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Arc Flash Labelling

The labels are required to include the following information

  • Nominal system voltage.
  • Fault current at the service overcurrent device.
  • Clearing time of service overcurrent protective devices based on available fault current at the service equipment.
  • Date of label installation.

1. Danger or Warning Header

The “Danger” header is typically used when the voltage exceeds 600 or when the incident energy exceeds 40 cal/cm2. If it falls below this threshold, an orange “Warning” header is commonly employed.

4. Live working zone DL in accordance with EN 50110

The live working zone is a zone surrounding live parts. The outer boundary of this zone is measured from the live part. The distance DL applies to the outer boundary of the zone. Live working is all work where the worker either makes contact with live parts or is inside or reaches with parts of the body or with tools, equipment and devices being handled into this zone.

7. Incident energy

The amount of thermal energy impressed on a surface, a certain distance from the source,
generated during an electric arc event.

1. The incident energy is calculated at the working distance. Incident energy increases as the distance from the potential arc source decreases, and the incident energy decreases as the distance increases.

2. The units used to measure incident energy are joules per square centimeter (J/cm 2 ) or calories per square centimeter (cal/cm2) (refer to IEEE1584-2018).

2. The voltage of the equipment

This refers to the electrical potential difference of the equipment, which is a measure of the force that drives electric current through a circuit.

5. Working distance

The distance between the potential arc source and the face and chest of the worker
performing the task.

Parts of the body closer to the potential arc source other than the face and chest receive a greater incident energy.
The arc source is usually energized parts within an equipment enclosure or exposed energized parts in open air. (refer to IEEE1584-2018).

8. Hazard Risk Category

Different levels of protection are required for each hazard risk category, ranging from 1 to 4. Category ``0`` was eliminated in the 2015 NFPA 70E changes.

3. Vicinity zone Dv in accordance with EN 50110

The vicinity zone is a zone surrounding a live working zone. The outer boundary of this zone is measured from live part. The distance Dv applies to the outer bounder of the zone. The distance from the live working zone boundary DL to the outer boundary of the vicinity zone depends upon the voltage of the live part. Work in the vicinity is all work where a worker is either inside or reaches with parts of the body, or tools, equipment and devices being handled, into this zone but does not reach into the live working zone.

6. Arc flash boundary

The distance from a prospective arc source at which the incident energy is calculated to be
5.0 J/cm 2 (1.2 cal/cm 2 ).(refer to IEEE1584-2018)
The shortest distance at which a person working during an arc flash incident may sustain permanent injury, typically the onset of a second-degree burn or worse, if not adequately protected by flame-resistant (FR) clothing.

1. Danger or Warning Header

The “Danger” header is typically used when the voltage exceeds 600 or when the incident energy exceeds 40 cal/cm2. If it falls below this threshold, an orange “Warning” header is commonly employed.

2. The voltage of the equipment

This refers to the electrical potential difference of the equipment, which is a measure of the force that drives electric current through a circuit.

3. Vicinity zone Dv in accordance with EN 50110

The vicinity zone is a zone surrounding a live working zone. The outer boundary of this zone is measured from live part. The distance Dv applies to the outer bounder of the zone. The distance from the live working zone boundary DL to the outer boundary of the vicinity zone depends upon the voltage of the live part. Work in the vicinity is all work where a worker is either inside or reaches with parts of the body, or tools, equipment and devices being handled, into this zone but does not reach into the live working zone.

4. Live working zone DL in accordance with EN 50110

The live working zone is a zone surrounding live parts. The outer boundary of this zone is measured from the live part. The distance DL applies to the outer boundary of the zone. Live working is all work where the worker either makes contact with live parts or is inside or reaches with parts of the body or with tools, equipment and devices being handled into this zone.

5. Working distance

The distance between the potential arc source and the face and chest of the worker
performing the task.

Parts of the body closer to the potential arc source other than the face and chest receive a greater incident energy.
The arc source is usually energized parts within an equipment enclosure or exposed energized parts in open air. (refer to IEEE1584-2018).

6. Limited Approach and Restricted Approach Fields

These fields pertain to Shock Hazard Approach Boundaries, which are further elucidated in our Arc Flash Workplace Safety Guide. The ``prohibited approach`` boundary was removed in the 2015 edition of NFPA 70E.

7. Incident energy

The amount of thermal energy impressed on a surface, a certain distance from the source,
generated during an electric arc event.

1. The incident energy is calculated at the working distance. Incident energy increases as the distance from the potential arc source decreases, and the incident energy decreases as the distance increases.
2. The units used to measure incident energy are joules per square centimeter (J/cm 2 ) or calories per square centimeter (cal/cm2) (refer to IEEE1584-2018).

8. Hazard Risk Category

Different levels of protection are required for each hazard risk category, ranging from 1 to 4. Category ``0`` was eliminated in the 2015 NFPA 70E changes.


Labels must be produced and attached to electrical equipment outlined within the study’s scope as mandated by codes and regulations. This equipment should encompass, at minimum, utility company or customer-owned transformers, switchgear, switchboards, panel boards, industrial control panels, meter socket enclosures, adjustable speed drives, machine control panels, and motor control centers. Additionally, the scope may encompass equipment such as busways, bus plugs, fused and non-fused disconnect switches, and motor terminal boxes, among others.

Arc flash labels need to be conspicuously positioned on the electrical equipment. Placement examples include:

  1. On the front cover of the equipment.
  2. On the exterior of the equipment enclosure.
  3. On the breaker door of a switchboard or panelboard.
  4. On the external surface of the control cabinet for an industrial control panel.

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