How many protection boundaries are defined for arc flash safety?

• A. 2
• B. 4
• C. 3
• D. 5

Answer: (C)

Protection boundaries around exposed energized equipment establish how close you may work and what PPE is required. There are three boundaries typically emphasized for arc flash safety: the arc flash boundary, which marks the distance at which the incident energy is about 1.2 cal/cm² and inside which arc‑rated PPE is needed; the limited approach boundary, the distance beyond which unqualified personnel may not approach and within which only qualified persons with appropriate PPE and procedures may operate; and the restricted approach boundary, which is closer to the energized parts and may be entered only by qualified personnel with the proper PPE and training. These three boundaries create progressively safer zones and guide PPE selection and work practices. Some materials also reference a prohibited boundary, but the common count for protection boundaries in this context is three.