Fire ventilation Not any panacea

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Gilbert Burns
5 years ago
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1 /4/7 ire entilation Not any panacea Stefan Sensson

2 /4/7 nd best moie eer? But, which is the best moie?

3 /4/7 What is a fire and rescue operation? phenomenon in which one or more actions are initiated, coordinated and implemented under the influence of one or seeral commanding officers, often carried out in dynamic enironments. systems perspectie set of interacting components forming an integrated whole he characteristics of a system is different from the characteristics of its components system is more than just the sum of its components n example: the human body he lier is a ital organ We can discuss and look at the lier itself, without looking at the rest But if you take out the lier from the body, it becomes pretty useless 3

4 /4/7 How does this apply to fire entilation? ire entilation is a ital part of a fire fighting operation We can discuss and look at fire entilation itself, without looking at the rest But if we take out fire entilation from the operation, it becomes pretty useless Using fans for putting out fires? 4

buildings o facilitate the operation o stop or to limit the

5 /4/7 What is fire entilation? o ent smoke or hot gases from a space exposed to fire or hot gases, in a controlled fashion! o reduce the impact of heat and smoke to people and to buildings o facilitate the operation o stop or to limit the spread of fire and hot gases o facilitate mop-up and salage How do we do fire entilation? We create openings Existing or new Outlets Inlets 5

6 /4/7 ressure? he flow of fire gases is generated due to differences in pressure rom high pressure to low pressure H L ressures in buildings due to fire hermal expansion hermal buoyancy 6

7 /4/7 low in a room with a small opening low in a room with a large opening 7

8 /4/7 ressure differences creates flow assuming there s an opening here will be a flow of gases between rooms with different pressures here will be a flow within a single room if there are differences in pressure within the room he flow will be from higher pressure to lower pressure dding a fan doesn t change this! So, what happens when we ent? Openings Smoke and hot gases flows out resh air flows in ressure differentials in the building is changed uel control No immediate/obious/distinct influence on the fire Ventilation control Immediate/obious/distinct influence on the fire ire will increase its intensity Increased rate of heat release Rapid flame spread dding a fan doesn t change this! 8

/4/7 9 he Bernoulli equation Describes the relation between pressure and elocity irst law of thermodynamics, conseration of energy, tells us that gh

9 /4/7 9 he Bernoulli equation Describes the relation between pressure and elocity irst law of thermodynamics, conseration of energy, tells us that gh gh tmospheric pressure Hydrostatic pressure Dynamic pressure D D e i D D.. dyn 4 D V π & d C V & dyn ξ h g ξ h g dyn ξ 8 H D V dyn π &.44 D V H V & & ξ π

10 /4/7 >> small large X-axis Y-axis Ventilation factor efficiency Venting, using V % 9% ~9% Ventilation efficiency 8% 7% 6% 5% 4% 3% % ~45% ~7% : : : % %,5,5,5 3 3,5 4 rea of outlet / rea of inlet

/4/7 Venting, without V (thermal entilation) % 9% 8% 7% Ventilation efficiency 6% 5% 4% 3% % % %,5,5,5 3 3,5 4 rea of inlet/rea of outlet large outlet no backflow due to pressure differential in the

11 /4/7 Venting, without V (thermal entilation) % 9% 8% 7% Ventilation efficiency 6% 5% 4% 3% % % %,5,5,5 3 3,5 4 rea of inlet/rea of outlet large outlet no backflow due to pressure differential in the interior opening small outlet backflow due to pressure differential in outlet outlet inlet pressure in the left room larger than pressure in the right room pressure in the right room larger than pressure in the left room

12 /4/7??????? Distance between inlet and fan? here s not really any answer It depends on an size (diameter power ) ype of fan Construction of fan Size of inlet Lay-out of building (!) Consequently: you hae to test eery fan that you buy and learn how it works!

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15 /4/7 Summarizing ositie ressure Ventilation ressure differentials creates flow Outlets should be at least as large as inlets, preferably twice as large No outlet no V! No V no good! 5

16 /4/7 ire entilation is not any panacea! Consider the options, all of the options! Coordination is the key! n integrated approach to fire fighting operations ire suppression ire entilation 6

17 /4/7 hank you! 7

TACTICAL VENTILATION Graeme Bowser, Tyne & Wear Fire Brigade, U.K.

TACTICAL VENTILATION Graeme Bowser, Tyne & Wear Fire Brigade, U.K. Graeme@UKfirefighter.org.uk Ventilation when performed correctly saves lives, eases firefighting conditions and reduces damage. 1. Introduction