Fire ventilation

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would be the case, for example, in apartment fires or in certaintypes of industrial buildings where it is difficult, or infact impossible, to create openings in the roof and wherethere are no skylights or vents.Vertical fire ventilationThis is where the outlets are above the fire, often as high aspossible in the building so that the flow of fire gases takesplace vertically. The outlet is normally implemented bymaking an opening in the roof structure, or by using existingvents (windows/apertures or vents/shutters).Top left: a window inthe fire room can beused for horizontal fireventilation.Top right: fans can beused to achieve mechanicalfire ventilation.Mechanical fire ventilationThis can mainly be implemented as positive pressure ventilationor negative pressure ventilation. The mechanicalventilation must be combined with creating openings, so asto achieve horizontal or vertical ventilation.13
Fundamental principlesFire ventilation influences a fire by supplying more air,whereby the intensity of the fire increases. Conversely thisof course means that a fire can in certain cases be containedif there is no fire ventilation. Nevertheless fire ventilationseldom has a negative effect on the results of a fire andrescue operation seen as a whole, on the assumption thatthe ventilation measures are coordinated with other measures,such as for example suppression. Fire ventilation mayaggravate the situation for a time, but also makes it possibleto influence the fire in such a way that any problems can bebrought under control. In all likelihood other and moresevere problems would occur if fire ventilation had notbeen implemented at all. Fire ventilation should, however,be implemented in the right way, at the right place, and atthe right time, and be coordinated with other measures,above all extinguishing.It is often of critical importance for the results of fireventilation whether the fire is fuel controlled or ventilationcontrolled when the measure is implemented. A fuel-controlledfire is essentially controlled by the amount of fueland how the fuel is positioned, while a ventilation-controlledfire is essentially controlled by how much air the fire hasaccess to. If fire ventilation can be implemented at an earlystage of the fire scenario, i.e. when the fire is still fuel controlled,this can prevent or at least delay ventilation control.It would be the same thing to say that very often a fullydeveloped fire can be avoided, or at least delayed. Combinedwith powerful and rapid suppression measures, thisFire ventilation should be implemented as soon aspossible during the fire and rescue operation.It is often of critical importance for the outcomewhether the fire is fuel controlled or ventilationcontrolled, along with the coordination of othermeasures.14
Page 1 and 2: To carry out fire and rescue operat
Page 3 and 4: The content of this book may not be
Page 5 and 6: Inlets 51Horizontal fire ventilatio
Page 7 and 8: ForewordIn this book fire ventilati
Page 10 and 11: chapter 1Fire ventilationThe fundam
Page 12 and 13: Openings to gain access to a fire t
Page 16: esults in quicker and more simple e
Page 19 and 20: PyrolysisIrreversible chemicaldecom
Page 21 and 22: Flashover results in afully develop
Page 24 and 25: chapter 3Fire gasesFire gases is a
Page 26: Fire gases containsproducts such as
Page 29 and 30: The dynamic pressure differences ca
Page 31 and 32: Pressure differencesproducedby diff
Page 33 and 34: The hydrodynamic pressure differenc
Page 35 and 36: Direction of windnegative pressurep
Page 37 and 38: There can be verycomplex windcondit
Page 39 and 40: In buildings erectedduring the 1960
Page 41 and 42: Calculation of thermal expansionSta
Page 43 and 44: Calculation of thermal buoyancy for
Page 45: The different pressure differences
Page 49 and 50: For practical reasons it can someti
Page 51 and 52: Calculation of the size of outletsT
Page 53 and 54: almost always preferable to strive
Page 55 and 56: The mass flow through the inlet can
Page 57 and 58: Openings andventilation can beimple
Page 59 and 60: When a room or a firecell is consid
Page 61 and 62: 60sure ventilation can also be appl
Page 63 and 64: Negative pressure ventilation is no
Page 65 and 66:
The pressurising of adjacent rooms
Page 67 and 68:
Fans can during positivepressure ve
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A large outlet produces a larger vo
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The volume flow in the outlet is gi
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a hall and no other internal connec
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chapter 6Creating openingsOpenings
Page 78 and 79:
Electric motor powered toolsThe ele
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12 3The circular saw is used to saw
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Water cutting.plastic explosive is
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Lowering deviceFall damperConnectin
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chapter 8Openings in differentroof
Page 90 and 91:
its way through on its own, without
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drop down on personnel standing on
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It is a good idea if the outer open
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A completely manual shutter, often
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In buildings that have systems for
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The measures that areinitiated, coo
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It is only through control that a s
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104
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elatively cold and diluted. Because
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Flashover has still nottaken place
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Flashover has takenplace and the fi
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Piercing nozzle(fog nail).Alternati
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To take into consideration at stair
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Further readingBengtsson, L. (1999)
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Särdqvist, S. (1994). Övertrycksv
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Fire ventilation

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