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50 Cards in this Set
- Front
- Back
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What is the Def'n for Backdraft?
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BACKDRAFT- is the intoduction of O2 to a confined space that is pressurized with heated, flammable gases that are deficient in oxygen, thereby resulting in an explosive force.
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What is the Def'n for Flashover?
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FLASHOVER- is "the simultaneous combustion of the combustible substances in a room heated to their ignition points"
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What is the Def'n for Ventilation?
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VENTILATION- the systematic clearing from a structure, vessel, or other area of objectionable smoke, heat, or noxious gases through controlled channels, followed by the replacement of cooler air, which facilitates other firefighting priorities.
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What are the charcteristics that may indicate a backdraft?
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- smoke under pressure
- black smoke becoming dense gray yellow - confinement and excessive heat - little or no visable flame - smoke leaving the building in puffs - smoke stained windows - muffled sounds - sudden rapid movement of air inward when a opening is made - smoke puffing from cracks and small openings |
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What is the CO explosive range?
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12.5% - 74%
650C |
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Where should the vent opening be to mitigate a backdraft situation?
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As high and as close as possible to the fire.
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Smokes appearance differs greatly depending on what?
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- the materials being burned
- temp. of the fire - the amount of O2 present within the structure |
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What are the 4 visible elements of smoke that help a firefighter assess the fire?
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VVDC
1. Volume- greater the volume, the larger the fire 2. Velocity- greater the velocity the hotter the fire 3. Density- thicker the smoke the more the burning material 4. Colour- may indicate type of material burning but generally the darker the greater the carbon and or toxic material present *Rate of change |
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What are the 2 ventilation strategies and what does each one vent for?
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Offensive - vents for fire, ventilating close to the fire to:
-have a direct effect on the fire itself -limit fire spread -make inside conditions safer for firefighters Defensive - vent for life, ventilating away from the fire or after the fire is out to: -have an effect on hot gases and smoke -improve access and escape routes -control smoke movement away from the areas of the building that are not involved in the fire |
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What are the 4 types of ventilation?
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Vertical
Horizontal Natural Mechanical |
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What are 4 ventilation considerations?
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-the size, extent, and location of the building and fire
- the life hazard - kind of material burning - susceptibility of the material to smoke, heat, and water damage |
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Vertical extension may occur through:
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-stairwells, elevators and shafts by direct flame contact or air convection
- partitions and walls, upward between walls by flame contact or air convection - windows or other outside openings where flame extends - ceilings and floors by direct flame contact -floor and ceiling openings where burning material fall through to lower floors - collapsed floors and roofs |
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Building type and design are 2 major factors to consider in determining when and where to ventilate. Other factors may include:
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-location and size of doors, windows, or other openings in walls
- building size, height, #of stories, staircases, elevators, ducts, and roof openings - use and occupancy of the building - basements and windowless buildings - involvement of exterior fire escapes and other exposures - the presence of HVAC |
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What are the 4 factors to consider when determining the need for ventilation?
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1.Life Hazard
2.Weather Conditions 3.Extent and Location of fire 4.Building Type and Construction |
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Generally it's not necessary to cut a hole in the roof of a private dwelling unless:
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- The fire is in the attic
- a balloon frame - it's extending up the exterior wall |
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When ventilating roofs, where should the ladder be positioned and why? Where should it not be?
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- near the corners of the involved structure because this is one of the strongest parts of the building
- Don't put ladders adjacent to windows/other openings because fire/smoke may hinder descent |
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What is the "Stack Effect"
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- the natural convective movement of heated gases upwards
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When opening a roof what are 7 safety precautions?
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1.Provide a secondary means of escape.
2.Have a charged line in place. 3.Don't walk on a spongy roof. 4. Use caution around elctrical lines 5.Stand on the windward side of the cut. 6.Wear PPE 7.Watch for personnel within the axe swing. |
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Common factors that can destroy the effectiveness of ventilation are:
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-improper use of forced vent
-breaking glass -improperly directed fire streams -breakage of skylights -an explosion -a burn that creates additional openings between the attack team and the upper openings |
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Elevated streams above vent openings should be?
What will this accomplish? |
-projected slightly above the horizontal
-This will help cool the thermal column and extinguish sparks and aid the ventilation process |
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List 2 problems FFface with tile roofs:
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-a lot of damage is caused by walking on it
- broken tiles make a difficult walking surface and create a safety hazard to those below |
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What should be used on a tile roof to give a FF good footing? What is the best tool for tile roof ventilation?
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- roof ladder
- sledge hammer |
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What are 2 indications of a spongy roof?
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1.Sagging when walked on
2.Lack of resistance to an axe |
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Structures which horizontal ventilation is normally applied to?
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-residential buildings in which fire has not involved the attic
-buildings with high windows near the eaves -attics/res. buildings with lowered vents in wall -involved floors of multi-storied structures -buildings where fire is not contained by fire curtains - structures weakened by effects of burning |
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Describe the proper procedure for opening windows for natural ventilation:
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First open top windows on leeward side, after allowing hot gases to escape open the lower windows on the windward side.
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List situations that may require forced ventilation?
