Transcript Unit 1 Introduction to Fire Safety

Unit 1 Introduction to Fire Safety
1. Introduction
1.1 Importance of Fire Protection
How could a fire effect an organization?
NOTE: 40% of businesses hit by fire
never reopen!!
1. Introduction
1.2 The Overall Fire Picture – NFPA 2009

Every 22 seconds a fire department responds to a fire

1,451,500 fires reported in the US

3,320 deaths, 84% of which occur in residential homes

16,705 civilian injuries occurred as a result of fires

$15.4 billion in direct losses
1. Introduction
1.3 Where Fires Occur
49% were outside fires
34% were structural fires (78.2% residential)
17% were vehicle fires
1. Introduction
1.4 Causes of Residential Fires and Fire Deaths
Cooking
Heating
Arson
1. Introduction
1.5. NFPA Strategies

Residential properties
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–
–
–
–

Public Fire Safety Education
Smoke Detectors and Escape Plan
Residential Sprinkler Systems
Fire safe home products
Special fire safety needs for
high risk groups
Industrial properties
2. Chemistry & Physics of Fire
2.1 Nature of Heat
Heat – A quantity of thermal energy
- symbol is Q
Units of Heat: BTU or Calorie
Formula for heat: Q = MC∆T
2. Chemistry & Physics of Fire
2.2 Specific Heat – The amount of heat
required to raise one pound of a
substance by 1ºF
Units will be BTU/lb. ºF
2.Chemistry & Physics of Fire
2.3. Sensible Heat Change – the change in heat content
of a material due to a temperature change only, no
phase change.
2.4. Latent Heat Change – the change in heat content of
a substance when it undergoes a phase change only,
no temperature change.
2.5 Heat of vaporization - is a kind of latent heat
where liquid is converted to a gas (water fogs)
2.6 Heat of fusion - is a kind of latent heat where solid is
converted to a liquid
2. Chemistry & Physics of Fire
2.7
Sublimation – Under certain
circumstances some materials can
change from the solid to the vapor state
and visa versa, this usually occurs at
pressures below atmospheric.
2.8
Heat of Combustion is the amount of
heat released when something burns
Units are: BTU/LB
Joules/g
3. Heat Transfer
3.1. Basic Principle: Heat energy
always flows from hot to cold or
from higher energy state to lower.
Heat transfer implies a rate and the
symbol is “I”
I = Q/t
Units: BTU/HR or
J/sec.
3. Heat Transfer
3.2. Three major mechanisms of heat transfer
 Conduction
 Convection
 Radiation
3.3 Heat Conduction
3.3.1 Heat transfer caused by molecules
vibrating and colliding with other
molecules transferring their kinetic
energy
3. Heat Transfer
3.3.2. Factors that influence heat transfer via
conduction:
• Effects of distance upon heat transfer by conduction
• Effects of cross sectional area on heat transfer
• Effects of composition on heat transfer
k - Coefficient of thermal conductivity
units: BTU/hr ft ºF
3. Heat Transfer
3.3.3. Fourier’s Law of Heat Conduction
Icd = k A T
x
Units:
BTU/hr
or
3.3.4. Heat Insulators
Joules/sec
CONDUCTION
Vertical
Horizontal
Point-to-Point Transfer of Heat Energy from One Body to
Another by a Heat-Conducting Medium
VS 2-3
3. Heat Transfer
3.4. Heat Transfer by Convection
3.4.1 Heat transfer because of the movement
of a fluid (air) containing the heat
3.4.2. "Hot Air Rises"  Natural Convection
3.4.3. The rate of heat transfer via convection
is influenced by several factors
3. Heat Transfer
3.4.4. Convection Heat Transfer Coefficient
Symbol & Units (h)
BTU
hr. ft2 ºF
or Joules
sec.m2ºC
3.4.5. Newton‘s Law of Cooling
Formula: Icv = h AT
CONVECTION
Heat Transferred by
Movement of Heated Liquids or Gases
VS 2-4
3. Heat Transfer
3.5. Radiant Heat Transfer
3.5.1. Heat transfer via electromagnetic waves
3.5.2. Radiant heat transfer (emission) depends
on:
The nature of the surface (emissivity e)
The distance between the radiation source and the
object it strikes
RADIATION
Electromagnetic Waves Traveling Through Space Until They
Reach a Solid Object
VS 2-5
4. Combustion
4.1. Combustion: is a rapid oxidation
accompanied by the emission of heat & light
Oxidation - the chemical combination of an
atom or molecule with oxygen and the
chemical bonds contain energy.
4. Combustion
4.2. Key Principles of Combustion
4.2.1. Heat Energy necessary to initiate combustion
4.2.2. The reaction is self-sustaining once the ignition
source is provided
4.2.3. For combustion to occur you must have a:
a.
b.
c.
d.
fuel
oxidizing agent
heat to produce free radicals
uninhibited free radical combination
VS 2-7
COMBUSTION
The Fire Tetrahedron
Reducing
Oxidizing
Agent
Agent
(Fuel)
Chemical
Chain
Reaction
Heat
Oxidizing
Agent
Reducing
Agent
(Fuel)
Heat
Chemical
Chain
Reaction
PRODUCTS OF COMBUSTION
VS 2-23
Carbon Monoxide
Carbon Particles
4. SMOKE
Sulfur Dioxide
3. FLAME
Hydrogen Cyanide
2. HEAT
1. LIGHT
Water Vapor
Flammable
Vapors
Fuel
Carbon Dioxide
4. Combustion
4.3. Products of Combustion
4.3.1. Heat
4.3.2. Smoke
4. Combustion
4.3. Products of Combustion
4.3.3. Fire Gases
4.3.4. Light - Flaming
5. Rates of Combustion
5.1 Flammable Gas
5.2 Flammable Liquid
5.3 Flammable Solid
6.Unique Combustion Phenomena
6.1. Explosion- is the rapid
expansion of a gas that converts
the potential energy of the gas
to kinetic energy.
6.1.1. Sources of explosions in industry
– Fuels (50%)
– Flammable Liquid Vapors (12%)
– Trapped Steam (7%)
– Gas Leakage (6%)
– Rupture of Pressurized Equipment (6%)
6. Unique Combustion Phenomena
6.2. Deflagration- is the burning of a gas or
aerosol that is characterized by a
combustion wave
6.3. Detonation - the burning of a gas or
aerosol that is characterized by a shock
wave
6. Unique Combustion Phenomena
6.4. Flashover
6.5 Backdraft
6.6. BLEVE
FLASHOVER
VS 2-18
BACKDRAFT
• Low Oxygen
• High Heat
• Smoldering Fire
• High fuel vapor
concentrations
PRE-BACKDRAFT
• Introduction of oxygen causes fire of explosive force
BACKDRAFT
VS 2-22b