Arc flash labels are everywhere in industrial and commercial facilities. But walk through most plants and you will find labels that are incomplete, outdated, or so generic they are effectively useless. Getting arc flash labeling right is not a cosmetic compliance exercise — it is the critical last step that puts the results of your arc flash study in front of the worker who needs it, at the exact moment they need it.
What NFPA 70E Requires on Arc Flash Labels
NFPA 70E Article 130.5(H) specifies the minimum information that must appear on arc flash hazard warning labels for equipment that may be serviced while energised. The required elements are:
- Nominal system voltage
- Arc flash boundary (expressed in feet and inches)
- Either: the calculated incident energy (in cal/cm²) and working distance OR a PPE category from Table 130.7(C)(15)(c)
- Minimum arc-rated PPE required for work within the arc flash boundary
- For the Incident Energy Analysis Method: date of the study
Labels that show only a PPE category number or a generic ‘DANGER: Arc Flash Hazard’ warning without these specific values are not compliant — and they do not give workers the information they need to make correct PPE decisions.
Common Labeling Failures
In practice, the most common labeling deficiencies Bowtie engineers encounter include:
- Labels that show PPE category without the corresponding arc flash boundary distance
- Incident energy values listed without the working distance they were calculated at
- Labels with no date — making it impossible to determine whether the study is current
- Generic labels applied across all panels in a facility regardless of actual incident energy differences
- Faded, damaged, or illegible labels that have not been replaced after maintenance or painting
- Labels that reference PPE categories that no longer correspond to the calculated values in the updated study
The Working Distance Problem
One of the most consistently misunderstood elements is working distance. Incident energy is only valid at the distance at which it was calculated. A label showing 8 cal/cm² assumes a specific working distance — typically 18 inches for low-voltage equipment. If a worker is working closer than that distance, the actual incident energy they face is higher than the label indicates. Labels must clearly state the working distance so workers can make appropriate adjustments.
When Must Labels Be Updated?
Labels must be updated whenever the arc flash study is updated — which is required every five years or after any major system modification. In practice, this means having a process to ensure that study updates automatically trigger label replacement across all affected equipment. Stale labels from a previous study are not compliant, even if the study itself was once valid.
Bowtie Engineering’s Incident Energy Studies include compliant arc flash labeling as a standard deliverable. Contact our team if your labels are out of date or your study needs a review.
Frequently Asked Questions
What information is required on an arc flash label per NFPA 70E?
NFPA 70E Article 130.5(H) requires arc flash labels to include the nominal system voltage, arc flash boundary distance, either the calculated incident energy with working distance or a PPE category, the minimum arc-rated PPE required, and — for incident energy analysis — the date of the study.
How often do arc flash labels need to be updated?
Arc flash labels must be updated whenever the underlying arc flash study is updated. NFPA 70E requires studies to be reviewed every five years or after any major electrical system modification. Labels from a superseded study are not considered compliant, even if the original study was valid at the time.
Can I use a generic arc flash label across all panels in my facility?
No. Generic labels that do not reflect the actual incident energy and arc flash boundary for each specific piece of equipment are not compliant with NFPA 70E and can put workers at serious risk. Each label should reflect the calculated values for that individual panel or equipment.
What is working distance on an arc flash label and why does it matter?
Working distance is the distance at which incident energy was calculated — typically 18 inches for low-voltage equipment. The incident energy value on a label is only valid at that distance. If a worker is closer, the actual energy exposure is higher. The working distance must appear on the label so workers can assess whether additional PPE precautions are needed.
Does an arc flash label need to show both incident energy and a PPE category?
No — NFPA 70E allows either method, not both. Labels can show the calculated incident energy (in cal/cm²) with the corresponding working distance, or a PPE category from Table 130.7(C)(15)(c). Mixing the two methods on the same label is not recommended and can cause confusion.
What makes an arc flash label non-compliant?
Common reasons include: missing the arc flash boundary distance, no study date, no working distance listed alongside incident energy values, PPE categories that no longer match the current study, and labels that are faded, damaged, or illegible. A label that only says “DANGER: Arc Flash Hazard” without specific values is not compliant.
Who is responsible for ensuring arc flash labels are current?
The facility owner or employer has the responsibility under NFPA 70E to ensure that equipment is labelled and that labels reflect the current arc flash study. A qualified electrical engineer typically produces compliant labels as a deliverable of the arc flash study itself.