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Fire Protection Systems- Detection/Alarm Systems
Central Station Fire Alarm Systems
This is a type of fire alarm system whereby all system functions are centralized. This means that all signals are sent to and from one central point where they are acted upon and monitored by trained and competent staff (Jones, 2009).
Shunt-Type Auxiliary Fire Alarm Systems
These systems are connected to the municipal fire alarm circuits and from this source supply electric power to the alarm systems of various buildings (Jones, 2009).
Household Fire Alarm System
This system makes use of a fire control panel for its functionality. This includes interconnection of equipment or devices, surveillance and response and power source (Jones, 2009).
Municipal Fire Alarm System
It encompasses a municipal transmission center that receives all broadcast signals. This system requires the use of a manually operated device located in buildings to be able to send signals to the municipal transmission center (Jones, 2009).
Protected Premises Fire Alarm System
This is a system that provides sound or visual alerts when there is a malfunction in the system, when there is need to give distress alerts whenever there is a fire emergency that requires attention from the fire department or when there is a surveillance and monitoring problem in the system (Jones, 2009)
Emergency Voice/Alarm Communications
This is a system that if installed into or part of an enclosure is able to broadcast sound or alarm signals, live or pre-recorded, thus ensuring prompt communication (Jones, 2009).
Auxiliary Fire Alarm System
These are fire alarm systems that are connected to the municipal transmitting devices and therefore use the municipal communications systems (Jones, 2009)
Proprietary Supervising Station Fire Alarm System
These is a system comprising of many fire alarm systems located in a single or various locations where trained personnel commissioned by property owners continually monitor and carry out surveillance on all signals emanating from the respective properties (Jones, 2009)
Remote Supervising Station Fire Alarm System
This is a type of fire alarm system where signals broadcast are received and acted upon by the trained personnel from a remote place (Jones, 2009)
Initiating Devices
These consist of hardware devices that are interconnected to activate a fire alarm and other signals either through a manual or automatic mechanism (Jones, 2009)
Notification Devices
These consist of hardware devices that are interconnected to give signals; either sound or visual signals, to give notify occupants of protected premise or fire department of impending fire dangers. (Jones, 2009)
Question 1
Ionization alarms use radioactive materials to ionize air in the sensor chamber. This ionized air serves as a conductor for electric current between two electrodes located in the same chamber. When there is fire and consequently smoke is produced, the smoke enters the chamber, interfering with the flow of electric current. This decreases it, up to a certain point where the fire alarm is triggered to notify the occupants.
Photoelectric smoke alarms use light beams generated by a light emitting diode located in the sensor chamber. When there is smoke, the light beam detects this smoke and triggers an alarm for the occupants to be notified.
In summary, ionizing smoke alarms detect smoke through reduced electrical current flow while photoelectric alarms use light sensitive sensors.
Question 2
Bedroom Smoke Alarm:
Minimum decibel ratings (NFPA Guidelines) 15dB
Ambient noise level for the bedroom 60dB
Minimum decibel ratings for bedroom smoke alarm: 15dB+60dB= 75dB.
Corridor Smoke Alarm:
Minimum decibel ratings (NFPA Guidelines) 15dB
Reduced noise level due to the door 25dB
Ambient noise level for the bedroom 60dB
Minimum decibel ratings for the corridor smoke alarm: 15dB+25dB+60dB=100dB.
Question 3
When renovating, the owner must install alarms inside and outside every sleeping room. The minimum noise level for an alarm in a sleeping room should be 75dB and 15dB above the ambient sound level. Low frequency alarms should be installed for residences habited by individuals with hearing problems. For a manually triggered process, for example when using a keypad, the number of fake distress calls sounded can be curbed by requiring the use of two buttons simultaneously or pressing a button several times in succession.
Question 4
Number of detectors (length) = 1542/50=30.84
30.84 is approximately equal to 31 (it is impossible to have a fractional number of smoke detectors)
Spacing between the detectors (Sactual) = 1542/31=49.7 ft
Distance to the wall = ½ Sactual= (1/2) * 49.7 ft=24.8 ft.
Number of detectors (width) =6/5.0=1.2
1.2 is approximately equal to 1.
Sactual=6/1=6 ft.
Distance to the wall = ½ Sactual= (1/2) * 6=3 ft.
Question 5
According to the NFPA 72 Guidelines, the furthest distance from the ceiling that spot type detector can be placed is 12 inches. This is because the detector is well placed and prevents the installation of other unnecessary detectors.
Question 6
According to the NFPA Guidelines, the furthest distance that the detector should be placed from the peak of such a building is 3 feet. This is also because it prevents the installation of unwanted detectors.
Question 7
Class A: Ordinary combustibles for example paper
Class B: Flammable liquids for example petroleum
Class C: Energized Electrical Equipment for example microwave
Class D: Metals for example sodium
Class K: Fires involving combustible cooking media such as cooking oil
Question 8
The fire tetrahedron comprises four components, which include heat, fuel, uninhibited chemical chain reactions and oxidizing agent. It is imperative for fire protection professionals to be aware of these components because that is the only way they can understand the rationale for using various strategies for dismantling the fire tetrahedron as part of their fire-fighting efforts.
References
Jones, A.M. (2009). Fire protection systems. Clifton Park, NY: Cengage Learning.
