Stack effect - Revision history

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	The '''stack effect''' is the movement of air or smoke through a tall building caused by pressure differences that arise from temperature differences.<ref name="IS-F61">Iqbal and Salley (2004), p. F-61.</ref> When the air inside a building is warmer than the air outside, it is lighter, rises through vertical shafts such as stairs and lift shafts, and leaves through openings high in the building. Cold outside air is drawn in low down. This is called the normal stack effect. When the outside air is warmer, the flow reverses and runs downwards, which is called the reverse stack effect.<ref name="KL-274">Klote (2002), p. 4-274.</ref> It is also called draught or chimney effect and is best known from chimneys.<ref name="VR-6.6">Van Rossum (2027), §6.6.</ref><ref name="EV-70">Evans et al. (2005), p. 70.</ref>		The '''stack effect''' is the movement of air or smoke through a tall building caused by pressure differences that arise from temperature differences.<ref name="IS-F61">Iqbal and Salley (2004), p. F-61.</ref> When the air inside a building is warmer than the air outside, it is lighter, rises through vertical shafts such as stairs and lift shafts, and leaves through openings high in the building. Cold outside air is drawn in low down. This is called the normal stack effect. When the outside air is warmer, the flow reverses and runs downwards, which is called the reverse stack effect.<ref name="KL-274">Klote (2002), p. 4-274.</ref> It is also called draught or chimney effect and is best known from chimneys.<ref name="VR-6.6">Van Rossum (2027), §6.6.</ref><ref name="EV-70">Evans et al. (2005), p. 70.</ref>

			[[File:fse-stack-effect-v1.svg\|thumb\|upright=1.5\|alt=Two building sections with a central shaft: left, air enters low, rises in the shaft and leaves high; right, air enters high, falls in the shaft and leaves low.\|Normal stack effect in cold weather (left) and reverse stack effect in warm weather (right). The neutral plane is where the inside and outside pressures are equal. Based on Klote (2002), pp. 4-274 to 4-275.]]

	The stack effect is one of the main driving forces of [[smoke movement]] in buildings, together with the buoyancy of hot smoke, expansion, wind and the ventilation system.<ref name="KL-274" /> It operates even without a fire and acts on the whole height of a building. Its strength grows with the height of the building and with the difference between inside and outside temperature.<ref name="KL-274" /> In a [[high-rise building]] in cold weather, it can carry smoke from a fire on a low floor to floors far above. During the 1993 bombing of the World Trade Center, it was a primary driver of rapid smoke spread.<ref name="KL-276">Klote (2002), p. 4-276.</ref><ref name="FS-xxxiv">Ferreira and Strege (2005), p. xxxiv.</ref> Engineers therefore account for the stack effect when they design smoke control systems, which must keep working whatever the weather.<ref name="KL-285">Klote (2002), p. 4-285.</ref>		The stack effect is one of the main driving forces of [[smoke movement]] in buildings, together with the buoyancy of hot smoke, expansion, wind and the ventilation system.<ref name="KL-274" /> It operates even without a fire and acts on the whole height of a building. Its strength grows with the height of the building and with the difference between inside and outside temperature.<ref name="KL-274" /> In a [[high-rise building]] in cold weather, it can carry smoke from a fire on a low floor to floors far above. During the 1993 bombing of the World Trade Center, it was a primary driver of rapid smoke spread.<ref name="KL-276">Klote (2002), p. 4-276.</ref><ref name="FS-xxxiv">Ferreira and Strege (2005), p. xxxiv.</ref> Engineers therefore account for the stack effect when they design smoke control systems, which must keep working whatever the weather.<ref name="KL-285">Klote (2002), p. 4-285.</ref>
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	The position of the neutral plane depends on where the building leaks. If the leakage paths are spread evenly over the height, the neutral plane lies near mid-height. Where leakage is uneven, for example in shafts vented at the top, it can lie much higher or lower.<ref name="KL-275" /><ref name="KL-276" /> The pressure difference therefore grows towards the top and the bottom of the building and is largest at the ends of the shafts.<ref name="KL-275" />		The position of the neutral plane depends on where the building leaks. If the leakage paths are spread evenly over the height, the neutral plane lies near mid-height. Where leakage is uneven, for example in shafts vented at the top, it can lie much higher or lower.<ref name="KL-275" /><ref name="KL-276" /> The pressure difference therefore grows towards the top and the bottom of the building and is largest at the ends of the shafts.<ref name="KL-275" />

			[[File:fse-stack-effect-v2.svg\|thumb\|upright=1.5\|alt=Straight line of shaft-to-outside pressure difference against height in a 60 m building, from minus 54 Pa at the bottom to plus 54 Pa at the top, zero at 30 m.\|Pressure difference between a shaft and the outside over the height of a 60 m building with the neutral plane at mid-height, at −18 °C outside and 21 °C inside. Based on Klote (2002), p. 4-275.]]

