building fire protection and security lesson 1

8/2/2019 Building Fire Protection and Security Lesson 1

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Fire and smoke dynamics, principles and characteristics Unit 1

Factors and Principles in the

Establishment and Development of Fire


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Lecturer Jason Farrell

Profession Civil Engineer Specializing in

Multi-storey Buildings and Interior Fit Out

Contact Information

Cell No. : 321 1227 Email : [email protected]


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Factors and Principles in theEstablishment and Development

of Fire


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Fire losses can be one of the greatest threats

to an industrial organization in terms of

loss of life

financial losses

loss of property and property damage


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Not only do they have to ensure that the

property is adequately protected to prevent

catastrophic financial losses to the organization,

but there is also the moral obligation to protect

the workers and members of the community

from the devastating effects that a fire can have

upon the entire community.


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The adverse financial effects can be felt by an

organization long after the fire is

extinguished.


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Financial losses to an organization due to fire:

Loss of assets (buildings, equipment etc)

Loss of revenue (sales and production)

Loss of earnings due to downtime

Loss of share value/investor confidence

Cost of cleanup/reconstruction

Costs attributed to loss of life/injury and damage to third parties

Etc.


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Fire protection and prevention involves

Recognizing situations that may result in an

unwanted fire,

evaluating the potential for an unwanted event, and

developing control measures that can be used to

eliminate or reduce fire risks to an acceptable level.


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Fire safety engineering achieves this by

evaluating buildings to determine fire risks,

designing fire-detection-and suppression

systems, and

researching materials and consumer products


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In order to prevent fires from occurring and to

extinguish them successfully anunderstanding of the chemical and physical

characteristics of fire is important.


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The chemistry of fire involves the ways in

which fires can be started and sustained at

the molecular level of the fuel source.

The physical aspects of fire involve itsthermal properties, methods of heat transfer,

and method of extinguishment.


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Because fire is a chemical reaction, it is

important to understand not only which

hazardous materials pose fire hazards in theworkplace but also the by-products of the

combustion process.

By-products of fire can often be morehazardous than the hazardous material

involved in the fire.


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Fire is the result of a chemical reaction

between oxygen (or an oxidizing agent) inthe atmosphere and fuel which has been

sufficiently heated to achieve its ignition

temperature.


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There are four elements essential to initiate

and sustain fire: Oxygen

Fuel

Ignition source or energy source

Chemical chain reaction


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Oxygen Air is the most common source of oxygen with, on

average, 21 percent of air being oxygen.

Sources of oxygen can also include oxidizers.

Oxidizers are substances that acquire electrons from afuel in a chemical reaction and release oxygen during

combustion. Examples of common oxidizers include elements of

fluorine, chlorine, hydrogen peroxide, nitric acid,sulphuric acid, and hydrofluoric acid.


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Fuel

Most fires involve a fuel that contains carbon

and hydrogen, such as wood, paper, orflammable and combustible liquids and gases

Other potential fuel sources are combustible

metals, such as aluminium or magnesium.


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For fire-extinguishment purposes, the fuels are classifiedas follows:

Class A: carbon-based products such as wood and paper

Class B: flammable gases and liquids

Class C: combustible materials where electricity may be present

Class D: combustible metals, such as aluminium, magnesium,

titanium, and zirconium

Class K: liquid cooking media (Lard, cooking oil etc.)


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Each fuel classification also has a unique

symbol.

Fire extinguishers are an example of a piece

of equipment that uses these fuel-classification symbols.


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Ignition source or energy source

The source of energy that heats the material

to its ignition is the ignition source or energysource.

Some examples of ignition sources for fires in

industrial occupancies include excessiveelectrical current, heating equipment, flames

and sparks, and lightning.


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Ignitiontemperature:

The minimum temperature of a material required to

initiate or cause self-sustained combustion of thematerial.

Some examples of ignition temperatures of commonbuilding materials include

plywood (3900

C), gypsum board (5650C), carpet (4120C) asphalt shingles (3780C)


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Ignition temperature can vary

Oxygen in the air is the main influencing factor:

the richer the oxygen levels, the lower the

ignition temperature.

The rate of heat rise, the duration of heating,

and the size and shape of material also influence

ignition material.


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It should also be noted that spontaneous

ignition can occur when the ignition source is

slow oxidation with very limited heat lossthat produces a temperature rise above the

ignition temperature of the material.

