Fire behaviour & FF safety Flashcards
how does the body lose heat?
convection, radiation, evaporation, conduction
name the types of heat stress
heat exhausation,
heat syncope (fainting),
heat stroke
what are some ways to control heat stress?
info & training
health monitoring
acclimatisation
aerobic fitness
hydration/nutrition
dressing down procedures
achievable briefs
duration of BA work reduced
individual risk assessment
BA welfare log
rehydration (1L inside 60 mins)
accelerated cooling/rehab vehicle
what is the purpose of the BA shuffle?
to provide a safe system of moving through a hazardous environment (obscured visibility/heath) whilst searching for casualties and/or firefighting
what are some hazards you may encounter when working in smoke and darkness?
uneven ground
changes in floor level
holes in floor
furniture
electricity
sharp objects
USE THE BACK OF HAND TO TOUCH OBJECTS
what are the stages of fire development?
initial fire
developing fire
flashover
fully developed fire
decay
extinction
why is oxygen/ventilation important to control?
as oxygen levels drop the flaming combustion eventually stops, but smouldering/incomplete combustion remains, this causes an INCREASE in unburnt products of combustion and fire gases
so visibility is poor, and more unignited flammable gases exist in a compartment
when a door or window breaks or is opened, the fire will increase in intensity and return to flaming combustion
how does the position of fuel in a room affect the fire?
fire in the centre of a compartment or in open air has 100% fresh air available
fire against a wall has 50% of the air available to it
fire in the corner of a room has 25% of fresh air available to it
how does the compartment size affect heat dispersal?
a larger compartment will take longer for it’s average temperature to rise
a compartment with high ceilings may increase the distance from the hot gases at ceiling height and other combustible materials at ground level
wall/ceiling insulation also affects heat disperal
name the phenomena of fire progression
flashover
backdraught
fire gas ignition/explosion
wind driven
what is a flashover?
a sudden and sustained transition of a growing fire to a fully developed fire
plentiful supply of oxygen, heat and fuel
ventilated compartment
tongues of flame visible in smoke layer
high neutral plane moving down
sig. thermal radiation from above
surfaces giving off visible smoke and gases (pyrolysis)
a rapid increase in compartment temperature
name control measures for a flashover
door entry procedures assessment
gas cooling techniques to cool, reduce and dilute
cooling of combustible items showing signs of pyrolysis
what is a backdraught?
a backdraught is a ventilation reduced ignition of fire gases leading to a sudden deflagration*
*rapid burning of fuels
heat, fuel, insufficient oxygen
under ventilated compartment
fire gases pulsing out from gaps
windows blackened with no visible flames
pressure evident when door is opened
whistling noises
low neutral plane
dense smoke with no visible sign of flames
name control measures for a backdraught
tactical ventilation to induce a potential backdraught in a safe way…BUT NOT if a saveable life exists within the structure
> door entry procedures can be used to mitigate the conditions prior to entry
> gas cooling techniques to cool, reduce and dilute
> use of a TIC to identify seat of fire and temps
> consider a safety withdrawal
> consider defensive firefighting tactics
Name the fire classifications
Class a - ordinary combustible fire (water and foam)
Class b - flammable liquids - foam
Class c - flammable gases - isolate at source, extinguish secondary fire
Class d - metal fires - type d powder
Class e - electrical fires - isolate at source, extinguish secondary fire
Class f - cooking oil fires - fire blanket
How does water extinguish a fire?
Water has the greatest latent heat of all liquids
Water has a high specific heat capacity (energy required to raise it by one degree Celsius)
The combined effect of specific heat capacity and latent heat of vaporisation allows water to absorb the energy of the fire
How does water effect the fire gases?
Reduce dilute and cool
Cool = bring gases out of their flammable range
Describe the different ways of gas cooling a fire
GAS COOLING
A water spray/pulse is aimed directly into the hot gases to reduce, dilute and cool them. Helps to reduce heat output and helps maintain bearable conditions for firefighting
INDIRECT METHOD
water spray is applied into the hot gases AND the compartment boundaries to remove heat from boundaries and cool the compartment
DIRECT METHOD
applying water directly at the fuel base of the fire and any combustible items within a compartment which are not yet involved. Control the heat release from the fuel base
What’s the purpose of a door entry assessment?
To assess conditions within the compartment and decide what action to take. To go in and proceed, to not go in and gas cool to make conditions safe to proceed, or to keep door closed and inform OIC of the conditions (red hot) because the risk of firefighting is too high
What are the 3 H’s of a door assessment?
Heat
Hinges
Handles
Heat - any indicators of heat such as blistering paint, noise, TIC
HINGES - hinges visible, open towards or away?
Handles - identify type of handle does the door open towards or away?
How to calculate TAP?
Divide cylinder pressure by 2
Add 30
Round up to nearest ten
When might we send a radio message?
New compartment
Change of levels
Decision needs/has been made
Located a fire
Located a casualty
Located a fatality
When would you check the air gauge?
Upon entry
Before a Change of level
New compartment
Key landmark
At the ECP to calculate individual TAP
What is a fire gas ignition?
The ignition of accumulated fire gases already within their flammable range
Fuel, oxygen, insufficient heat or absence of ignition source
Signs of FGI
accumulation of flammable gases in a location primarily remote from the fire compartment that requires an ignition source e.g. Blaina
Similar signs to backdraft but has ventilation, may not have high pressure levels
CONTROL MEASURES ARE THE SAME AS BACKDRAUGHT
What is a wind driven fire?
A fire which has been impacted directly by the external wind conditions, leading to extremely rapid fire development
More prevalent at high rise fires, can occur at ground level
Control measures are to withdraw BA teams and attempt to isolate the fire compartment
Explain the range of flammability
A flammable gas will only burn if it’s composition lies between certain limits
If too little or too much fuel is present burning will not take place - too lean or too rich
Every fuel/air mixture has an ideal mix at which point combustion will be at its most efficient
Lower explosive limit - lowest concentration of fuel in air that will support a self propagating flame
Upper explosive limit- highest concentration of fuel in air that will support a self propagating flame
Ideal mixture - most efficient mix of fuel and air for combustion
Explain flash point, fire point and auto ignition temperature
Flash point - lowest temperature at which a material has enough flammable vapour that it will give a momentary flash in the air IF AN IGNITION SOURCE IS PRESENT
Fire point - minimum concentration of a flammable material within the air that, once ignited, will be self sustaining
—typically 5-10 degrees celclius above flash point
Auto ignition temperature - lowest temperature at which a solid, liquid or gas will ignite WITHOUT AN IGNITION SOURCE
explain what pyrolysis is
the breakdown of fuel within a fire
when the correct mix of oxygen and heat are applied to a fuel, a chemical reaction results in the molecular breakdown of the fuel.
understanding pyrolysis and the resulting chain reaction and continuation of a fire is vital for firefighters to understand so they can respond to the development of these conditions, react, fight the fire and stay safe.
what does RIDDOR stand for?
Reporting of Injuries, Diseases and Dangerous Occurrences Regulations
what is reportable under RIDDOR? and what is not?
REPORT malfunctions found during checks or whilst using - before, during or after use in a contaminated environment
DO NOT REPORT malfunctions found during checks or whilst using - when used for training and NOT entering a contaminated atmosphere or confined space