	=== Worked example ===		=== Worked example ===
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	For the same temperatures, the pressure difference increases by about 1.8 Pa for every metre of height from the neutral plane. A 120 m building with its neutral plane at mid-height would therefore see about 108 Pa at its top and bottom. These values are large compared with the pressures used in smoke control. Klote suggests a minimum design pressure difference of 20 to 25 Pa across a barrier next to an intense fire.<ref name="KL-285" /> Codes for pressurisation in the United States require 12.5 Pa in sprinklered and 25 Pa in unsprinklered buildings.<ref name="EV-87">Evans et al. (2005), p. 87.</ref> The buoyancy of the fire gases themselves gives about 13 Pa at 1.52 m above the neutral plane of a fire room at 800 °C.<ref name="KL-276" />		For the same temperatures, the pressure difference increases by about 1.8 Pa for every metre of height from the neutral plane. A 120 m building with its neutral plane at mid-height would therefore see about 108 Pa at its top and bottom. These values are large compared with the pressures used in smoke control. Klote suggests a minimum design pressure difference of 20 to 25 Pa across a barrier next to an intense fire.<ref name="KL-285" /> Codes for pressurisation in the United States require 12.5 Pa in sprinklered and 25 Pa in unsprinklered buildings.<ref name="EV-87">Evans et al. (2005), p. 87.</ref> The buoyancy of the fire gases themselves gives about 13 Pa at 1.52 m above the neutral plane of a fire room at 800 °C.<ref name="KL-276" />

			[[File:fse-stack-effect-v3.svg\|thumb\|upright=1.5\|alt=Falling line of pressure difference per metre against outside temperature from minus 40 to plus 40 °C, crossing zero at 21 °C.\|Stack effect pressure difference per metre of height from the neutral plane as a function of outside temperature, for an inside temperature of 21 °C. Positive values mean normal, negative values reverse stack effect. Based on Klote (2002), pp. 4-274 to 4-275.]]

	Very tall buildings reach much higher values. For the World Trade Center towers, NIST used the New York winter design temperature of −9.4 °C (15 °F). At that temperature, the stack effect pressures were of the order of 280 Pa at the bottom and top of the towers.<ref name="FS-14">Ferreira and Strege (2005), p. 14.</ref> NIST noted that this is an order of magnitude higher than the design pressure for unsprinklered buildings, so the stack effect can contribute significantly to smoke spread in tall buildings.<ref name="FS-14" /> The towers also influenced their surroundings. Under extreme weather conditions, air that entered the PATH railway tunnel in New Jersey left through the top of the towers.<ref name="FS-61">Ferreira and Strege (2005), p. 61.</ref>		Very tall buildings reach much higher values. For the World Trade Center towers, NIST used the New York winter design temperature of −9.4 °C (15 °F). At that temperature, the stack effect pressures were of the order of 280 Pa at the bottom and top of the towers.<ref name="FS-14">Ferreira and Strege (2005), p. 14.</ref> NIST noted that this is an order of magnitude higher than the design pressure for unsprinklered buildings, so the stack effect can contribute significantly to smoke spread in tall buildings.<ref name="FS-14" /> The towers also influenced their surroundings. Under extreme weather conditions, air that entered the PATH railway tunnel in New Jersey left through the top of the towers.<ref name="FS-61">Ferreira and Strege (2005), p. 61.</ref>
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	== Effect on smoke movement ==		== Effect on smoke movement ==
	In a building with the normal stack effect, the existing air currents can move smoke far from the fire.<ref name="KL-276" /> If the fire is below the neutral plane, smoke enters the shafts with the building air and rises, helped by its own buoyancy. Above the neutral plane it flows out of the shafts into the upper floors. If there is little leakage between floors, the floors below the neutral plane, apart from the fire floor, stay relatively free of smoke for a time.<ref name="KL-276" /> If the fire is above the neutral plane, smoke is carried to the outside through openings in the facade. Where floors leak considerably, smoke also moves up to the floor above the fire.<ref name="KL-276" />		In a building with the normal stack effect, the existing air currents can move smoke far from the fire.<ref name="KL-276" /> If the fire is below the neutral plane, smoke enters the shafts with the building air and rises, helped by its own buoyancy. Above the neutral plane it flows out of the shafts into the upper floors. If there is little leakage between floors, the floors below the neutral plane, apart from the fire floor, stay relatively free of smoke for a time.<ref name="KL-276" /> If the fire is above the neutral plane, smoke is carried to the outside through openings in the facade. Where floors leak considerably, smoke also moves up to the floor above the fire.<ref name="KL-276" />

