What To Do When You See a New Arc Flash Label

Jeff Kershner
Jul 21
4 min read

Everyday scenarios—and how to stay safe when the stakes are high

Imagine this: you’ve operated the same equipment safely for 20 years. Then one day, an arc flash label appears on it. Suddenly, you’re being told that what used to be “normal” might now require special PPE—or even be too dangerous to handle.

That confusion is common. At Guidant, we regularly hear questions like:

“Do I really need to suit up just to flip a breaker?”
“What does this ‘incident energy’ number on the label mean for me?”
“If this says 42 cal/cm², can I even work on it?”

This article walks you through real-life examples and provides practical guidance, based on NFPA 70E^® and field-tested best practices, to help you stay safe and confident around labeled equipment.

Scenario 1: “Do I need to suit up just to switch a breaker?”

Let’s say your equipment now has a label reading 6.1 cal/cm². You’ve turned this breaker on and off for years without issue. Now you're wondering: do I need to gear up just to flip a switch?

The short answer: Maybe.

It depends on whether the equipment qualifies as being under “normal operating conditions.”

According to NFPA 70E^® 2024 Table 130.5(C), you must evaluate the likelihood of an arc flash for your specific task. For example:

Operating a circuit breaker or switch:

If the equipment is in normal operating condition → No likelihood of arc flash
If it’s abnormal (e.g., recently tripped, damaged, or poorly maintained) → Arc flash is likely

What counts as “normal”?

Per NFPA 70E^® 2024 – 110.2(B) Exception No. 1, all of the following must be true:

Properly installed
Properly maintained
Rated for the available fault current
Used per manufacturer’s instructions
The equipment doors are closed and secured
All equipment covers are in place and secured
No visible damage or signs of failure

If even one of these conditions isn’t met, the task no longer qualifies as “normal,” and PPE is required.

⚠️ Example: If a breaker tripped and you’re resetting it—that’s not normal operation. The risk is elevated, and arc-rated PPE must be worn.

Scenario 2: What Does This “Incident Energy” Number on the Arc Flash Label Mean for Me?

The incident energy value on your arc flash label—say, 6.1 cal/cm²—tells you how much thermal energy you could be exposed to during an arc flash at working distance. It directly determines what PPE you need to wear to stay protected.

If the label says 6.1 cal/cm², you must wear arc-rated clothing and gear rated to at least that level (when there is an increased likelihood of an arc flash occurring) —including shirt, pants, face shield or hood, gloves, and more. The label also shows the arc flash boundary, the distance unprotected workers must stay back.

This number isn't theoretical. It’s based on calculations from a hazard assessment and reflects real risk, even for tasks that may feel routine. Whether you’re switching a breaker or troubleshooting, make sure your PPE matches or exceeds the label's rating.

Want to understand each part of the label and how to apply it in real situations? Check out our article about arc flash labels for a detailed breakdown.

Scenario 3: “The label says 42 cal/cm². Can I still work on it?”

Labels like this can be intimidating. Workers often wonder if there's a “cutoff” value that makes a task illegal or impossible to perform.

The answer: Yes, you can work on high incident energy equipment—if you meet the requirements.

You must:

Be a qualified electrical worker
Wear PPE rated for the incident energy (e.g., >8 cal/cm² is common; if the label indicates 42 cal/cm², then you need a suit on that is a higher rating than that… they are available)
Complete a task-specific risk assessment

Some companies set internal policies to prohibit work above 40 cal/cm². This is not a regulatory limit. It’s a safety-based decision, often made to reduce exposure for employees and shift that risk to specially trained contractors.

Why 40 cal/cm²?

That number originated in the NFPA 70E^® PPE Category Method, which caps out at Category 4 PPE (≥40 cal/cm²). However, if you're using the Incident Energy Method, there is no upper limit—as long as your PPE matches the hazard level.

How Do I Know What PPE to Wear?

There are two accepted methods for determining the right PPE:

Incident Energy Calculation Method (Recommended)

Starts with a comprehensive arc flash analysis
Calculates exact incident energy at the work location using engineering software (e.g., EasyPower, SKM)
PPE is selected based on NFPA 70E^® Table 130.5(G)
No upper limit: you match the PPE to the actual energy

Category Method (Table Method)

Based on NFPA 70E^® Table 130.7(C)(15)(a)
Uses system values (voltage, fault current, clearing time)
Only valid if all conditions are met
Caps out at Category 4 (≥40 cal/cm²)

Common Pitfall:

You cannot safely use the table method unless you have confirmed system data. If the fault current or clearing time are unknown, the method cannot be used reliably.

Takeaway: Don’t Rely on Assumptions—Rely on Training and Risk Assessment

Whether it’s a new label on familiar gear or a warning sign on a high-risk panel, your best defense is knowing how to interpret the hazard and understanding what actions are required.

Key steps:

Check the task’s likelihood of arc flash using Table 130.5(C)
Determine if the equipment qualifies as “normal operation”
Use either incident energy analysis or PPE categories correctly
Always follow your facility’s safety policies—especially if they go beyond minimum standards.

If your crew needs help interpreting labels or building safer procedures, reach out to our team. At Guidant Power, we help make electrical safety understandable, actionable, and compliant—so your team can focus on doing the job safely.