FST Electrical Fire Safety 2 — Questions and Answers
Question 1: Which condition is most directly responsible for insulation failure that leads to arc faults in building wiring?
- Damaged, aged, or compressed wiring insulation (Correct answer)
- High ambient humidity levels in electrical rooms
- Using 12 AWG wire on a 15-amp circuit
- Reverse polarity at duplex receptacle outlets
Correct answer: Damaged, aged, or compressed wiring insulation
Physical damage, aging, heat exposure, and compression degrade conductor insulation over time, allowing conductors to contact each other or nearby combustibles and arc, potentially starting fires.
Question 2: What is the primary electrical fire hazard associated with aluminum branch circuit wiring in older residential buildings?
- Aluminum oxidizes at connections, increasing resistance and generating dangerous heat (Correct answer)
- Aluminum conductors cannot carry sufficient current for typical household loads
- Aluminum wire is far more susceptible to arc faults than copper wire
- Aluminum has a higher melting point than copper, masking signs of overheating
Correct answer: Aluminum oxidizes at connections, increasing resistance and generating dangerous heat
Aluminum forms an oxide layer at connections that significantly increases electrical resistance, generating heat at termination points that can ignite combustibles and cause fires.
Question 3: When performing a fire safety inspection of an electrical room, which finding represents the most immediate fire risk?
- Combustible materials stored inside the electrical room (Correct answer)
- Missing knockout plugs in unused panel openings
- Conduit runs that lack identification labels
- Light fixtures installed without lens diffusers
Correct answer: Combustible materials stored inside the electrical room
Combustible materials stored in electrical rooms create an extreme fire hazard because electrical arcs, sparks, or overheated equipment can readily ignite them in an area difficult to reach for suppression.
Question 4: Extension cords used as permanent wiring represent a fire hazard primarily because:
- They are not designed for continuous use and may overheat over extended periods (Correct answer)
- Their insulation is rated for higher voltages than standard branch circuit wiring
- They cannot be protected by standard household circuit breakers
- They introduce grounding problems in all three-wire grounded circuits
Correct answer: They are not designed for continuous use and may overheat over extended periods
Extension cords are designed for temporary, occasional use and lack the protection of permanent wiring; continuous use causes insulation degradation and overheating, which can ignite surrounding materials.
Question 5: What does the term 'thermal runaway' refer to in the context of electrical fire safety?
- A self-reinforcing cycle where increased temperature causes greater resistance, generating even more heat (Correct answer)
- The rapid spread of fire through electrical conduit pathways in a building
- The process by which electrical equipment cools down safely after emergency shutdown
- Voltage fluctuations caused by excessive electrical loads on a single circuit
Correct answer: A self-reinforcing cycle where increased temperature causes greater resistance, generating even more heat
Thermal runaway occurs when rising temperatures increase resistance, generating more heat, which further increases temperature in a dangerous positive feedback loop that can destroy equipment and cause fires.
Question 6: A 'daisy-chained' power strip (one power strip plugged into another) is a fire hazard primarily because:
- It can exceed the circuit's ampacity and the individual strips' ratings simultaneously (Correct answer)
- It increases the available voltage to all connected equipment
- It bypasses the GFCI protection installed on the outlet circuit
- It prevents proper grounding of all devices connected downstream
Correct answer: It can exceed the circuit's ampacity and the individual strips' ratings simultaneously
Daisy-chaining power strips allows connection of far more devices than the circuit or original strip was designed to support, leading to overloading, overheating, and potential fire.
Question 7: Which NFPA standard specifically addresses electrical safety requirements in the workplace, including arc flash hazard analysis and personal protective equipment?
- NFPA 70E (Correct answer)
- NFPA 72
- NFPA 13
- NFPA 101
Correct answer: NFPA 70E
NFPA 70E, Standard for Electrical Safety in the Workplace, addresses arc flash, shock, and blast hazards, requiring employers to perform hazard analysis and provide appropriate PPE for electrical workers.
FST Electrical Fire Safety 2
Which condition is most directly responsible for insulation failure that leads to arc faults in building wiring?