An example of spontaneous ignition inindustrial occupancies are oil-soaked rags

stored in 55-gal. waste drums.


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ChemicalChain Reaction Fire is self-perpetuating.

The chemical chain reaction occurs within thematerial itself when the fuel is broken down byheat, producing chemically reactive freeradicals, which then combine with the oxidizer.

Once a fire is started, the heat from the flamekeeps the fuel at the ignition temperature.Assuch it continues to burn as long as there is fueland oxygen around it


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The flame heats any surrounding fuel so it

releases gases as well.

When the flame ignites the gases, the fire

spreads.


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Fire cannot exist without all of these

elements in place and in the right

proportions.

Fire can be extinguished by removing any oneof the elements of the fire tetrahedron.


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To truly understand combustion, we mustalso understand oxidation.

Oxidation can be defined as the chemicalcombination of any substance with anoxidizer.

With combustion, the energy thataccompanies oxidation is commonly given offas heat and light.


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It is important to note that solids do notcombust but rather gases released from the

solid due to the application of heat.

The heat provided during combustionprovides the necessary energy for atoms in

one gaseous compound to break their bondswith each other and recombine with availableoxygen atoms in the air to form newcompounds plus more heat.


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Only some compounds will readily break

apart and recombine in this way, the various

atoms have to be attracted to each other inthe right manner.

For example, when you boil water, it takes

the gaseous form ofsteam, but this gasdoesn't react with oxygen in the air


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There are four major products of combustion:heat, smoke, light, and fire gases.

These products of combustion are critical for firepurposes not only in terms of extinguishmentbut also in terms of life safety and buildingdesign.

The primary loss of life in a fire is due to the toxicfire gases. (carbon monoxide, carbon dioxide)


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The rates of combustion of gases, liquids, and

solids vary depending on several factors.

Chemical composition of the fuel The state of matter of the fuel (solid, liquid, gas)

The piloted ignition temperature and the un-piloted ignition temperature

Fuel heat production

Concentration of oxygen/oxidizing agents present


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The chemical composition of a material will determine

how combustible it is

It is also an important factor in determining how much

heat output will be produced by combustible materials

and how quickly a fire will grow and spread

Materials composed of carbon and hydrogen are the most

flammable

These include organic materials as well as hydrocarbons


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The state of matter of a fuel can affect how

readily it ignites and affect the rate of heat

production

The rates of combustion of gases, liquids, andsolids vary depending on several factors


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For solids: The rate of combustion varies primarily based on the size

of the solid particles

Smaller particles having a higher rate of combustion

Fuel's shape also affects burning speed.Thin pieces of fuelburn more quickly than larger pieces because a largerproportion of their mass is exposed to oxygen at any

moment.

The moisture content and continuity of the solid particlesalso play an important role in the growth anddevelopment of fire


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For Liquids

The physical state of the liquid - whether the

combustion occurs in a still pool, flowingcurrent, or spray or foam

Vapour pressure The pressure at which the

liquid begins to evaporate


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For flammable gases, the rate of combustion

varies based on the extent to which the gas

mixes with air prior to combustion and on thedegree of motion and turbulence of the

gases.

The ignitability of a flammable gas is affected

by how closely the molecules of the gas are incomparison to surrounding air molecules


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Different flammable fuels catch fire at

different temperatures

It takes a certain amount of heat energy to

change any particular material into a gas, andeven more heat energy to trigger the reaction

with oxygen.


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The necessary heat level varies depending onthe nature of the molecules that make up thefuel.

A fuel's piloted ignition temperature is the heatlevel required to form a gas that will ignite whenexposed to a spark.

At the unpiloted ignition temperature, which ismuch higher, the fuel ignites without a spark.


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Fuel's heat production depends on how muchenergy the gases release in the combustionreaction and how quickly the fuel burns.

Both factors largely depend on the fuel'scomposition.

Some compounds react with oxygen in such away that there is a lot of "extra heat energy" leftover. Others emit a smaller amount of energy.


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Similarly, the fuel's reaction with oxygen may

happen very quickly, or it may happen more

slowly.

Presence of a fire suppression agent (forexample, water) may extract heat from a heat

from a fire and limit further production


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As was mentioned previously the oxygen present inthe combustion affects the rate of fire growth anddevelopment

Too little oxygen will stifle fire development

Too much oxygen can prevent ignitable moleculefrom coming into contact with one another


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There are numerous heat sources in the work environmentcapable of starting a fire or keeping it burning once it isstarted.

