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

1.4 Causes of Residential Fires and Fire Deaths

Cooking

Heating

Arson

1. Introduction1.5. 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

CONDUCTION VS 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

CONVECTION VS 2-4

Heat Transferred byMovement of Heated Liquids or Gases

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

RADIATION VS 2-5

Electromagnetic Waves Traveling Through Space Until They Reach a Solid Object

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 Combustion4.2.1. 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. SMOKE3. FLAME2. HEAT1. LIGHTFlammable

Vapors

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

4. Combustion

5. Rates of Combustion5.1 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

FLASHOVER VS 2-18

BACKDRAFT VS 2-22b

• Low Oxygen• High Heat• Smoldering

Fire• High fuel vapor concentrations

• Introduction of oxygen causes fire of explosive force

PRE-BACKDRAFT

BACKDRAFT