			[[File:fse-stack-effect-v4.svg\|thumb\|upright=1.5\|alt=Section of a tall building: fire on a low floor, smoke entering a shaft, rising and spreading onto the upper floors above the neutral plane.\|Smoke from a fire below the neutral plane is drawn into the shafts by the normal stack effect and spreads onto floors above the neutral plane. Based on Klote (2002), p. 4-276.]]

	The 1993 bombing of the World Trade Center shows how strong the effect can be. The explosion cut electrical power, the ventilation systems stopped, and the outside temperature was in the twenties degrees Fahrenheit, below freezing.<ref name="FS-xxxiv" /> Openings created in lift shafts on the lower levels let smoke rise rapidly to the upper parts of the tower. NIST concluded that the stack effect could be a primary driver of rapid smoke spread in high-rise buildings, and that openings in vertical shafts strengthen it.<ref name="FS-xxxiv" /><ref name="FS-xxxv">Ferreira and Strege (2005), p. xxxv.</ref> Stair doors held open by evacuating occupants increased the airflow up the stairs.<ref name="FS-xxxv" /> On 11 September 2001, fresh air drawn up from lower floors by the chimney effect also supplied oxygen to fires deep inside the towers.<ref name="MG-52">McGrattan et al. (2005), p. 52.</ref>		The 1993 bombing of the World Trade Center shows how strong the effect can be. The explosion cut electrical power, the ventilation systems stopped, and the outside temperature was in the twenties degrees Fahrenheit, below freezing.<ref name="FS-xxxiv" /> Openings created in lift shafts on the lower levels let smoke rise rapidly to the upper parts of the tower. NIST concluded that the stack effect could be a primary driver of rapid smoke spread in high-rise buildings, and that openings in vertical shafts strengthen it.<ref name="FS-xxxiv" /><ref name="FS-xxxv">Ferreira and Strege (2005), p. xxxv.</ref> Stair doors held open by evacuating occupants increased the airflow up the stairs.<ref name="FS-xxxv" /> On 11 September 2001, fresh air drawn up from lower floors by the chimney effect also supplied oxygen to fires deep inside the towers.<ref name="MG-52">McGrattan et al. (2005), p. 52.</ref>

Daan: New FSE wiki article: Stack effect (written by Claude Opus 5.5)

2026-11-01T22:53:07Z

New FSE wiki article: Stack effect (written by Claude Opus 5.5)

New page

The '''stack effect''' is the movement of air or smoke through a tall building caused by pressure differences that arise from temperature differences.<ref name="IS-F61">Iqbal and Salley (2004), p. F-61.</ref> When the air inside a building is warmer than the air outside, it is lighter, rises through vertical shafts such as stairs and lift shafts, and leaves through openings high in the building. Cold outside air is drawn in low down. This is called the normal stack effect. When the outside air is warmer, the flow reverses and runs downwards, which is called the reverse stack effect.<ref name="KL-274">Klote (2002), p. 4-274.</ref> It is also called draught or chimney effect and is best known from chimneys.<ref name="VR-6.6">Van Rossum (2027), §6.6.</ref><ref name="EV-70">Evans et al. (2005), p. 70.</ref>

The stack effect is one of the main driving forces of [[smoke movement]] in buildings, together with the buoyancy of hot smoke, expansion, wind and the ventilation system.<ref name="KL-274" /> It operates even without a fire and acts on the whole height of a building. Its strength grows with the height of the building and with the difference between inside and outside temperature.<ref name="KL-274" /> In a [[high-rise building]] in cold weather, it can carry smoke from a fire on a low floor to floors far above. During the 1993 bombing of the World Trade Center, it was a primary driver of rapid smoke spread.<ref name="KL-276">Klote (2002), p. 4-276.</ref><ref name="FS-xxxiv">Ferreira and Strege (2005), p. xxxiv.</ref> Engineers therefore account for the stack effect when they design smoke control systems, which must keep working whatever the weather.<ref name="KL-285">Klote (2002), p. 4-285.</ref>