The following is a description of heat sources.1. Chemical heat.Heat of combustion is the heat that is

released during a substances complete oxidation. Calorificvalues of fuel are expressed in joules per gram of material.

2. Spontaneous heating.Spontaneous heating is the processby which a material increases temperature withoutdrawing heat from its surroundings. If allowed to heat tocombustion temperatures, spontaneous ignition can takeplace.


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3. Heatofdecomposition.Heat of decomposition is theheat released by the decomposition of compounds thathave been formed.Acetylene is an example of a productthat, once it starts to decompose, generates heat.

4. Heatofsolution.This is heat released when a substanceis dissolved in a solution.

5. Electrical heat.Also called resistance heating, this is

heat generated due to the resistance electricityencounters when traveling through a conductor.

6. Arcing.Arcing occurs when electrical energy jumpsacross a gap in the circuit carrying the electrical energy.


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7. Sparking.This takes place when a voltage discharge is toohigh for a low-energy output.

8. Staticelectricalcharge.This is an electrical charge that

accumulates on the surfaces of two materials that havebeen brought together, then separated.

9. Lightning.This is the discharge of an electrical charge froma cloud to an opposite charge (i.e., another cloud or theground).

10. Mechanical heat.This is the mechanical energy used toovercome the resistance to motion when two solids arerubbed together; it is also known as frictional heat.

11. Nuclearheat.This is heat energy released from the

nucleus of an atom.


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Materials and processes commonly found in the industrialworkplace pose unique fire hazards.

Fire risk is minimized by controlling potential fuel and

oxidizer sources and proper handling and storage ofignitable materials

Work procedures involving housekeeping and the controlof ignition sources should also be taken into account as an

integral part of the fire-protection program. Industrial fire prevention must address the specific

processes and hazards associated with each activity


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The most common cause for fire in a facilityresult from electrical failures

These include short circuits, ground faults, orother electrical failures.

Each year, thirty thousand fires are recorded in

the United States, and investigations have foundthat many of those were initiated from electricalsources (Jones and Jones 2000, 15)


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Examples of sources of electrical fires in theworkplace include the following:

Misuse of chords Poor Maintenance

Ground Failure

Damaged insulation

Sparking Circuit Overload Short Circuit

Arching


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FLAMMABLE LIQUIDS ANDCOMBUSTIBLE LIQUIDS

Flammable and combustible liquids pose a unique hazard in

the workplace primarily because of the amount of fuel theycan provide for a fire and the relatively low heat sourcenecessary to ignite the material.

Flammable and combustible liquids are classified as eitherflammable or combustible based upon their flash point.


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Flammable liquids are any liquids having a flash pointbelow 1000F

Flammable liquids are known as Class I liquids. Class Iliquids are divided into three classes as follows :

1. Class IA shall include liquids having flash points below73F and having a boiling point below 100F.

2. Class IB shall include liquids having flash points below73F and having a boiling point at or above 100F.

3. Class ICshall include liquids having flash points at orabove 73F and below 100F.


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Combustible liquids typically will require

some external heating to produce a sufficient

concentration of vapours

Combustible liquids are any liquid having aflash point at or above 100F and are divided

into two classes.


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Two Classes of Combustible Liquids:

Class II liquids include those liquids with flashpoints at or above 100F and below 140F

Class III liquids include those liquids with flashpoints at or above 140F.


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Hydrogen is a nontoxic, colorless gas with no

odor.

It is flammable and may form mixtures with

air that are flammable or explosive.

Hydrogen may react violently if combinedwith oxidizers, such as air, oxygen, and

halogens.


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Hydrogen can be found in a variety of industriesserving a number of useful purposes.

It can be stored in containers such as cylinders orit may be part of a tank, piping, and manifoldsystem.

Hydrogen can be used in a gaseous form or

stored under pressure in a liquefied form.

