IEC Electrical Safety Practices 4 — Questions and Answers
Question 1: Which type of fire extinguisher is appropriate for use on an energized electrical fire?
- Class A (water-based)
- Class B (CO2 or dry chemical)
- Class C (CO2, dry chemical, or halon) (Correct answer)
- Class D (dry powder)
Correct answer: Class C (CO2, dry chemical, or halon)
Class C extinguishers use non-conductive agents such as CO2, dry chemical, or halon, making them safe for use on energized electrical fires.
Question 2: What is the purpose of a Job Hazard Analysis (JHA) before beginning electrical work?
- To satisfy billing and insurance documentation requirements
- To systematically identify hazards associated with each task step and implement controls before work begins (Correct answer)
- To assign liability in case of an accident
- To document which tools will be used
Correct answer: To systematically identify hazards associated with each task step and implement controls before work begins
A JHA breaks each task into steps, identifies potential hazards at each step, and establishes controls to eliminate or reduce those hazards before work starts.
Question 3: What is 'step potential' and why is it dangerous near downed power lines?
- The voltage drop across each rung of a ladder
- A voltage gradient in the ground that can drive current through a person's legs when stepping (Correct answer)
- The required step-down transformer voltage ratio
- The potential energy stored in a capacitor bank
Correct answer: A voltage gradient in the ground that can drive current through a person's legs when stepping
Step potential is a voltage gradient in the ground near a fault point; current can flow through a person's legs when one foot is at a higher potential than the other.
Question 4: Under OSHA 29 CFR 1910.147, which energy source type is NOT covered by the Lockout/Tagout standard?
- Pneumatic energy
- Hydraulic energy
- Electrical energy
- Hot water systems under normal household pressure below OSHA's scope threshold (Correct answer)
Correct answer: Hot water systems under normal household pressure below OSHA's scope threshold
OSHA 1910.147 covers electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and gravitational energy; however, small residential systems below threshold are outside its industrial scope.
Question 5: What is the function of a Ground Fault Circuit Interrupter (GFCI) in electrical safety?
- Protects conductors from overcurrent damage
- Interrupts power when it detects a current imbalance of 5 milliamps or more between line and neutral (Correct answer)
- Prevents voltage surges from damaging equipment
- Provides equipment grounding in the absence of a ground wire
Correct answer: Interrupts power when it detects a current imbalance of 5 milliamps or more between line and neutral
A GFCI monitors the current difference between line and neutral and trips within milliseconds when an imbalance of approximately 5 mA is detected, preventing electrocution.
Question 6: What is the correct action when a worker discovers a tag-only (tagout) device on an energy isolation point but no lockout device?
- Remove the tag and proceed — tags have no legal standing
- Treat the tag as equivalent to a lock and proceed cautiously
- Do not operate the energy isolating device; contact the authorized employee who applied the tag (Correct answer)
- Replace the tag with a lock immediately
Correct answer: Do not operate the energy isolating device; contact the authorized employee who applied the tag
Tags are warning devices only; you must not operate an energy isolation point with a tag — contact the authorized employee who applied it before any action.
Question 7: Which document formally establishes the boundaries, hazards, and required PPE for an electrical task before work begins under NFPA 70E?
- Job Safety Analysis (JSA) only
- Energized Electrical Work Permit (Correct answer)
- Equipment manufacturer's operating manual
- OSHA 300 log entry
Correct answer: Energized Electrical Work Permit
An Energized Electrical Work Permit formally documents the justification, hazards, boundaries, and PPE required when work must be performed on energized equipment.
