FST Smoke Detection 2 — Questions and Answers
Question 1: Which smoke detector type is MOST prone to false alarms from cooking steam and high humidity?
- Photoelectric
- Ionization (Correct answer)
- Dual-sensor
- Air-sampling
Correct answer: Ionization
Ionization detectors are more sensitive to small combustion particles and can be triggered by steam and high-humidity environments common near kitchens.
Question 2: What is the maximum spacing allowed between smoke detectors on a smooth ceiling under NFPA 72 when no other factors apply?
- 15 feet
- 20 feet
- 30 feet (Correct answer)
- 50 feet
Correct answer: 30 feet
NFPA 72 specifies a maximum 30-foot spacing between smoke detectors on smooth ceilings under standard conditions.
Question 3: A Very Early Warning Fire Detection (VEWFD) system using air-sampling is BEST suited for which environment?
- Residential bedrooms
- Clean rooms and data centers (Correct answer)
- Open parking garages
- Outdoor loading docks
Correct answer: Clean rooms and data centers
Air-sampling VEWFD systems are ideal for clean rooms and data centers where extremely early detection is critical and the environment is controlled.
Question 4: Under NFPA 72, what is the required detector placement distance from a ceiling-mounted HVAC supply air diffuser?
- At least 12 inches
- At least 18 inches
- At least 24 inches
- At least 36 inches (Correct answer)
Correct answer: At least 36 inches
NFPA 72 requires smoke detectors to be placed at least 36 inches from HVAC supply air diffusers to prevent airflow from diluting smoke and causing delayed detection.
Question 5: Which condition describes 'stratification' as it relates to smoke detection?
- Smoke trapped below a false ceiling
- Smoke rising and cooling before reaching ceiling detectors (Correct answer)
- Smoke spread along a floor due to high density
- Smoke diluted by HVAC return air
Correct answer: Smoke rising and cooling before reaching ceiling detectors
Stratification occurs when rising smoke cools and becomes neutrally buoyant before reaching ceiling-mounted detectors, preventing activation.
Question 6: A projected beam smoke detector is MOST effective for protecting which type of space?
- Small utility closets
- Large open areas with high ceilings like warehouses (Correct answer)
- Residential hallways
- Below raised computer floors
Correct answer: Large open areas with high ceilings like warehouses
Projected beam smoke detectors are ideal for large open spaces with high ceilings because they cover long distances without requiring multiple point detectors.
Question 7: What does 'sensitivity drift' mean in the context of smoke detector maintenance?
- A detector activating only during the night cycle
- A gradual change in a detector's response threshold over time due to contamination (Correct answer)
- A detector shifting its coverage zone due to airflow
- A wiring fault causing intermittent signals
Correct answer: A gradual change in a detector's response threshold over time due to contamination
Sensitivity drift refers to a gradual shift in a detector's alarm threshold caused by dust, debris, or aging components, requiring periodic testing and cleaning.
FST Smoke Detection 2
Which smoke detector type is MOST prone to false alarms from cooking steam and high humidity?