Regardless of the state it is stored in, hydrogenposes an extreme fire hazard


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Acetylene consists of 92.3 percent by weight

of carbon and 7.7 percent by weight of

hydrogen

Acetylene is most often associated with itsuse as a fuel in welding and cutting

operations


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Oxygen is a non-flammable gas, meaning

that it does not burn

Introducing pure oxygen to greases and oils

can result in spontaneous combustion

equipment making up a bulk oxygen systemshould be cleaned in order to remove oil,

grease, or other readily oxidizable materials


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Ammonium nitrate can be in the form ofcrystals, flakes, grains, or prills, includingfertilizer grade, dynamite grade, nitrous-oxide

grade, technical grade, and other mixturescontaining 60 percent or more ammoniumnitrate

ammonium nitrate in the workplace poses ahazard it poses as an oxidizing agent and anexplosion hazard


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Fire protection begins during the preplanning

phase of any new building design or

remodelling.

Construction can affect fire and smokespread, life safety, and the extent of fire

damage that will occur within the building


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Fire in buildings adds to the fire problem for thefollowing reasons

1.T

he building itself may burn.2. The contents of the building may be ignited.3. Occupants of the building may be trapped by the fire.4. The building structure may make it difficult to attack the

fire.

5. The building may collapse in whole or part during thefire.

6. The fire may extend beyond the original point of originto other buildings.

7. Firefighters may be injured or killed.


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Buildings are constructed of a variety of building materials, each of which influenceshow that building will be affected during afire situation

All materials can be damaged by fire even if

they do not burn because all structuralmaterials used in building construction areadversely affected by the elevatedtemperatures caused by a fire


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Steel

In commercial construction, steel is the most

common material used

Steel is non-combustible and does notcontribute fuel to a fire.

Structural steel does have three characteristicsthat affect its performance when exposed to afire.


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SteelContd

Characteristics of steel affected by Fire

1. Steel conducts heat, thereby aiding heat transfer2. The high coefficient of expansion of steel causes

it to expand when heated causing stress on themembers

3. steel will lose its strength when subjected tohigh temperatures


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Wood

Wood is combustible, and as it burns, it loses itsstructural integrity

Fire-retardant treatments may delay ignition andretard combustion when applied to wood

A common fire-retardant treatment of wood is toimpregnate the wood with mineral salts

This treatment will reduce the woods flame spread,but the wood is still combustible.


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Masonry and Brick

Masonry and brick products are quite fire

resistant, but they can spall when subjected toelevated temperatures from a fire

Spalling is a loss of the surface of the brick andother masonry products

Hollow concrete blocks also generally retaintheir structural integrity when exposed to a firebut can crack at elevated temperatures


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ReinforcedConcrete As a general rule, reinforced concrete is very fire

resistant

The type of aggregate used in this reinforcedconcrete, its moisture content, and the fire loadingwill determine the members fire resistance

When exposed to a fire, however, the concrete andsteel bond can fail, which can result in failures of thereinforced member, as well as spalling and some lossof strength


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Gypsum Gypsum products include such products as

plasterboard and plaster, both of which haveoverall excellent fire-resistive properties

These properties exist because gypsum has a

high portion of chemically combined water,and when it is exposed to a fire, theevaporation of this water requires a greatdeal of heat energy


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The NFPA has developed a classification

system for building types.

All buildings and structures shall be classified

according to their type of construction


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Building Types

TypeIbuildings commonly called fire resistive,

have structural members such as the frame,walls, floors, and roof that are all non-combustible with a minimum specified fire-resistive rating.

In general, theseType I buildings will withstandfire for several hours without structural failure.


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TypeIIis a construction type in which the structuralelements are made entirely of noncombustible orlimited-combustible materials, hence the common

name noncombustible.

Although the building materials are noncombustible,they do not have a sufficient fire-resistance rating tobe classified as fire resistant.

When exposed to a fire, the structure will not burn orcontribute fuel to a fire involving contents, but it cancollapse due to structural steel failure.


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TypeIII, which is commonly called ordinaryconstruction, is a construction type where theexterior walls are noncombustible with aminimum two-hour fire resistance, but theinterior is constructed of combustiblematerials.

The interior construction is typically made ofwood joist and studs; therefore, the entireinterior is easily destroyed by fire


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TypeIVis a construction type in which

structuralmembers are basicallyof

unprotected wood with large cross-sectionalareas, hence the common name of plank,

timber, or mill construction.

Bearing walls, bearing portions of walls, andexterior walls must be noncombustible and

have at least a two-hour rating


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TypeVconstruction is a construction type

where exterior walls andstructural members

are primarily made of wood or othercombustible materials.

Type V construction provides the lowest

degree of fire protection

building fire protection and security lesson 1

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