Lecture 2 Flashcards
Reasons for arson:
- Malicious destruction of property
- Insurance fraud
- Juvenile disorder
- Attempt to harm a person
- Mental health and psychological problems.
- Financial downtick within the economy can cause an increase in arson.
Why are many arson fires started?
As an attempt to destroy evidence including:
- Fingerprints
- FIbres
- DNA evidence
- To mask a murder but usually they can tell if someone had died before or during a fire from CO2 in their lungs.
- Mitochondrial DNA can withstand very high temperature but is more difficult to use for DNA profiling.
Common settings and profiling for arsonists.
- Vehicle fires
- Theft locations
- dwellings to obscure a victims death or destroy physical evidence.
What is the largest cause of major fires in UK and what are the consequences?
- Arson
- Costs £2.8 billion yearly
- Holds a maximum life sentence judicially
- Leads to deaths, injuries and damage
Arson statistics
- There is a 92% chance arsonists will get away with it.
- There is low deterence to stop them
- Detection and conviction rates are low
Arson control forum
- Set up in 2001 by UK government.
- Set up to reduce arson related deaths, injuries and damage.
- Their outlined target was to reduce delibrate fires by 10% before 2010.
- They achieved their target.
- ## They promited and provided education on how to set fires safely.
How did the arson control forum achieve their goal?
- Issued improved interim guidance on fire investigation.
- Published guidance on juvenile fire setter intervention schemes, derelict cars/buildings, refuse and fly-tipped rubbish.
- Helped produce an “Arson toolkit” as part of the home office crime reduction programme.
- They were provided with resources and spent them in a very targeted effient manner.
- Dedicated lots of money to car clearance schemes.
Why did car clearance schemes help reduce arson?
- Derelict cars and buildings are primary things arsonists would set fire to.
- Reduced the number of derelict cars available which reduced the number of fires
- The reduction of fires related to derelict cars can’t be completely down to car clearance schemes as there was also a massive increase in car scrapping values
What did the arson control forum comission research into?
- The motivation of arsonists (which has been published)
- Links between vehicular arson, abandoned vehicles and other vehicle crime.
- Social exclusion and risk of fire.
- Why arson prosecutions “fail”.
What is a key factor in a person likely to become an arsonist?
Social exclusion
How is the arson control forum doing now?
- The Arson Control Forum has now been scaled down, with reduced government funding.
- They aim to achieve a sustained reduction in the number of deliberate fires and related deaths, injuries and property damage.
- A lot of work was done into setting up new innovations so they felt new objectives were needed.
- They shifted their focus to the continued effort to identify and share good practice with a view to improving further efforts across the country.
- Since 2013, rebranded as the Arson Prevention Forum.
What cause of fire would be caused from playing with fireworks?
Accidental
Legal liability
- Fires that can be considered accidental in nature (i.e there is no malicious intent aforethought) can still carry a legal liability (and criminal proceedings).
- This applies to the original cause of the fire, and any factors that assist to its spread.
Legal liability
Infringement of safety legislation and regulations [COSHH]
- Unlicensed storage of fuel or other flammable substances; or storage in unsuitable containers. Or excessive quantities.
Legal liability
Neglect; failure to exercise an employers “duty of care”
Failure to undertake safety to undertake safety inspections
Legal liability
Fire caused as a consequence of committing another crime.
- Illegal bypassing of gas meters
- Use of unqualified gas fitters (corruptly awarded by local council)
Events
Legal liability example
- An explosion at the Stockline plastics factory in Glasgow in may 2004 killed nine people and injured a further 40.
- Propane gas leak from a corroded pipe in the factory basement ignited.
The blast caused the 4 story building to collapse.
Liability
Legal liability example
- Factory operators were fined £400,000 in August 2007 for health and safety breaches.
Causes
Legal liability example
- The responsible pipe was installed in 1969, sealed beneath the cellar floor and installed without corrosion protection.
- The company was additionally neglectful in safety inspections. Instead of hiring a professional consultant for safety inspections, the most up-to-date risk assessment on the gas pipes was performed by a student on a holiday job.
Combustion
- Process of burning
- A chemical change, especially oxidation, accompanied by the production of heat and light.
- Any chemical reaction with the component of heat and light can be classed as combustion
Fire
- Flaming combustion
- A rapid, persistent chemical change that releases heat and light and is accompanied by flame, especially the exothermic oxidation of a combustible substance.
Flame
- The zone of burning gases and fine suspended matter associated with rapid combustion; a hot glowing mass of burning gas or vapour. The condition of active, blazing combustion.
- a region in which chemical interaction between gases occurs, accompanied by the evolution of heat and light.
What conditions have to be met in order for combustion to occur?
- Fuel
- Oxygen
- Heat (specifically enough heat to initiate combustion, i.e ignition source. This is a momentary input of heat energy, not sustained)
- Need enough amount of heat to overcome the activation energy of that process in a small incidental moment
- You need a spark or ignition energy to start the reaction and then you needed the chain reaction to keep occurring for the fire to persist.
Using the heat triangle, how can a fire be extinguished or prevented?
A fire can be prevented or extinguished
by removing one (or more) of the three
components of the fire triangle.
Combustion of methane
Combustion is an oxidation process
CH4(g) + 2O2(g) –> CO2(g) + 2H2O(g or l)
Combustion of aluminium
2Al(s) + 3/1O2(g) –>Al2O3(s)
Oxidation
- Oxidation is an exothermic process i.e one in which heat is liberated.
- The heat that is liberated is called the heat of combustion.
- Enthalpy is the correct energy term at constant pressure
Standard enthalpy of combustion
- Refers to standard conditions (298 K and pressure at 1 atomosphere)
- Denoted as delta Hc0
Oxidation number of pure elements in standard state
- Zero
- H2 = 0
- Cl2 = 0
Oxidation number of monatomic ions
Ionic charge
Oxidation number of halogens
They are very electronegative so they are typically assigned a value of -1.
Oxidation number of hydrogen
Hydrogen is almost always +1. the exception is metal hydrides (MHx) (-1) (eg in sodium or lithium hydride)
Oxidation group of alkali metals (groip 1)
Typically +1
Oxidation number of alkaline earth metals (group 2)
+2
Steps for redox equations
- Determine the oxidation states of each species
- Balance atoms that change oxidation state.
- Determine number of electrons gained or lost
- Balance charges by using H+ (in acidic solution) or OH- (in basic solution).
- Balance the remainder of the atoms (H’s and O’s) using H2O
- Balance the number of electrons transferred for each half reaction using the appropriate factor so that the electrons cancel.
- Add the two half reactions together and simplify where appropriate.
OILRIG
Oxidation is loss of electrions, reduction is gain of electrons
What indicates incomplete combustion
- The prescence of CO instead of CO2
- CO is poisonous and can further combust
Sulfur is an impurity in many fuels. Its complete combustion is very slow, so is rare, but what would that product of complete combustion be?
SO3
