Fundamental Electronics

1. BASIC LOW VOLTAGE SYSTEMS
CHAPTER 15.3
Fire Sensors
By
Dinesh Kumar Sarda

2. What is Fire?
A process in which substances
combine chemically with oxygen
from the air and typically give
out bright light, heat, and
smoke; combustion or burning.

3. CAUSES OF FIRE
Kitchen Stoves
Faulty Wiring
Smoking
Lighting
Flammable Liquids
Candles
Home Heating
Children…. AND WE
ALSO CONTRIBUTE TO
FIRE HAZZARDS

4. TYPES OF FIRE
CLASS A
CLASS B
CLASS C
CLASS D
CLASS E
CLASS F
Not all fires are the same.
Different fuels create
different fires and require
different types of fire
extinguishing agents.
Fires are broadly classified
into 6 types

5. CLASS A FIRE
Class A fires are
fires in ordinary
combustibles
such as wood,
paper, cloth, trash,
and plastics…Etc.

6. CLASS B FIRE
Class B fires are
fires involving
flammable
liquids such
as gasoline,
petroleum oil
and paint…Etc.

7. CLASS C FIRE
Class C fires are fires
involving gases such
as Butane, Propane,
acetylene..Etc.

8. CLASS D FIRE
Class D fires are fires
involving combustible
metals such
as potassium,
sodium, aluminum,
magnesium.. Etc.

9. CLASS E FIRE
Class C fires are fires
involving energized
electical
equipment such
as motors,
transformers, and
other appliances.

10. CLASS F FIRE
Class F fires are
fires in cooking oils
and greases such
as animals
fats and vegetable
fats.
classes of fire.mp4

11. HOW TO EXTINGUISH FIRE??
For this we have to understand fire triangle

12.  Oxygen, heat, and fuel are frequently referred to as the
"fire triangle." Add in the fourth element, the chemical
reaction, and you actually have a fire "tetrahedron.“
 The important thing to remember is: take any of these
four things away, and you will not have a fire or the fire
will be extinguished.
 Essentially, fire extinguishers put out fire by taking away
one or more elements of the fire triangle/tetrahedron.
 Fire safety, at its most basic, is based upon the principle of
keeping fuel sources and ignition sources separate.

13. TYPES OF FIRE EXTINGUISHERS
Water and Foam TYPE:
Water and Foam fire extinguishers
extinguish the fire by taking away
the heat element of the fire triangle.
Foam agents also separate
the oxygen element from the other
elements.
Water extinguishers are for Class A fires
only.

14. CARBON DIOXIDE
Carbon Dioxide fire extinguishers
extinguish fire by taking away
the oxygen element of the fire triangle
and also be removing the heat with a
very cold discharge.
Carbon dioxide can be used on Class B
& C fires. They are usually ineffective
on Class A fires

15. DRY CHEMICAL
Dry Chemical fire extinguishers
extinguish the fire primarily by
interrupting the chemical reaction of
the fire triangle.
Today's most widely used type of fire
extinguisher is the multipurpose dry
chemical that is effective on Class A, B,
and C fires. This agent also works by
creating a barrier between
the oxygen element and the
fuel element on Class A fires.
Ordinary dry chemical is for Class B & C
fires only.

16. WET CHEMICAL
Wet Chemical is a new agent that
extinguishes the fire by removing the
heat of the fire triangle and prevents re-
ignition by creating a barrier between
the oxygen and fuel elements.

17. CLEAN AGENT
Halogenated or Clean
Agent extinguishers include the halon
agents as well as the newer and less
ozone depleting halocarbon agents. They
extinguish the fire by interrupting
the chemical reaction of the fire triangle.
Clean agent extinguishers are primarily
for Class B & C fires. Some larger clean
agent extinguishers can be used on Class
A, B, and C fires

18. Dry Powder
Dry Powder extinguishers are similar to dry
chemical except that they extinguish the
fire by separating the fuel from
the oxygen element or by removing
the heat element of the fire triangle.
However, dry powder extinguishers are for
Class D or combustible metal fires, only.
They are ineffective on all other classes of
fires.

19. WATER MIST
Water Mist extinguishers are a recent
development that extinguish the fire by
taking away the heat element of the fire
triangle. They are an alternative to the clean
agent extinguishers where contamination is
a concern.
Water mist extinguishers are primarily for
Class A fires, although they are safe for use
on Class C fires as well.

20. Cartridge Operated Dry Chemical
Cartridge Operated Dry Chemical fire
extinguishers extinguish the fire primarily
by interrupting the chemical reaction of
the fire triangle.
Like the stored pressure dry chemical
extinguishers, the multipurpose dry
chemical is effective on Class A, B, and C
fires. This agent also works by creating a
barrier between the oxygen element and
the fuel element on Class A fires.
Ordinary dry chemical is for Class B & C
fires only.

21. NOTE….
It is important to use the correct
extinguisher for the SPECIFIC
type of fuel! Using the incorrect
agent can allow the fire to
re-ignite after apparently being
extinguished successfully.

