Fire Fighting Notes

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Prevent
• Make sure it do not start • Control fuel sources

Communicate
• Ensure if fire happens, occupants know what to do

Escape
• Provide a route for escape for occupant to move safely before threatened by smoke

Containment
• Ensure fire can be contained to smallest possible area

Extinguishment
• Ensure fire can be extinguished quickly with minimum damage

FIRE DETECTION SYSTEM

SMOKE DETECTORS

HEAT DETECTOR

FLAME DETECTOR

GAS SENSING DETECTOR

Ionisation Dectectors

Fixed Temperature Detector

Infrared Flame Detector

Infrared Flame Detector

Photolectic Detector

Rate Compensation Detector

Ultra Violet Detector

Ultraviolet detector

Rate of Rise Dectector

SMOKE DETECTOR

IONISATION TYPE
-flaming fire

PHOTOLECTIC TYPE
- smouldering fire

Ionise air with small amount of radioactive material

Projected beam type

Spot type

Cloud chamber

Produces small amt of electrical currect that flows thru air in chamber

light projected across protected area

light scattering principles

Use air sampling system consist of a tube network

Spot type, mounted on ceiling

smoke particles that obscure the light beam reduces light intensity thus initiate signal

smoke enter unit causes reflected light to strike photoelectic cell

air draws into humidity chamber

More responsive to combustion particles than large particles

detector should be enclosed so movement of object would not cause false alarm

more smoke / large particles = reflect more light

moisture in chamber condeneses smoke particles forming a cloud

can be located several fts below ceiling if there is hgiht ceiling

cloud density measured by photoelectic principle

denser than predetermined level = alarm initiated.

allow smaller smoke particles to be detected. cumbersome, need to maintain and pump.

HEAT DETECTOR

Respond to abnormally high temperature

FIXED TEMPERATURE DETECTOR

RATE CONDENSATION DETECTOR

RATE OF RISE DETECTOR

actuate when temperature reaches predetermined temp

Used where high ambient temperatures exist /sudden changes in temperature can occur

Types of design

Bimetallic sensing element

High expansion aluminum tube encase 2 insulation struts with opposing open contact points.

Operate when temp ↑at a rate exceeding predetermined amount (Threshold btwn 15 - 25 deg)

e.g. kitchens, boiler rooms etc.

Electric conductivity type

Fusible alloy type

Expansion struts and expansion shell have different coefficient of expansion

Sealed chamber with air contains diaphragm switch and small vent.

Heat sensitivity cable type

- Slow rate of temp ↑ - Rapid rate of temp ↑ - Expand > touch > Actuate - Contract > no touch > reset

Temp ↑, air expand, some escape out of vent. If air expand too quickly for excess air to escape, pressure will trigger the switch (balloon touch contact point), actuate alarm.

Liquid exppansion sensing element type

Flame detector
• • • Sensitive to infrared, visible or UV radiation produced by a fire designed to respond to a fire within the detector’s cone of vision typically within one second Flame detector applications – aircraft hanger, yard storage, chemical processes and flammableliquid storage

A. • •

Infrared Flame Detectors Contain photocell that is responsive to radiant energy at wavelengths below human vision range A light filter allows only a narrow band of infrared radiation, which is unique in a fire to reach the photocell. Ultraviolet Detectors • Contain a Geiger-Muller tube responsive to radiant energy in the 0.1- to 0.35 micron wavelength range The tube produces a pulse of current directly proportional to the level of uv light reaching the tube An alarm is initiated when the number of pulses per second is greater than the predetermined threshold

B.





Note: To reduce false alarms caused by non-fire sources, combination of UV/ infrared detectors are used. Flame...
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