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FIRE SAFETY

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by

Terry Curtis

on 27 November 2013

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Transcript of FIRE SAFETY

LO1 Fire Science
FIRE SAFETY
in BUILDINGS

The Fire Tetrahedron (A pyramid)

For many years the concept of fire was symbolized by the Triangle of FIRE and represented, fuel, heat, and oxygen.
Fire research has since determined that a fourth element, a chemical chain reaction, was a necessary component of fire.
The fire triangle was changed to a fire tetrahedron to reflect this fourth element. A tetrahedron can be described as a
pyramid which is a solid having four plane faces. Essentially all four elements must be present for fire to occur, fuel,
heat, oxygen, and a chemical chain reaction. Removal of any one of these essential elements will result in the fire being extinguished.

Outcome 1

Explain fire safety theory and prevention measures.

Knowledge and / or skills
♦ Fire science
♦ Fire safety design
♦ Prevention measures

Evidence Requirements
Candidates will need evidence to demonstrate their
knowledge and / or skills by showing that they can:
explain the factors and principles in the establishment and development of fires
♦ describe fire safety design strategies
♦ identify fire prevention measures

LO1: Fire Safety Design:

Design objectives — life safety and property protection

Tactics — prevention, communication, escape, extinguishment, containment

Traditional and fire engineering approaches

LO1: Fire Safety Design - Design objectives

LO1: FIRE SCIENCE - Fire growth curve

Flashover and Backdrafts

Although ISO 13943 defines flashover as "transition to a state of total surface involvement in a fire of combustible materials within an enclosure," a broad definition that embraces several different scenarios, including backdrafts, there is nevertheless considerable disagreement regarding whether or not backdrafts should properly be considered flashovers.
The most common use of the term flashover is to describe the near-simultaneous ignition of material caused by heat reaching the autoignition temperature of the combustible material and gases in an enclosure; flashovers of this type are not backdrafts as they are triggered by thermal change.
Backdrafts, on the other hand, are caused by the introduction of oxygen into an enclosure that may already be hot enough for ignition; thus, backdrafts are triggered by chemical change.

One man already charged with murder and further two still in custody following fire that killed woman and three children

Leyland school fire: Five boys held on suspicion of arson
Unit title: Fire Safety in Buildings
Unit code: DW4X 35

Unit purpose:

This Unit seeks to provide the candidate with knowledge of the principles of combustion and the key stages in ignition, fire growth, development and decay of fire in buildings. It will also provide the candidate with the knowledge of the measures taken to contain fire and the provision made to allow building occupants to escape the effects of a fire.
Skills will also be developed to allow candidates to be able to assess a building for compliance with fire safety legislation.

On completion of the Unit the candidate should be able to:

1 Explain fire safety theory and prevention measures.
2 Describe passive and active measures of fire containment.
3 Describe means of escape provision in buildings.
4 Appraise development proposals for compliance with current legislation
Abrasion
growth - decay of a fire
Flashover is the sudden transition to fully developed fire. This phenomenon involves a rapid transition to a state of total surface involvement of all combustible material within the compartment….Flashover may occur as the fire develops in a compartment or additional air is provided to a ventilation-controlled fire (that has insufficient fuel in the gas phase and / or temperature to backdraft).
Flashover is the point at which temperatures get so hot that everything in the room bursts into flames. The incorporation of flame retardants increases the time to flashover, by some estimates up to 8 minutes.











Progression of a fire without flame retardants (red) and with flame retardants (blue).








While that may not seem like a lot of time, in a fire every second counts, and those extra minutes might be the difference between life and death. In fact after the August 2nd, 2005 plane crash at Toronto’s Pearson Airport, where an AirFrance airbus carrying 309 passengers, burst into flames, yet everyone managed to escape, flame retardants were credited with giving the flight crew the few extra minutes needed to ensure everyone got off the plane safely.

Toaster
Chip Pan Fires
Smoking
Naked flame +
fuel source
Electrical overload
Offices
Houses
Terrace
Flats
Semi - detached dwellings
Who responds?
Lightning strikes
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Electrical switchgear
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SOURCES of IGNITION
Causes of fires
Fire POINT:
The fire point of a fuel is the temperature at which it will continue to burn for at least 5 seconds after ignition by an open flame. At the flash point, a lower temperature, a substance will ignite briefly, but vapor might not be produced at a rate to sustain the fire.
Most tables of material properties will only list material flash points, but in general the fire points can be assumed to be about 10 °C higher than the flash points. However, this is no substitute for testing if the fire point is safety critical.
FLASH POINT
:
Temperature at and above which a liquid gives off enough flammable vapour to form a mixture with air that can be ignited by contact with a hot surface, spark, or flame.
the Lower the flash point, greater the fire hazard.
spontaneous ignition:
Spontaneous combustion or spontaneous ignition is a type of combustion which occurs by self heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high temperatures) and finally, ignition.
Development of a Fire:

A fire develops typically in four stages, and fire detectors are designed to detect some characteristic effect of one or more of these stages:

Incipient stage.
No visible smoke, no flame and very little heat. A significant amount of invisible (but sometimes smellable) combustion particles may be created. This stage usually develops slowly.

Smouldering stage.
Smoke, but no flame and little heat.

Flame stage.
Visible flame, more heat, often less or no smoke, particularly with flammable liquids and gas fires.

Heat stage.
Large amounts of heat, flame, smoke and toxic gases are produced.
The transition from the previous stage can be very fast
triangle of fire
Convection: The transfer of heat by circulation or movement through liquid or gases.

Radiation: Radiation is the transfer of heat from an object traveling through a space
until absorbed by another object.


Conduction:
Conduction is the transfer of heat from a solid to another solid touching each other
.

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