ASP Electrical Safety 2 — Questions and Answers
Question 1: Which of the following best describes the 'arc flash boundary' according to NFPA 70E?
- The distance at which the incident energy equals 1.2 cal/cm², the onset of a second-degree burn (Correct answer)
- The distance a worker must stand from any electrical panel
- The area requiring arc-rated clothing rated at PPE Category 4
- The boundary within which only licensed electricians may work
Correct answer: The distance at which the incident energy equals 1.2 cal/cm², the onset of a second-degree burn
The arc flash boundary is the distance from an arc source at which the incident energy decreases to 1.2 cal/cm², the threshold for a curable second-degree burn.
Question 2: Under NFPA 70E, an Energized Electrical Work Permit is required when:
- Work must be performed on or near exposed energized electrical conductors and the equipment cannot be de-energized (Correct answer)
- Any worker enters a room containing electrical panels
- Replacing a light bulb in an energized fixture
- Testing a de-energized circuit with a voltmeter
Correct answer: Work must be performed on or near exposed energized electrical conductors and the equipment cannot be de-energized
An Energized Electrical Work Permit is required whenever work must be done on energized conductors that cannot feasibly be de-energized, documenting the justification and controls.
Question 3: Electrical equipment located in a Class I, Division 1 hazardous location contains:
- Flammable gases or vapors present in ignitable concentrations under normal operating conditions (Correct answer)
- Combustible dust that can ignite when suspended in air
- Ignitable fibers or flyings that are handled or stored on the premises
- Radioactive materials requiring special shielding
Correct answer: Flammable gases or vapors present in ignitable concentrations under normal operating conditions
Class I, Division 1 locations are those where flammable gases or vapors exist in ignitable or explosive concentrations under normal operating conditions.
Question 4: The primary cause of electrical fires in the workplace is:
- Overloaded circuits, damaged wiring, or loose connections generating heat (Correct answer)
- Improper use of personal protective equipment
- Failure to install GFCI protection in wet locations
- Use of extension cords with three-prong plugs
Correct answer: Overloaded circuits, damaged wiring, or loose connections generating heat
Overloaded circuits, deteriorated wiring insulation, and loose connections are the leading causes of electrical fires because they create heat that can ignite nearby combustibles.
Question 5: What does the 'hierarchy of controls' recommend as the most effective means of protecting workers from electrical hazards?
- Elimination of the hazard by de-energizing equipment before work begins (Correct answer)
- Providing arc-rated PPE to all electrical workers
- Installing warning signs near electrical panels
- Training workers to recognize electrical hazards
Correct answer: Elimination of the hazard by de-energizing equipment before work begins
Elimination (de-energizing the equipment) is the most effective control because it removes the hazard entirely rather than just mitigating exposure to it.
Question 6: Temporary wiring used on construction sites under OSHA 29 CFR 1926.405 must be protected from damage and:
- Supported and secured in place at intervals not exceeding 10 feet for cables (Correct answer)
- Replaced every 30 days regardless of condition
- Rated at no more than 120 volts
- Used only in dry locations without GFCI protection
Correct answer: Supported and secured in place at intervals not exceeding 10 feet for cables
OSHA requires that temporary wiring on construction sites be supported and secured at intervals not to exceed 10 feet for cables to prevent damage and tripping hazards.
Question 7: Which PPE is considered the last line of defense against electrical shock and arc flash hazards?
- Arc-rated clothing, face shields, rubber insulating gloves with leather protectors, and safety footwear (Correct answer)
- Hard hats and safety glasses only
- Cotton clothing and leather gloves
- High-visibility vests and steel-toed boots
Correct answer: Arc-rated clothing, face shields, rubber insulating gloves with leather protectors, and safety footwear
Arc-rated clothing, face shields, rubber insulating gloves, and appropriate footwear form the complete PPE ensemble that protects against both shock and arc flash after engineering and administrative controls.
ASP Electrical Safety 2
Which of the following best describes the 'arc flash boundary' according to NFPA 70E?