8. Fire, CO and explosions

Question 1

What is The Fire Triangle made of

Answer 1

1. fuel
2. oxygen
3. ignition

Question 2

Give examples of fuel

Answer 2

solid: wood, paper
liquid: petrol
3. gases: methane

Question 3

Give example of ignition:

Answer 3

to start the fire off: flame, spark, hot sruface, radiant heat, chemical

Question 4

How do people die in fire (or are injured in them)? (3)

Answer 4

1. most common: smoke inhalation
2. burn
3. other injuries

Question 5

what toxic gases are found within smoke (3)

Answer 5

a bruning fire produces a great deal of smoke. anyone alive inside will be forced to breathe it in.

the smoke contains various toxic gases:
1. CO (most people die from this)
2. cyanide
3. nitrites

Question 6

Mechanism of action of carbon monoxide

Answer 6

1. produced in all fires and a product of incomplete combustion
2. toxic levels can build up very quickly
3. breathed into the lungs and gets into blood stream where it combines with Hb to form carboxy-haemoglobin
4. haemoglobin has a much greater affinity for CO than O2
5. carboxy-haemoglobin is of no use to the body i.e. the cells cant use it, so decreasing levels of oxygen have serious effect

Question 7

normal level of CO in blood and abnormal

Answer 7

1. normal level is up to 5% particularly in cigarette smokers
2. when levels build up to 50% or above, as in a fire, they are likely to be fatal
3. even lower levels if person has a significant natural disease

Question 8

evidence of smoke inhalation

Answer 8

1.soot in the airway- a lining of black soot all the way down the trachea
2. raised level of CO in the blood (makes the blood and tisses red and makes external lividity pink)

Question 9

people tend to die from burning in one of two circumstances (time)

Answer 9

in the fire: from physiological shock (a car fire or other flashover)

later in the hospital: from fluid loss, biochemical distrubance or infection

Question 10

list factors that determine survival of those reaching hospital (3)

Answer 10

1. severity and extent of burning
2. co-existing illness
3. age

Question 11

how do we classify burns

Answer 11

by depth and extent of burning

Question 12

describe classification of burns by depth:

Answer 12

superficial, part thickness, deep

appereances range from: reddening of the skin -> blistering -> epidermal loss -> subcutaneous tissue loss

Question 13

how do we evaluate extent of burning?

Answer 13

we use the rule of 9s
rough general rule:
if the age of the person + percentage burning is >100, they are less likely to survive

Question 14

what are the possibilities of people not escaping fire?

Answer 14

• overcome by fumes at an early stage e.g. asleep
• intoxicated and unaware of the fire
• physically disabled, bedridden or injured
• did not want to, i.e. suicide

Question 15

What are the reason a person is dead before the fire (2)

Answer 15

1. from natural causes (and their death triggered a fire e.g. cooker or a heater left on)
2. homicide (the person has been murdered and the house set on fire to conceal the crime)

Question 16

List 4 questions the pathologist will consider when dealing with a body or bodies from a fire

Answer 16

1. Who is it
2. did they die as the result of the fire and, if so, in what way
3. was there any reason why they did not manage to get out of the fire?
4. if they did not die from the fire then how did they die and were they dead beforehand?

Question 17

how to check who is the victim in fire?

Answer 17

bodies can suffer severe post mortem damage before being recovered.

identification will clearly be an issue here and will require the usual methods of personal possesions, x-rays, dental and DNA

Question 18

what are we looking for when we suspect the person died as the result of fire

Answer 18

evidence of inhalation of smoke and gases CO, burning and trauma

Question 19

what are we looking for if we think that there must be a reason they did not manage to get out of the fire

Answer 19

intoxication, illness, trauma, suicide

Question 20

in what situations could we suspect carbon monoxide poisoning? (2)

Answer 20

1. accidental (using heater or generators that are faulty or in an enclosed space - shed, tent)
2. suicide - inhaling fumes from a car exhaust , lighting a portable barbecue set in an enclosed room

Question 21

symptoms of carbon monoxide poisoning

Answer 21

nausea, abdominal pain, headache, drowsiness, confusion, unconsciousness

Question 22

what are the most common causes of explosions?

Answer 22

in many countries bombs
in UK gas leak

Question 23

when do explosions occur?

Answer 23

when there is a sudden release of previously confined energy
- energy which has been stored either within a chemical substance or physically compressed within a container
- the release is accompanied by a lot of heat, noise and shock waves

Question 24

describe mechanical explosion

Answer 24

when pressurised material suddenly excapes in an uncontrolled way - > sudden excape of gas or liquid from a steam boiler, LPG container, coprassed air cyllinder

Question 24

List two types of explosions

Answer 24

mechanical and chemical

Question 25

Describe chemical explosions

Answer 25

when a chemical reaction produced heat and gas faster than the surroundings can deal with them

Question 26

two forms of chemical explosions

Answer 26

dispersed (combusting materials are unconfined e.g. gases, fine dust)
condensed (chemical reaction occuring in a solid or liquid)

Question 27

example of dispersed chemical explosion

Answer 27

leakage or dangerous mix of gases in a :
domestic or industrial gas supply
mine shaft or tunnel
petrol bomb

Question 28

what are the characteristics of chemical explosives?

Answer 28

they are directional rather than generalised
they have specific point of origin, meaning that the most of damage is done close to the source, and damage is less further from source

Question 29

what are 2 types of chemical explosives?

Answer 29

1. low explosives (deflagrating) e.g. gunpowder and pyrotechnics

burning of the material in an enclosed space produces an explosion

2. high explosives (detonating) e.g. TNT, RDX, nitroglycerine

• where the explosion is caused by a shock wave passing through the material and disrupting its molecules

Question 30

what are 3 effects of an explosion of any type?

Answer 30

1. physical trauma
2. blast (pressure wave striking the body and passing through it)
3. heat (radiation of heat causing scalding and depper burns)