22. WHAT CAN BE DONE TO AVOID FIRE ITSELF
USE FIRE SENSORS

23. WHAT IS A FIRE SENSOR ??
A flame detector is a sensor designed to
detect and respond to the presence of a flame
or fire.
Responses to a detected flame depend on the
installation, but can include sounding an
alarm, deactivating a fuel line (such as a
propane or a natural gas line), and activating
a fire suppression system.

24. BASIC WORKING…
Make a Fire Alarm at Home - Science Project
(Hindi - Urdu).mp4

25. Intro to Basic Fire Alarm Technology

26. Let’s examine the
components that
make a basic Fire
Alarm Control
System.

27. Main Controller
• The brains of the
system
• Provides power to the
system, monitors inputs
and controls outputs
through various circuits
• Performs other
functions as required
by the appropriate code

28. Primary (AC)
Secondary (DC)
Requires two Power Sources
Elements of a Control Panel

29. Inputs
• Initiating Device: A system component that
originates transmission of a change of state
condition, such as a smoke detector, manual
fire alarm box, supervisory switch, etc...
• Initiating Device Circuit (IDC): A circuit to
which automatic or manual initiating devices
are connected

30. Smoke Detector
Manual Pull Station
A fire alarm
system can have
a variety of
input devices.
Inputs
Elements of a Control Panel

31. Outputs
• Notification Appliance: A fire alarm system
component such as a bell, horn, speaker, light,
or text display that provides audible, tactile, or
visible output, or any combination there of.
• Notification Appliance Circuit: A circuit or
path directly connected to a notification
appliance.

32. Elements of a Control Panel
Horns
Strobes
Outputs

33. The Basic System
Secondary (DC)
Primary (AC)
Outputs
Inputs
Main Controller

34. The Stages of a Fire
Stage One
Incipient: Products of Combustion particles are
produced (<0.3 microns). No visible smoke or
detectable heat. May occur for milliseconds or
days.
REMEDY: Use ionization detectors

35.  Stage Two :
Smoldering: Visible smoke particles are produced
(>0.3 microns). Little visible flame or noticeable
heat.
REMEDY: Use Photoelectric Detectors

36. Stage Three
Flame: Rapid combustion produces radiant energy
in the visible, and invisible (IR, UV) spectrums.
Heat begins to buildup at this stage.
REMEDY: Use Spark or Flame Detectors

37. Stage Four
– High Heat: Uncontrolled combustion is caused by the
heating of nearby combustibles to their ignition point.
• Use Heat Detectors
– Note! Major disadvantages of using thermal energy
for fire identification are
• Takes a while for a fire to be recognized
• The toxic gases that are produced before an alarm point is
reached

38. Types of Detectors
Photoelectric
Light Scattering
Light Obscuration
Ionization
Duct
Heat (Thermal)

39. Photoelectric Smoke Detectors:
Light-Scattering Type
• Uses a Light-Emitting Diode (LED) that sends a beam
of light into a dark chamber- a photo diode sits on
the other side of a partition within the chamber
• Smoke particles entering the chamber deflect some
of the light rays into the photo cell. The photo cell
generates a current when exposed to light, and if the
current reaches a certain level, the detector alarms.

40. Photoelectric Smoke Detectors:
Light Obscuration Type
• In a projected Beam
Detector, alarms are
generated by diffusing
the projected light beam
by a specified
percentage of
obscuration.
• Total beam blockage
generally results in a
trouble signal.

41. Ionization Smoke Detectors
• Contain a small amount of radioactive
material encapsulated in a metal chamber.
Ionizing radiation develops a low, but steady
electrical current. Smoke particles entering
the chamber disrupt the current and trigger
the detector's alarm.
• Ion detectors react more quickly to fast
flaming fires that give off little smoke.

42. Heat Detectors
• Fixed Detectors:
– Alarm when the sensing element reaches a certain set point.
– Two common models have 135 and 200-degrees F range.
– Fixed element is generally a non-restorable type, and when
activated, must be replaced.
• Rate-of-Rise Detectors:
– Respond when the rate of temperature increase is greater
than an allowable limit (15 degrees in 60 secs.) (placement in a
stable environment) (e.g.. ovens, heating vents, etc.).
– The Rate-of-Rise element is restorable when conditions return
to normal.
• Rate Compensation will respond regardless of the rate
of temperature rise.

43. Duct Detectors
• Photoelectric detector
mounted in housing
outside the ductwork
that has probes that
extend into the duct to
sample the air inside the
duct.
• Primarily used as a
smoke control device to
control the flow of air in
ductwork.

44. Initiating Devices
Manual Fire Alarm Stations
• Manually-operated
device used to initiate an
alarm signal
– Single Action Stations
require a single operation
to activate it. Generally a
pulling down action.
– Dual Action Stations
require two distinct
operations. A set-up and
an activating action.

45. PRACTICAL EXAMPLE
Stat-X Fire Suppression System - Animation
Video.mp4