CSLB C-10 Electrical ContractorSafety and TestingMedium
According to NFPA 70E, what is the primary purpose of an Arc Flash Boundary (AFB)?
- ATo indicate the distance at which an exposed person could receive a second-degree burn.
- BTo specify the distance from live parts where insulated tools are required.
- CTo establish the boundary where arc blast overpressure could cause injury.
- DTo define the minimum approach distance for unqualified persons.
Show answer & explanationAnswer & explanation
Correct answer: A. To indicate the distance at which an exposed person could receive a second-degree burn.
The Arc Flash Boundary (AFB) is defined by NFPA 70E as the distance from an arc source at which an unprotected person could receive a second-degree burn. This boundary dictates when arc-rated personal protective equipment (PPE) is required.
Why the other options are wrong
- B. Insulated tools are required within the Restricted Approach Boundary, which is closer than the AFB.
- C. While arc blast is a hazard, the AFB specifically relates to thermal injury (second-degree burn).
- D. This describes the Limited Approach Boundary, not the Arc Flash Boundary.
Arc Flash Boundary (AFB)
An imaginary boundary around energized electrical equipment, defined by NFPA 70E, where the incident energy of an arc flash is 1.2 cal/cm² (the onset of a second-degree burn).
- Requires arc-rated PPE for entry.
- Protects against thermal effects of an arc flash.
- Determined through an arc flash risk assessment.
Memory trick: Approach Carefully, Restricted Zone, Flash Hazard Ahead!