== Physical principle ==
The stack effect is a form of [[buoyancy]]. When air is heated, its density falls, so a column of warm air weighs less than a column of cold air of the same height. The heavier cold air pushes the lighter warm air upwards.<ref name="VR-3.2">Van Rossum (2027), §3.2.</ref> The book names buoyancy as the driving force behind smoke plumes, the stack effect and natural smoke exhaust. The larger the difference in density and the greater the height, the larger the pressure difference in general.<ref name="VR-3.2" />

The density of air follows from the [[ideal gas law]]. At atmospheric pressure it is approximately 353 divided by the absolute temperature in kelvin, which gives about 1.2 kg/m³ at 20 °C.<ref name="VR-3.2" /> The pressure in still air increases with depth, by the weight of the air above. Inside and outside a building, the pressure therefore changes with height at slightly different rates, because the two air columns have different densities.<ref name="VR-3.2" />

At one height, the pressure inside equals the pressure outside. This level is called the [[neutral plane]].<ref name="KL-275">Klote (2002), p. 4-275.</ref> In the normal stack effect, the inside pressure is higher than outside above the neutral plane, so air flows out there. Below the neutral plane, the inside pressure is lower, so outside air flows in.<ref name="KL-275" /> The book describes the same pattern for a room with openings: air flows in below the neutral plane and smoke flows out above it.<ref name="VR-3.2" />

A chimney strengthens the effect because no horizontal mixing can take place inside it.<ref name="VR-6.6" /> In buildings, the stairs, lift shafts, service shafts and mail chutes act as chimneys. Klote notes that the normal stack effect matters most at low outside temperatures and in tall shafts, but it can even exist in a one-storey building.<ref name="KL-274" />

== Pressure difference ==
The pressure difference grows linearly with the distance from the neutral plane and with the difference between the reciprocals of the two absolute temperatures. Klote gives it for a shaft and the outside air as follows:<ref name="KL-274" /><ref name="KL-275" />

<math display="block">\Delta p = K_\mathrm{s} \left( \frac{1}{T_\mathrm{o}} - \frac{1}{T_\mathrm{i}} \right) h</math>

{| class="wikitable"
|+ Symbols
! Symbol !! Description !! Unit
|-
| <math>\Delta p</math> || pressure difference between the shaft and the outside || Pa
|-
| <math>K_\mathrm{s}</math> || coefficient, 3460 at standard atmospheric pressure || Pa·K/m
|-
| <math>T_\mathrm{o}</math> || absolute temperature of the outside air || K
|-
| <math>T_\mathrm{i}</math> || absolute temperature of the air inside the shaft || K
|-
| <math>h</math> || height above the neutral plane (negative below it) || m
|}

The relation holds at standard atmospheric pressure and requires absolute temperatures.<ref name="KL-274" /> It follows from the density difference of the two air columns. The coefficient of 3460 is close to the gravitational acceleration multiplied by the constant 353 in the book's density relation.<ref name="VR-3.2" /> For the normal stack effect, the pressure difference is positive above the neutral plane and negative below it. For the reverse stack effect, the signs are swapped.<ref name="KL-275" />

The position of the neutral plane depends on where the building leaks. If the leakage paths are spread evenly over the height, the neutral plane lies near mid-height. Where leakage is uneven, for example in shafts vented at the top, it can lie much higher or lower.<ref name="KL-275" /><ref name="KL-276" /> The pressure difference therefore grows towards the top and the bottom of the building and is largest at the ends of the shafts.<ref name="KL-275" />

=== Worked example ===
Klote considers a building 60 m tall with the neutral plane at mid-height, so 30 m above the neutral plane at the top. The outside temperature is −18 °C (255 K) and the inside temperature is 21 °C (294 K).<ref name="KL-275" /> The pressure difference is then 3460 × (1/255 − 1/294) × 30 ≈ 54 Pa. Klote gives 55 Pa from the same calculation in US units.<ref name="KL-275" /> At the top, the shaft is about 55 Pa above the outside pressure; at the bottom, it is about 55 Pa below it.<ref name="KL-275" />

