. These are the locations where work takes significantly longer due to PPE burden, and where you should be asking whether the task can be performed de-energized instead.
Values above 40 cal/cm² exceed the maximum PPE rating defined by NFPA 70E. At these locations, energized work should not be performed. The report’s corrective action recommendations for these points deserve your immediate attention.
Scan the report for the highest incident energy values first. Those locations are your top priorities for both PPE compliance and engineering remediation.
Working Distance and Arc Flash Boundary
Every incident energy calculation in the report assumes a specific working distance between the worker and the arc source. This varies by equipment type. Panelboards typically use 18 inches. Switchgear and motor control centers may use 24 or 36 inches.
The report also defines the arc flash boundary for each location. This is the distance at which incident energy drops to 1.2 cal/cm². Anyone crossing inside that boundary during a fault would receive a burn-level exposure.
As a facility manager, the arc flash boundary tells you two things: where to post restricted access signage and where PPE enforcement begins. If workers routinely enter the arc flash boundary during operations or maintenance, they must be qualified, trained, and wearing the correct gear. No exceptions.
What Goes on the Labels
NFPA 70E requires arc flash labels on equipment where workers may interact with energized parts. Your report should provide the label data for every studied location. At minimum, each label includes the incident energy at working distance, the arc flash boundary, the required PPE, the nominal system voltage, and the date the study was performed.
Some reports also include the available fault current and the protective device clearing time. That additional information is useful context when your system changes later, because it lets a qualified engineer quickly assess whether a modification might have altered the incident energy at that location.
Action item: Walk your facility and compare the labels on your equipment to the data in the new report. If labels are missing, faded, or based on an outdated study, replacing them is the single fastest safety improvement you can make after receiving a new report.
The Corrective Actions Section Is Your Capital Planning Tool
The back section of most arc flash study reports includes recommendations for reducing incident energy or improving safety at specific locations. This is where the report transitions from diagnostic to prescriptive, and it’s where many facility managers find the most practical value.
Common recommendations include adjusting protective device trip settings to clear faults faster (faster clearing = lower incident energy), replacing older breakers or fuses with faster-acting equipment, installing remote racking or remote switching capability at high-energy switchgear locations, adding or upgrading zone-selective interlocking to reduce clearing times, and re-evaluating maintenance practices to reduce the frequency of energized work.
Not every recommendation needs to happen immediately. The report’s incident energy values help you prioritize. Locations above 40 cal/cm² where workers currently perform energized tasks are urgent. Locations in the 8-12 cal/cm² range with room for improvement are important but can be phased into your maintenance budget.
Think of the corrective actions list as a capital planning tool. Present it to leadership with cost estimates and a timeline. The report gives you the engineering justification for every dollar you request.
What Triggers a New Report
NFPA 70E recommends reviewing your arc flash risk assessment whenever a major modification is made to the electrical distribution system, or at intervals not exceeding five years, whichever comes first.
Changes that should trigger a re-evaluation include adding or removing significant electrical loads, replacing switchgear, transformers, or large breakers, modifying protective device settings, upgrading your utility service or adding on-site generation, and installing new distribution panels or motor control centers.
If you’re not sure whether your current report still reflects reality, go back to the one-line diagram. If the diagram doesn’t match your facility’s current configuration, the calculations built on that diagram may no longer be accurate.
About Shaw Consulting Services
Shaw Consulting Services LLC is an Atlanta-based electrical engineering firm that specializes in arc flash assessments, power system studies, and electrical safety programs for commercial and industrial facilities. Shaw delivers reports that are technically rigorous and written so facility managers can actually use them, not just file them. If you’ve received an arc flash study report and need help interpreting the findings, or if your facility is due for a new assessment, Shaw’s team is ready to help. Contact Shaw Consulting to schedule your arc flash assessment.
Frequently Asked Questions
What is arc flash incident energy?
It’s the thermal energy (measured in cal/cm²) a worker would be exposed to at a specific distance during an arc flash event. This number determines the PPE requirements for each piece of electrical equipment in your facility.
I received my report but don’t understand the recommendations. What should I do?
Ask the engineering firm that produced it to walk you through the findings. A good firm will schedule a review meeting to explain the high-risk locations, prioritize corrective actions, and help you build an implementation plan. If your current provider won’t do that, it’s worth getting a second opinion.
Can I reduce arc flash incident energy without replacing equipment?
Often, yes. Adjusting protective device trip settings to clear faults faster is one of the most common and cost-effective ways to lower incident energy. Your report’s corrective actions section should identify where this is possible.
What happens if my arc flash labels are outdated?
Workers relying on inaccurate labels may select insufficient PPE. Outdated labels also create compliance exposure under NFPA 70E and OSHA. Updating labels after receiving a new report is one of the most immediate and impactful steps you can take.
How long does an arc flash study take?
It depends on facility size and complexity. A small facility with a few panels might take a couple of weeks. A large industrial campus with multiple buildings and voltage levels could take several months from data collection through final report delivery.