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-cond. untenable for FF because of heat, smoke, or toxic atmosphere
-construction unsuitable for Nat. vent. due to lack a vertical shafts or horizontal openings -a fire below ground level or in confined space -a need to remove undesirable atmospheres from areas when there is no fire eg. tunnel, basement, and other enclosures |
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Some disadvantages of forced ventilation are:
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-requires the use of a mechanical device, power source, additional FF
-can increase intensity of fire, and lead to unwanted fire and smoke spread -requires a very large fan for large incidents -provides limited airflow in defensive vent. |
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Before implementing PPV, the following critical requirements must be met:
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-establish a exhaust opening, should be 3/4 to 1 3/4 the size of intake opening
-establish a clear channel from the point of entry to the exhaust opening -determine the location of the fire -position attack lines including exhaust -notify IC and any interior crews |
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2 disadvantages to gas powered fans?
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- noisy
- produce CO |
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What reading of CO must we take immediate action?
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25 PPM or higher.
Hgh Alarm >50 PPM - Source identified, Evacuate and ventilate Source unidentified same but call Haztech as well. Low Alarm 25-50 PPM consider evac. try to identify source and ventilate <25 PPM ventilate and try to identify the source >=12 PPM evacuate small children, pregnant women, seniors, and anyone with respiratory problems, try to identify the source |
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Buildings with multiple stories can be be ventilated by:
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-sequentially ventilating each floor
-start from the lowest contaminated floor and work towards the top |
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What is PPA?
How does it work? |
- Positive Pressure Attack and is used during the initial stages of an incident to make the structure safer for fire attack
-1 or more high output fans directed into the building to increase pressure relative to atmospheric pressure - carries smoke, toxic gases, and heat out an exhaust opening located as close to the fire as possible - controlled and directed through the IC |
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What is PPV?
How does it work? |
- Positive Pressure Ventilation, works similar to PPA however it is used for purposes other than fire attack. eg. overhaul, clear hazardous gases from the structure
-controlled, directed through IC |
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What is PPP?
How does it work? |
-Positive Pressure Pressurization used to over-pressurize and enclosed compartment, thereby preventing additional smoke, toxic gases, and heat from entering the area
- no exhaust opening -controlled, directed through IC |
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What is Natural Ventilation?
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- as the volume of smoke increases it moves through available openings such as doorways and hallways, if a window is vented the smoke and heat begin to spill out that window
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What is Horizontal Ventilation?
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-when crews use doors, windows, and other openings to direct smoke, gases, and heat through the building in a horizontal direction
- horizontal is the most common |
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What is Vertical Ventilation?
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-when crews cut an opening above the fire to direct smoke, gases, and heat upward
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Hows does PPA and PPV render the structure safer for responding crews and victims?
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- it improves visibility, removing toxic gases, and lowering the temp.
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What are the 4 phases of fire?
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1. Ignition
2. Growth 3. Fully Developed 5. Decay |
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What is a Fuel controlled fire?
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- a fire that has excess air for combustion
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What is a Ventilation controlled fire?
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- a fire that produces more vapours that can consumed with the available air
- highly volitile |
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How much % more air does 2 fans placed one behind the other create?
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30%
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What fan configuration creates the highest air volume?
How much % more than in series? |
V-Point
10% more than in series. |
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Does a FF have to stay with the fans while they are in operation>?
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Yes, the whole time. Not to be left unattended.
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What is the Purpose of PPA?
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-to reduce the risk of backdraft or flashover occuring
- to facilitate rescue - to make an area more tenable for victims and firefighting -to remove toxic, explosive, and superheated gases - to confine the fire -to enable crews to advance more rapidly to the seat of the fire -help protect FF's who are extinguishing the fire by removing steam |
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When would PPA be required?
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-conditions are untenable for FF entry due to heat, smoke, and toxic gases
- construction is unsuitable for natural ventilation due to the lack of vertical shafts or horizontal exterior openings - the fie is below ground level, in a confined space, or where difficult to gain entrance - IC deems PPA advantageous |
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PPA may not be appropriate if?
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-signs of impeding backdraft are apparent
- fire location has not been established - windows for venting are inaccessible -wind direction, velocity would make PPA dangerous - victims in exhaust opening, needed for rescue later on - exposure issues that can't be controlled - IC deems PPA disadvantageous |
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What are the steps to setting up PPA?
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1. Locate the fire.
2. Advance a charged line to the entrance. 3. Bring the fan to the entrance. Position sideways and turn on to ensure it's working. 4. Advance a charged line to the planned exhaust opening. 5. Make an exhaust opening as close to the fire as possible, 3/4- 1 3/4 the size of the entrance. 6.Upon direction of the IC turn fans to face the entrance. Check air cone. 7. Obtain a report from exhaust supervisor assessing effectiveness of ventilation. 8. If effective proceed with fire attack. |
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What are some possible problems if during PPA smoke is not flowing toward the exhaust opening?
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- path from entrance to exhaust may not be clear
- wind may be overcoming the fan - may be a closed door |
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What are some potential problems caused by PPA?
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- if the door is not completely sealed or the exhaust opening is inadequate convection may occur leading to more rapid set of flashover
- if a exposure line is directed in the exhaust opening rather than across it may spread the smoke and fire onto interior crews - if the exhaust opening is not monitored nearby exposures and personnel may be put in danger |
