1. Fire Alarm System Initiating Devices
Chapter 12
Page 357

2. Objectives
List and compare the available types of manually operated fire alarm devices
Discuss the methodology used to increase the reliability of a fire alarm system
Evaluate the differences between the available types of heat detectors
Compare the capabilities of the various types of smoke detectors 2

3. Objectives Define stratification and explain how it can be predicted
Propose a methodology for detecting a fire where stratification is predicted
Discuss the “pressure sandwich,” and explain how this principle is accomplished by a fire detection system 3

4. Objectives Compare and contrast flame detectors and their applications
Give examples of where gas detectors and pressure detectors are appropriate for use
List and discuss the fire protection system supervisory functions that can be provided by a fire alarm system 4

5. Manually Operated Devices
Manually operated fire alarm devices: require the action of an individual to initiate a fire alarm signal
Manual pull stations: used by building occupants to electronically notify others of a fire 5

6. Manually Operated Devices
Coded manual stations: send a set of unique time-pulsed signals to the fire alarm control unit three or more times, indicating location of the manual station
Non-coded manual stations: do not deliver a distinctive signal
Grouped on a circuit so the control unit can indicate activation 6

7. Manually Operated Devices
Presignal and General Alarm Manual Stations
Single-Action and Double-Action Manual Stations
Breakglass and Nonbreakglass Manual Stations
Addressable Manual Stations 7

8. Automatic Fire Detectors
Reliability Methodology for Detectors
Methods of ensuring the reliability of an automatic fire detection system:
Protection
Wiring
Support
Ceiling jet interaction
Testing accessibility 8

9. Automatic Fire Detectors (con’t.)
Figure Detection system support

10. Automatic Fire Detectors (con’t.)
Methods of ensuring the reliability of an automatic fire detection system (con’t.):
Enclosure evaluation
Specific points of hazard
Anticipated fire
Detection zones
Addressable Detectors 10

11. Automatic Fire Detector Overview and Comparison
Automatic fire detectors are composed of
Heat-sensing fire detectors
Smoke-sensing fire detectors
Flame-sensing radiant energy fire detectors
Gas-sensing detectors
Pressure detectors
Non-fire detectors (cold detectors, video surveillance systems) 11

12. Automatic Fire Detector Overview and Comparison (con’t.)
Table Comparison of automatic fire detectors

13. Spot-Type Heat-Sensing Fire Detectors
Spot-Type Pneumatic Rate-of-Rise Heat Detectors
Spot-Type Thermocouple Rate-of-Rise Heat Detectors
Spot-Type Fixed Temperature Heat Detectors
Spot-Type Rate-Compensated Heat Detectors 13

14. Spot-Type Heat-Sensing Fire Detectors (con’t.)
Figure Spot-type pneumatic rate-of-rise heat detector

15. Spot-Type Heat-Sensing Fire Detectors (con’t.)
Figure Bimetallic fixed temperature heat detectors

16. Spot-Type Heat-Sensing Fire Detectors
Spot-Type Electronic Thermistor Heat Detectors
Spot-Type Analog Heat Detectors
Spot-Type Combination Heat Detectors 16

17. Line-Type Heat-Sensing Devices
Electric or pneumatic
Can be selected to detect either a fixed- temperature or rate-of-temperature rise anywhere along the length of the detector
Well suited for linear or elongated hazards such as conveyors and electric cable trays 17

18. Smoke-Sensing Fire Detectors
Spot-Type Ionization Smoke Detectors
Spot-Type Photoelectric Light-Scattering Detectors
Spot-Type Photoelectric Light Obscuration Smoke Detectors
Air-Sampling or Air-Aspirated Smoke Detectors
Laser-Based Air Sampling Smoke Detectors 18

19. Smoke-Sensing Fire Detectors
Figure Line-type heat-sensing device: applications
(Note: These detectors are ideal for linear or elongated hazards such as conveyors and cable trays) 19

20. Smoke-Sensing Fire Detectors
Linear Beam Smoke Detectors
Air-Duct Smoke Detectors
Analog Smoke Detectors 20

21. Flame-Sensing Radiant Fire Detectors
Ultraviolet (UV) Flame Detectors
Infrared (IR) Flame Detectors
Combination Ultraviolet/Infrared (UV/IR) Detectors
Selecting a Flame Detection System
Radiation Spectrum for Flame Detectors
Inverse Square Law for Flame Detectors
Spark/Ember Detectors 21

22. Flame-Sensing Radiant Fire Detectors (con’t.)
Figure Radiation spectrum

23. Multi-Sensor Detectors
Multi-sensor detectors: increases reliability by combining heat and smoke sensing, heat and carbon monoxide sensing, heat/co/smoke sensing, or ionization plus photoelectric sensing
Multi-sensor detectors contain algorithms for discerning sources of nuisance alarms 23

24. Gas-Sensing Detectors
A gas-sensing detector can be chosen to detect the release of a flammable gas before it reaches ignitable concentration
Gas-sensing detectors: detect the release of a flammable gas before it reaches ignitable concentration 24

25. Pressure-Sensing Fire Detectors
In tightly enclosed rooms or enclosures where personnel are not present, a fire increases the pressure in the enclosure
Pressure-sensing fire detector: plate that depresses when the enclosure pressure increases to a predetermined level and activates a signal to the FACU 25

26. Fire Protection System Flow And Supervisory Switches
Sprinkler System Waterflow Switches
Fire Suppression System Releasing Switches
Fire Suppression System Supervisory Switches 26

27. Summary
Initiating devices on a fire alarm system are watchdogs that supervise essential equipment and report fire conditions to the fire alarm control unit (FACU)
Initiating devices must be
Protected
Properly wired and supported
Placed within the ceiling jet boundary 27

28. Summary Initiating devices must (con’t.):
Tested frequently and suitable in the enclosure conditions to which it is exposed
Installed for specific points of hazard
Selected correctly for the anticipated fire
Zoned wisely 28

29. Summary Detectors types Heat-sensing Smoke-sensing Particle-sensing
Flame-sensing
Gas-sensing
Pressure-sensing 29