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NFPA 70E and Arc-Flash Calculations Above 15 kV
February 3, 2026
- Arc Flash & Electrical Power Training by Jim Phillips
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Most arc-flash labels as required by NFPA 70E appear with the word “WARNING” on an orange background. However, I occasionally see red labels and even green labels.
So… what color is correct?
The technically correct answer is: it depends.
To understand why, we need to separate what NFPA 70E requires, what ANSI standards define, and what has become common industry practice.
NFPA 70E requires that electrical equipment likely to require examination, adjustment, servicing, or maintenance while energized be field marked with an arc-flash label. The label must include specific information such as:
However, NFPA 70E does not specify label colors or signal words. That part is left to other standards—primarily ANSI Z535.
The ANSI Z535 series defines safety signs and tags used to warn people of personal injury hazards. It defines signal words, each associated with a specific color, based on the severity of the hazard if it is not avoided.
Yellow / CAUTION
Orange / WARNING
Red / DANGER
From a purely technical standpoint, arc-flash hazards can be fatal, which raises the obvious question:
Shouldn’t arc-flash labels be red?
Despite the severity of arc-flash hazards, industry practice has informally standardized on orange “WARNING” labels for most arc-flash applications.
Why?
As a result, orange WARNING labels strike a balance; they communicate serious risk without overstating severity. Red/DANGER labels are normally used for extreme incident energy levels, but there is no consensus threshold defined in NFPA 70E or ANSI.
Red/DANGER labels are not prohibited, but they should be used carefully and consistently.
Using red for normal arc-flash hazards can:
If red labels are used, it should be part of a clearly documented labeling philosophy, ideally referenced in the arc-flash study or electrical safety program.
Historically, Red/DANGER labels were used when the calculated incident energy exceeded 40 cal/cm2 due to an informational note from NFPA 70E stating: “When incident energy exceeds 40 cal/cm2 at the working distance, greater emphasis may be necessary with respect to de-energizing when exposed to electrical hazards.”
The 2018 Edition of NFPA 70E deleted this note since the emphasis should always be to de-energize not just above 40 cal/cm2.
And Green Labels? 🚨
This is where things go off the rails.
Green is not an ANSI Z535 hazard color.
Some arc-flash software packages allow custom color schemes, and I have seen green labels occasionally appear when:
The problem?
A green label can easily be interpreted as “safe”—and electrical equipment is never hazard-free.
Even when incident energy is low:
Using green for arc-flash labels can create a false sense of security and is not aligned with ANSI Z535 intent.
To stay aligned with NFPA 70E, ANSI Z535, and accepted industry practice:
Consistency and clarity matter just as much as technical accuracy.
With a career beginning in 1981 and Brainfiller launching in 1987, Jim has built a global reputation as a trusted leader in electrical safety.
He currently:
💡 Did you know? Many NFPA 70E trainers learn the material by attending Jim’s classes—while Jim is involved directly with the standards they teach.
All training is available live, on-site, or on-demand, and includes completion certificates with CEU/PDH documentation.NFPA 70E Qualified Worker Training (8 hours)
Covers risk assessment, PPE, LOTO, establishing an electrically safe work condition, and auditing requirements.How to Perform an Arc-Flash Study | IEEE 1584 (16 hours)
Modeling, arcing current, incident energy, arc-flash boundaries, and system-level mitigation.Fundamentals of Electrical Safety (2 hours)
Shock hazards, arc-flash basics, and the building blocks behind NFPA 70E.DC Electrical Safety Fundamentals (2 hours)
Key safety practices for data centers and DC systems.
Because Jim is embedded in NFPA, IEEE, IEC, and NEC committees, he sees emerging trends before they appear in the codebook.
His training materials are updated immediately after each standards cycle, keeping teams aligned with NFPA 70E, IEEE 1584, and OSHA expectations.
🔧 From code to craft: Jim explains why requirements exist and how to apply them correctly in real electrical systems.
Partnering with Jim Phillips ensures your team learns NFPA 70E and arc-flash safety from someone who has helped guide the direction of the standard—not from copied material.
