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Unit 36 - Forensic Fire Investigation Assignment 2 (Distinction)
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Assignment 2 – Fire InvestigationDistinction
Scientific Conclusions in Relation to the Fire at Harrow Court.
Below will be scientific conclusions which have been drawn from the evidence which was present at the
Harrow Court fire.
Evidence at the seat of the fire –
Establishing the area of where the fire started is what essential allows how the fire started to be determined.
The area in which a fire started is known as the seat of the fire and this is where the area of severest burning
occurs, in relation to the Harrow Court fire the most severest burnt area was around the television, as around
the tv there was a lot of damage as well as a large amount of charcoal and significant burn patterns present
around the tv itself. Also, there was circular burn patterns present on the ceiling, these were found vertically to
the fires origin. Although, Mr Savage stated that the tea light candles him and Ms Close placed on the tv are
what caught on fire due to the fact when he woke, he observed smoke coming from the television, the
possibility of arson can’t simply be ruled out, therefore, an investigation had to be conducted to establish
exactly how the fire was caused. Through an investigation, it was able to be clarified that this fire wasn’t a case
of arson. Arson is deemed as a crime of intentionally and maliciously, or recklessly starting a fire. The reason
for this is because there was no evidence of smashed windows or doors, this means that nobody forced entry
into the flat besides the firefighters which had to force entry into the flat through the front door in an attempt
to tackle to fire and rescue the occupants, however, if the firefighters didn’t open the door when they did the
damage probably wouldn’t be as to an extent in which it was, as a flashover wouldn’t have happened. Arson
can also be ruled out further due to the fact that there was no multiple burn pattern present, the reason as to
why multiple burn patterns indicate a sign of arson is because when an intentional fire is lit the arsonist will
tend to light multiple areas on fire in hope that it will burn, not realising that it leaves multiple burn patterns,
as a fire started normally and leaving multiple burn patterns in various areas would be extremely uncommon
as it would mean multiple things had to catch on fire, which in reality, is impossible. Also, the fact that there is
circular burn patterns directly above the origin indicates it’s not a case of arson is due to the fact that as heat
rises the fire will always burn upwards, hence, the burn pattern on the ceiling. Furthermore, there was no
volatile organic compounds e.g. gasoline, kerosene, etc present within Harrow Court which could have been
deemed as the possible ignition source of the fire, therefore, arson was able to be ruled out in regard to this
because when volatile vapours burn above a combustible or flammable liquid-accelerant pool, they will leave
behind distinct burn/ damage patterns which are different from other combustible products.
In an attempt to establish what the most possible sources of ignitions were in relation to this fire,
Hertfordshire Fire and Rescue Service (HFRS) decided to reconstruct the fire in a controlled environment in an
attempt not only back up their findings but also to identify what failing were possibly responsible for the fire.
Below are the conclusions which they came to:
Possible Sources of Ignitions Likelihood of it being the source
The use of tea light (double wicking.) PROBABLE
The use of tea light (flaring tea light.) POSSIBLE
The use of tea light (directly burning.) POSSIBLE
Deliberate ignition. POSSIBLE
The carless disposal of matches. POSSIBLE
Discared smoking materials carelessly POSSIBLE
(cigarettes.)
The use of other candles. ELIMINATED
An electrical fault. ELIMINATED
Gas installation or a malfunction of an ELIMINATED
appliance.
Malfunction of a heating appliance. ELIMINATED.
Natural occurances. ELIMINATED.
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, Assignment 2 – Fire Investigation
From carrying this out the HFRS concluded that e source of ignition was likely to be one of the two tea light
candles which were used and lit before being placed directly onto the surface of a portable plastic cased
television. A single wick tea light candle has a base temperature of around 80◦C, however, one of the candles
appears to have abnormally burnt. Although rare it can take place through the introduction of a foreign body
e.g. moth, match, etc behaving as a second wick. Figure 1 shows an image of the tea light candle, alight on a
portable plastic cased television surface. When a second wick is involved, the heat from both the first and
second wick can melt and subsequentelly ignite all the wax within the casing of the tea light. The heat from the
involvement of full wax would be transferred to the tea light aluminium casing conducting temperatures
around the 250◦C region. This heat is essentially sufficient enough to start the plastic casing of a television set
to decompse. Figure 2 shows an image of the tea light candle where the casing has now caught alight due to
the double wick and has started to decompose the television
casing.
Figure 2
Figure 1
A
reconstruction under conditions which were
controlled was carried out by the BRE (Building Research Establishment) along with various tests conducted by
the HFRS to essentially recreate the scenario which is stated as below. When recreating the event they
established that the recreated events all followed a rather similar pattern to the scenario described as below:
Essentially, through the information and statements available it was concluded that the most probable cause
of the fire is that the two tea light candles which were lit before being place directly on top of the television
within the main bedroom, on 1st February 2005 at around 23.10hrs by Mr Savage. The candles weren’t
extinguished before the occupants of the flat (Mr Savage & Ms Close) fell to sleep in the room. However, one
of the candles appears to have abnormally burnt causing it to heat up the Figure 3
televisions plastic casing. The abnormal burning would’ve sufficiently
generated enough heat to soften the plastic television casing before melting
it. As the tea light dropped through the television casing the flame ignited
the causing along with the flaming tea light wax, then the burning droplets
of plastic casing ignited the combustible internal components of the
television set, such as the electrical cables within the television, electrical
cables are capable of working at temperatures between -50◦C to +180◦C
these values are in relation to the most popular range of high temperature
cables which are silicone single and multicores, as this temperature was
exceeded before reaching the cables it’s likely that when the flames came
into contact with the cables it caused them to ignite as their ignition
temperature had been exceeded. . Figure 3 shows the television casing after
it had been ignited by the tea light.
