NFPA 70E has established approach boundaries to protect employees working on or near energized equipment. These boundaries define safe working distances and necessary precautions. The Informative Annex C of NFPA 70E provides an illustration of these limits, which are outlined below:

- Arc Flash Protection Boundary (outer boundary) – The farthest boundary from the energized equipment. If an arc flash occurs, this is where a worker could receive a first-degree burn. Workers must not cross this boundary without proper electrical Personal Protective Equipment (PPE).
- Limited Approach – The distance at which barriers should be placed to protect personnel. This boundary is set to minimize exposure to a shock hazard near an exposed live part.
- Restricted Approach – A high-risk area where only qualified personnel are permitted. Proper PPE is required based on the necessary level of protection.
- Prohibited Approach (inner boundary) – A distance equivalent to direct contact with live components. Previously included in NFPA 70E, this boundary was removed in the 2015 edition.
The required approach limits vary based on the type of equipment, as some may have a larger or smaller flash protection boundary.
2 Minute Toolbox Talk: NFPA 70E – Arc Flash Safety
The 4 P’s Model for Arc Flash Hazard Management
An effective strategy for preventing arc flashes is the 4 P’s Model: Predict, Prevent, Protect, Publish.
Predict – Identify and calculate potential risks through an arc flash study. The IEEE 1584 Guide for Performing Arc Flash Hazard Calculations (2002) is recommended for assessing arc flash severity.
Prevent – Reduce risk by following the hierarchy of controls, incorporating safety measures into design and planning, and eliminating hazards where possible.
Protect – If a hazard cannot be eliminated, mitigate risk using proper PPE and protective measures.
Publish – Document risk assessments, use findings for training, and apply safety warning labels where risks remain.

Arc Flash Warning Labels
Per NFPA 70E, energized equipment must display warning labels, such as arc flash stickers (electrical hazard labels), to alert workers to potential dangers.
The 2017 edition of NFPA 70®: National Electrical Code (NEC) specifies in Article 110.16:
“Electrical systems such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers (except in dwellings) that require examination, adjustment, servicing, or maintenance while energized must be field- or factory-marked to warn qualified persons of potential arc flash hazards. The marking shall be clearly visible before servicing the equipment.”
Labels must include:
- Nominal system voltage
- Fault current at the service overcurrent device
- Clearing time of the service overcurrent protective device
- Installation date of the label
As labeling standards evolve under NFPA 70E, workers must ensure labels provide clear, essential safety information.
Arc Flash Warning Label Components
- Danger or Warning Header
- Working Distance – Distance from the arc source
- Incident Energy – Thermal energy at working distance
- Arc Flash Boundary – Distance where a second-degree burn could occur without protection
- “Shock Hazard When Cover is Removed” – Voltage level of the equipment
- Limited Approach Boundary
- Restricted Approach Boundary
- Glove Class – Proper rubber-insulated gloves required
- PPE Category Requirement – Appropriate arc flash protection gear

Personal Safety & Protective Equipment (PPE)
A key update in NFPA 70E is the inclusion of the hierarchy of controls, emphasizing that hazard elimination should always be the top priority. Performing energized work while relying solely on PPE should be considered a last resort.
Arc Flash PPE Categories (NFPA 70E)
NFPA 70E classifies PPE into four categories, each with a minimum Arc Rating requirement. Selecting the correct PPE is critical to worker safety.

By following NFPA 70E guidelines and implementing the Limits of Approach, 4 P’s Model, and proper warning labels, workplaces can significantly reduce the risk of arc flash incidents. Until next time…Work Safe & Be Safe!