Urban Fire Flashcards
At a factory fire, gas cylinders are being impacted by fire and there is a high risk of a BLEVE occurring. Define the acronym BLEVE and describe how it occurs.
Boiling Liquid Expanding Vapour Explosion.
When a cylinder containing a liquid is impacted by fire the liquid inside heats up and begins to boil and the vapour begins to expand. If the cylinder is not cooled and is unable to vent quickly enough to relieve the pressure build up the cylinder can rupture and the contents explode.
On arrival at an incident involving a backyard bbq cylinder on fire, identify the correct steps you would take to combat the scenario.
Approach from upwind.
Assess condition of the cylinder.
Cool the cylinder (until no streams forms), protect exposures, contain the fire.
Extinguish the fire by shutting off cylinder valve (if possible).
Do not extinguish a flame if leak can not be isolated.
Explain and describe what the ACRONYM AIT stands for? What is the concern for you as a firefighter if you identify objects approaching their AIT?
Auto ignition temperature.
The temp which the air/fuel mix will ignite without the application of a spark or flame. Flashover.
List in order the six stages of branch control
1)turn the branch to full spray to avoid any jet reaction.
2) Rotate branch to full flush
3) turn on branch
4) call and signal for “water on”
5) adjust to required flow rate
6) adjust spray pattern for task
When FF at a bushfire incident in conjunction with fixed-wing or rotary aircraft, what are the precautions you can take to ensure safety of you and your crew?
Maintain correct PPC
Move away from the line of fire when directed by ground controller or sector commander.
Maintain radio vigilance
Only return to fire line when instructed by ground controller or sector commander.
If you are caught in the drop zone;
Watch out for dead branches and hay may fall from overhead.
Place hand tools well clear.
Ensure your helmet is on and secure.
Watch your footing
Wash with cold water if hit by foam.
3 general properties of gas and 4 measures to try and combat gas leak.
General properties:
Gases are compressible
Gases fill any container
Gases expand on heating
Combat:
1)turn off supply if possible
2) eliminate ignition sources
3) dilute- air, water sprays
4) disperse with water sprays
Fire at shopping centre with a installed fire safety system, sprinkler system will:
Detect the presence of fire.
Identify the area involved in fire.
Raise the alarm for both occupants and FB.
Control the fire.
During overhaul at a structure fire, you see vital evidence that has been moved to a safer location. What are the procedures before doing so?
-advise the IC and investigator.
-document the location and configuration of the evidence before moving and photo.
- remove as intact as possible to a secure location.
- avoid contaminating the evidence.
Zone 2 automated response zone, what aerial resources automatically activated.
2 x water bombers
1 x air attack supervisor
Four prerequisite for ground controller.
-a sound knowledge of bushfire fighting strategies and tactics
- ability to read and interpret maps and charts
- ability to quickly assess a bushfire situations and the effectiveness of suppression and make recommendations.
- have clear and concise radio communication skills.
4 stages of combustion
1) incipient stage: decomposition (pyrolysis) is occurring at the surface level due to some form of heat. Products of combustion invisible to the eye.
2) Smouldering: heat increases, more fuel matter decomposes giving off more smoke but still no flames, products released at the surface become visible as smoke.
3) Flaming: Vapours from the decomposing fuel have ignited and flame continues to burn giving off heat and light. Fire is now self sustaining, heat produce is sufficient to release more vapours to feed the flames.
4) Heat: combustion has reached the point where the fire is much more rapid and creating considerable heat. Heat is then transferred to the atmosphere and nearby matter which can cause vapours to be given off other combustibles causing fire to grow.
As fire gases reach their LEL, what are the types of ignition sources that may cause explosion.
-open
-intermittent
-concealed
-auto ignition temp (AIT)
Door entry procedure
-covering stream, always have extinguishing equipment tested and ready before attempt
-Direction of opening, check hinges.
- Scan door, with TIC to give indication of heat within compartment and neutral plane, make a risk assessment.
-paint door, apply water to door to give an indication of heat/neutral plane, risk assessment.
-safe position, adopt a safe position using door or wall as protection.
-back of hand, test door handle with gloves hand.
-pulse spray above hinge side and opening side, immediately before opening to cool gases.
-open door, keep opening as small as possible, observe inside conditions and risk assess.
-cool gases, immediately on opening door.
-Close door, reassess and repeat sprays if cooling still req.
-when assessment is good, plan entry.
Drop in pressure on compound gauge, from reticulated supply
1) burst collector
2) hydrants being turned off
3) blocked collector
Light tanker, bushfire, loss of comms, how to re establish comms?
-Check radio turned on/up and on correct channel
- move to another location, higher ground
- try to use another crews radio
- try to contact another crew to relay message.
3 priorities at a bush fire
1)Preservation of life, will influence what suppression strategy to use.
2)protection of property, houses, infrastructure (electrical/telephone lines) bridges, livestock
3) protection of environment, reserves, forests, undeveloped land.
3 disadvantages of foam
-Requires total flushing of all equipment used in the production of foam.
-can be expensive
-application can be affected by strong winds
-may be harmful to environment.
Class C fire
Compressed gas fire:
- do not extinguish flame
- cool cylinders from a distance using sprays and protecting exposures.
- take cover if possible and approach from sides
- isolate supply to extinguish fire.
Heat build up should not be used as a warning for flash over, what are other early signs?
Downward movement of the neutral plane
- darkening if the smoke colour
- increase in the air track ‘roaring noise
- lengthening/pockets of flame colour.
Effects of increase temp on water
Water turns into steam and expands, expansion rates are:
100 degrees: 1:1700
600 degrees: 1:3400
Too much water application = too much steam and be detrimental to compartment occupants. Destroys thermal balance and visibility.
6 causes of not achieving max theoretical suction.
1)friction loss: from hose and strainer.
2) Entry loss: due to turbulence as water enters impeller.
3) pump efficiency: centrifugal pumps are not 100% efficient.
4) density of water: salt water denser.
5) temp of water: hot water tends to vaporise in the suction and effect pump.
6) Altitude: altitude increases, air is “thinner” and pressure becomes lower.
Signs of backdraught
-blackening of the windows
-whistling noises
-very low neutral plane
-flames in smoke outside the room
-changes in the air track.
To avoid backdraught gas cool and do not ventilate until safe to do so or directed by OIC
3 types of fire streams and pros and cons
Jet:
Pros: Longer reach, greater penetration, least affected by wind/radiant heat
Cons: jet reaction, can cause damage, may conduct electricity, may spread the fire, uses lots of water.
Spray:
Pros: water curtain for protection, accelerates water converted to steam = removing heat from surrounding fire, covers larger area = more economical, less tiring to hold
Cons: shorter reach, less penetration.
Fog:
Pros:covers larger surface area, absorbs heat rapidly, minimises damage to property, maximises effectiveness of water, protection to FF from radiant heat, less tiring to hold.
Cons: shorter reach, affected by wind, impede visibility, fog to steam = increase heat
Whistling noise from inside a compartment inside a structure fire?
Air is being drawn into the compartment, may be a sign if backdraught.
