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Unit 1 Introduction to Fire Safety
1. Introduction1.1 Importance of Fire Protection
How could a fire effect an organization?
NOTE: 40% of businesses hit by
fire never reopen!!
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. Introduction
1.5. NFPA Strategies
Residential properties– 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
2.2 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
2. Chemistry & Physics of Fire
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/tUnits: BTU/HR or J/sec.
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 Joules/sec
3.3.4. Heat Insulators
3. Heat Transfer
CONDUCTIONVS 2-3
Vertical Horizontal
Point-to-Point Transfer of Heat Energy from One Body to Another by a Heat-Conducting Medium
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 or Joules
hr. ft2 ºF sec.m2ºC
3.4.5. Newton‘s Law of Cooling
Formula: Icv = h AT
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
3. Heat Transfer
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.
4.2. 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. fuelb. oxidizing agentc. heat to produce free radicalsd. uninhibited free radical combination
4. Combustion
COMBUSTIONVS 2-7
Reducing Agent (Fuel)
Chemical Chain
Reaction
Oxidizing Agent
Heat
Chemical Chain
Reaction
Reducing Agent (Fuel)
Oxidizing Agent
Heat
The Fire Tetrahedron
PRODUCTS OF COMBUSTIONVS 2-23
Carbon Particles
Sulfur Dioxide
Water Vapor
Carbon Monoxide
Hydrogen Cyanide
Carbon Dioxide
Fuel
Oxygen Oxygen
4. SMOKE
3. FLAME
2. HEAT
1. LIGHT
Flammable Vapors
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%)
6.2. 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. Unique Combustion Phenomena
6.4. Flashover
6.5 Backdraft
6.6. BLEVE