Arc Flash Hazard Analysis: NFPA 70E Updates You Should Know

What Is Arc Flash?

An arc flash is a sudden release of electrical energy through the air when a high-voltage gap exists and there is a breakdown between conductors. The result is an explosive release of energy that produces:

• Extreme heat - Temperatures at the arc can reach 35,000 degrees Fahrenheit, hotter than the surface of the sun
• Intense light - Capable of causing temporary or permanent blindness
• Pressure waves - The rapid expansion of air can throw workers across a room and produce sound levels exceeding 140 dB
• Shrapnel - Molten metal and vaporized copper can be expelled at high velocity

According to OSHA and NFPA data, there are an estimated 30,000 arc flash incidents per year in the United States, resulting in approximately 7,000 burn injuries, 2,000 hospitalizations, and 400 fatalities annually.

NFPA 70E: The Standard

NFPA 70E, Standard for Electrical Safety in the Workplace, is the primary standard governing electrical safety practices for employees. While the NEC (NFPA 70) covers installation requirements, NFPA 70E covers the safety of people working on or near electrical equipment after it is installed.

OSHA does not write its own electrical safety work practice standards. Instead, OSHA references and enforces NFPA 70E as the basis for compliance with electrical safety regulations in the workplace.

Key Updates in the 2024 Edition

Risk Assessment Procedure

The 2024 edition strengthens the risk assessment procedure in Article 110:

• Employers must conduct a risk assessment before any employee approaches an electrical hazard
• The assessment must identify the hazard, estimate the likelihood of occurrence, estimate the severity of injury, and determine if additional protective measures are required
• The hierarchy of risk controls has been clarified: elimination, substitution, engineering controls, awareness, administrative controls, and PPE (in that order of preference)

Updated PPE Category Tables

Table 130.7(C)(15)(a) and (b) have been revised:

• Several equipment types have been recategorized based on updated incident energy data
• Panelboards rated 240V and below have clarified PPE requirements based on available fault current
• PPE requirements for motor control centers have been updated to reflect actual incident energy levels more accurately
• The tables now more clearly distinguish between arc flash boundary distances for different equipment configurations

Arc Flash Boundary Calculations

For situations where the PPE category method is not applicable, an incident energy analysis must be performed. The 2024 edition includes:

• Updated references to IEEE 1584-2018 for incident energy calculations
• Clarified requirements for equipment labeling, including the nominal system voltage, arc flash boundary, and available incident energy or PPE category
• New guidance on how often arc flash studies must be reviewed and updated (whenever there is a change to the electrical distribution system that could affect incident energy levels)

Establishing an Electrically Safe Work Condition

NFPA 70E emphasizes that the safest approach is always to de-energize equipment before working on it. The procedure for establishing an electrically safe work condition (Article 120) includes:

1. Identify all sources of electrical supply to the equipment
2. Disconnect the load, then open the disconnecting device(s) for each source
3. Where possible, visually verify that all blades of the disconnecting devices are fully open
4. Apply lockout/tagout devices
5. Test each conductor with an adequately rated voltage detector to verify the absence of voltage
6. Ground all circuit conductors where the possibility of induced voltages or stored energy exists

What Employers Must Do

• Develop and implement an electrical safety program per Article 110
• Conduct arc flash risk assessments for all equipment where employees may be exposed
• Provide appropriate PPE at no cost to employees
• Ensure all employees are trained and qualified for the electrical work they perform
• Label all electrical equipment with arc flash hazard information
• Review and update the electrical safety program and arc flash study whenever the electrical system changes