F89 Fire Protection Systems 3 — Questions and Answers
Question 1: What is the difference between a wet-pipe and dry-pipe sprinkler system?
- Wet-pipe uses foam; dry-pipe uses water
- Wet-pipe has water constantly in the pipes; dry-pipe has pressurized air until activation (Correct answer)
- There is no difference; both terms describe the same system
- Wet-pipe is for indoor use; dry-pipe is for outdoor use only
Correct answer: Wet-pipe has water constantly in the pipes; dry-pipe has pressurized air until activation
A wet-pipe system has water under pressure in the pipes at all times, while a dry-pipe system has pressurized air that holds water back until a sprinkler head activates.
Wet-pipe sprinkler systems have water under pressure filling the piping at all times. When a sprinkler head activates, water discharges immediately. Dry-pipe systems have pressurized air in the piping. When a sprinkler head activates, air escapes, the valve opens, and water fills the pipes. Dry-pipe systems are used in areas subject to freezing.
Question 2: What is the purpose of a fire pump in a high-rise building's fire protection system?
- To drain water from the sprinkler system after activation
- To boost water pressure to ensure adequate flow to sprinklers and standpipes at upper floors (Correct answer)
- To pump water out of the building during flooding
- To supply water to the building's domestic plumbing system
Correct answer: To boost water pressure to ensure adequate flow to sprinklers and standpipes at upper floors
Fire pumps boost water pressure to overcome the elevation head in tall buildings, ensuring adequate pressure and flow at upper floors.
In high-rise buildings, municipal water supply pressure is insufficient to deliver adequate water flow to upper floors. Fire pumps boost water pressure to overcome the static elevation head plus friction losses. NYC Building Code requires fire pumps in buildings where the highest sprinkler or standpipe is above the reach of city water pressure.
Question 3: What does NFPA 25 govern and why is it important to the FLSD?
- Installation of new fire alarm systems
- Inspection, testing, and maintenance of water-based fire protection systems (Correct answer)
- Building construction fire ratings
- Fire department emergency response procedures
Correct answer: Inspection, testing, and maintenance of water-based fire protection systems
NFPA 25 establishes the standards for inspection, testing, and maintenance of water-based fire protection systems including sprinklers, standpipes, and fire pumps.
NFPA 25 provides comprehensive requirements for ensuring that installed sprinkler, standpipe, fire pump, and water storage systems remain functional throughout their service life. It specifies inspection frequencies, testing protocols, and maintenance requirements. NYC Fire Code incorporates NFPA 25 requirements.
Question 4: What is the function of a standpipe system's pressure reducing valve (PRV)?
- To increase water pressure at lower floors
- To reduce excessive water pressure at lower floors to safe, usable levels for fire department hose lines (Correct answer)
- To prevent water hammer in the piping
- To regulate the fire pump speed
Correct answer: To reduce excessive water pressure at lower floors to safe, usable levels for fire department hose lines
PRVs at lower floor standpipe outlets reduce excessive pressure caused by elevation to safe operating levels for fire department hose streams.
In high-rise standpipe systems, the water pressure at lower floors can be dangerously high. Pressure reducing valves installed at standpipe hose outlets on lower floors reduce the pressure to safe, controllable levels. The FLSD must ensure PRVs are included in the regular inspection and testing program.
Question 5: What type of fire alarm system initiating device uses a photoelectric or ionization sensor?
- Manual pull station
- Smoke detector (Correct answer)
- Heat detector
- Waterflow switch
Correct answer: Smoke detector
Smoke detectors use either photoelectric (light-scattering) or ionization technology to detect smoke particles in the air.
Smoke detectors use one of two primary sensing technologies: photoelectric detectors use a light source and photosensitive sensor — smoke particles scatter the light beam, triggering the alarm. Ionization detectors contain a small amount of radioactive material that ionizes air — smoke particles disrupt this current, triggering the alarm. Many modern detectors combine both technologies.
Question 6: What is the required inspection frequency for sprinkler system control valves according to NFPA 25?
- Annually
- Monthly
- Weekly (Correct answer)
- Daily
Correct answer: Weekly
NFPA 25 requires weekly inspection of sprinkler system control valves to verify they are in the open position and properly secured.
NFPA 25 requires that all sprinkler system control valves be visually inspected weekly to verify they are fully open, properly sealed or locked, and that tamper switches are functioning. A closed control valve is one of the most common causes of sprinkler system failure. Electronically supervised valves may have their physical inspection frequency reduced to monthly.
F89 Fire Protection Systems 3
What is the difference between a wet-pipe and dry-pipe sprinkler system?