BRE assisted the HFRS in carrying out the following tests; the reconstruction of bedroom and hallway for a
measured test burn, an investigation on the air flows through Harrow Court (including the two staircases
automatic opening vents influence), and fire modelling through using Computational Fluid Dynamics (CFDs.) In
regard to the reconstruction of the bedroom and hallway some concerns were highlighted such as; it would be
rather problematic if on the day of the tests the proposed event sequence didn’t produce the results which
were expected. Due to this reason the HFRS Fire Investigation Team conducted a series of tests in an attempt
to determine if the proposed event sequence was one which could’ve led to the complete involvement of the
bedroom, these tests were carried out on the 30 th August 2005 and it was established that the proposed
events could actually lead to the full involvement of the bedroom. The reconstruction of the hallway and
bedroom was carried out by BRE on the 13 th October 2005. Also, on the 20th December 2005 air movement
tests were carried out at Harrow Court. During the time this test was carried out the weather and temperature
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, Assignment 2 – Fire Investigation
conditions were similar to those conditions at the time the fire took place. These tests were able to provide
some key information to populate the computer modelling data.
In test fire reconstructions carried out by the BRE and the HFRS, through the opening of the bedroom door
around 22 minutes after the television had caught on fire it was noted that the fire temperature and size
within the bedroom had diminished, producing a rather small fire which needed to be extinguished. However,
3 minutes after the bedroom door was opened a sudden escalation was observed regarding the fire, the
opening of the door was included as this simulated the entry into the room during the rescue operations. In
the test that the BRE conducted, they noted that a dramatic escalation from a small fire to a full room
involvement took place also known as a flashover. At head height temperatures within the bedroom rose from
180◦C to 800◦C, this development took a total of 60 seconds. It’s important to take into consideration the
time-line of fire development in the tests conducted compared with the timings of the actual incident, the
differences are likely to have been from the following factors; wind effect, ambient temperature, ventilation
factors (including both the size and timing of window failure in the bedroom), and stack effect.
A vital question is, what is a flashover which caused this fire to burn so vigorously? Well, a flashover is a term
to describe the sudden involvement of a room in flames from the floor to the ceiling which is caused by
thermal radiation feedback. Thermal radiation feedback is known as the fires energy which is being radiated
back to the contents of the room from the floor, walls, and ceiling. This radiation of energy to the rooms
contents will raise ALL of the contents to their ignition temperature.
Therefore, when the room’s contents ignite simultaneously and suddenly
it’s known as a flashover. A flashover can be described as an event which
is temperature-driven, it needs the energy of the fire to be radiated back
to the contents to produce a rapid rise in relation to temperature and
simultaneous ignition. A flashover indicates that a fire has grown to the
stage where it’s fully developed. Although the opening of the door is
believed to have caused the flashover there are other factors which
could’ve played a role in the flashover and these are; the size of the
room, the combustible contents present, the air supply, and the rooms
insulation – all of these factors can combine and therefore, determine
the flashover potential of flat 85 of Harrow Court.
The bedroom where the fire at Harrow Court originally started wasn’t that large of a room, and was quite
small inside, in relation to a flashover smaller rooms will flash over faster, the reason for this is smaller rooms
tend to enhance thermal radiation feedback faster due to the room’s volume, due to the room being smaller
it’s likely that the contents of the room are in close proximity, thus, increasing the absorption of thermally
radiated energy. The bedroom was also quite full of contents, such as; the bed, the television, the wardrobe,
etc the fact the room was loaded with combustible furnishings will mean that more fire will be produced,
along with more heat and more radiated energy, therefore, more flashover potential. Also, the air supply is
also critical to creating the fire growth to produce flashover, this is because the majority of fires are air
regulated not fuel regulated, the air supply is what’s believed to have been the major cause of this flashover
because this flashover occurred once the firefighters had opened the entrance door and as the bedroom door
wasn’t closed it led to a significant supply of oxygen entering the room and at this time all the contents within
the room were reaching their ignition temperature, causing the flashover to take place. It’s important to note
that the rooms insulation could’ve affected the thermal radiation feedback, due to this the insulation of the
ceilings and walls prevent heat escaping to other areas and increases the flashover potential of the room. At
this fire a ventilation-induced flashover is believed to have taken place, this is where if a compartment
becomes breached through a door or window being opened through a collapse of structure, an oxygen influx
can cause an explosion to occur – in the case of this fire, a door was opened.
Colour/ Temperature of Flame –
During the fire at Harrow Court there was some rather distinct colour flames which were observed rather than
the usual orange/yellow colour from the flames which were produced. A flame gets it shape due to the pull of
gravity drawing colder and denser air down to the base of the flame, through this it displaces the hot air (this
rises.) Fresh oxygen through a process known as convection is fed to the fire, this will burn until the fuel runs
out. Due to the upward air flow it gives the flame its teardrop shape along with causing it to flicker. There are a
variety of colours associated with flames. In reality, there isn’t a single temperature for fire because the
amount of thermal energy that is released is dependent on many factors the reaction products which are being
generated, the chemical composition of the fuel, which is being burnt, and the heat at which its burning. The
colour of the fire is essentially just a rough gauge of how hot it is. For example; a deep red fire is around 600-
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