For the same temperatures, the pressure difference increases by about 1.8 Pa for every metre of height from the neutral plane. A 120 m building with its neutral plane at mid-height would therefore see about 108 Pa at its top and bottom. These values are large compared with the pressures used in smoke control. Klote suggests a minimum design pressure difference of 20 to 25 Pa across a barrier next to an intense fire.<ref name="KL-285" /> Codes for pressurisation in the United States require 12.5 Pa in sprinklered and 25 Pa in unsprinklered buildings.<ref name="EV-87">Evans et al. (2005), p. 87.</ref> The buoyancy of the fire gases themselves gives about 13 Pa at 1.52 m above the neutral plane of a fire room at 800 °C.<ref name="KL-276" />

Very tall buildings reach much higher values. For the World Trade Center towers, NIST used the New York winter design temperature of −9.4 °C (15 °F). At that temperature, the stack effect pressures were of the order of 280 Pa at the bottom and top of the towers.<ref name="FS-14">Ferreira and Strege (2005), p. 14.</ref> NIST noted that this is an order of magnitude higher than the design pressure for unsprinklered buildings, so the stack effect can contribute significantly to smoke spread in tall buildings.<ref name="FS-14" /> The towers also influenced their surroundings. Under extreme weather conditions, air that entered the PATH railway tunnel in New Jersey left through the top of the towers.<ref name="FS-61">Ferreira and Strege (2005), p. 61.</ref>

== Effect on smoke movement ==
In a building with the normal stack effect, the existing air currents can move smoke far from the fire.<ref name="KL-276" /> If the fire is below the neutral plane, smoke enters the shafts with the building air and rises, helped by its own buoyancy. Above the neutral plane it flows out of the shafts into the upper floors. If there is little leakage between floors, the floors below the neutral plane, apart from the fire floor, stay relatively free of smoke for a time.<ref name="KL-276" /> If the fire is above the neutral plane, smoke is carried to the outside through openings in the facade. Where floors leak considerably, smoke also moves up to the floor above the fire.<ref name="KL-276" />

The 1993 bombing of the World Trade Center shows how strong the effect can be. The explosion cut electrical power, the ventilation systems stopped, and the outside temperature was in the twenties degrees Fahrenheit, below freezing.<ref name="FS-xxxiv" /> Openings created in lift shafts on the lower levels let smoke rise rapidly to the upper parts of the tower. NIST concluded that the stack effect could be a primary driver of rapid smoke spread in high-rise buildings, and that openings in vertical shafts strengthen it.<ref name="FS-xxxiv" /><ref name="FS-xxxv">Ferreira and Strege (2005), p. xxxv.</ref> Stair doors held open by evacuating occupants increased the airflow up the stairs.<ref name="FS-xxxv" /> On 11 September 2001, fresh air drawn up from lower floors by the chimney effect also supplied oxygen to fires deep inside the towers.<ref name="MG-52">McGrattan et al. (2005), p. 52.</ref>

The reverse stack effect tends to move relatively cool smoke downwards. Hot smoke, however, can be buoyant enough to rise even under reverse stack effect conditions.<ref name="KL-276" /> In very airtight buildings with exterior stairs, it has been observed even at low outside temperatures, because the stair was colder than the rest of the building.<ref name="KL-275" /> New York fire service procedures note that the stack effect becomes noticeable in buildings over 60 feet (about 18 m) high and grows with height. Downward flow is most likely when the outside temperature is above 90 °F (about 32 °C).<ref name="LV-I">Lawson and Vettori (2005), Appendix I.</ref> The same procedures state that wind intensifies the effect.<ref name="LV-I" />

== Stack effect and smoke control ==
A smoke control system has to work against the stack effect that exists at the moment it operates. If the outside temperature falls below the winter design temperature, the system may not perform as intended.<ref name="KL-285" /> Klote points to the 99 % and 97.5 % winter design temperatures of the ASHRAE Handbook. In a normal winter, the temperature is at or below these values for about 22 and 54 hours respectively, and extremes can be much lower.<ref name="KL-285" /> Heating systems tolerate such short cold spells because building materials respond slowly. A smoke control system has no such time lag and must cope with the full stack effect at the moment it operates.<ref name="KL-285" />

[[Stair pressurisation]] is particularly sensitive. In the World Trade Center towers, studies after 1993 found that pressurised stairs needed relief venting at the top of each stair section. Without it, the stack effect would produce unacceptable door opening forces there.<ref name="FS-xxxvi">Ferreira and Strege (2005), p. xxxvi.</ref> Mechanically exhausting the stairs reduced smoke on the top floors. However, it increased the stack effect and drew more smoke into the stairs on the lower floors.<ref name="FS-xxxvi" />

NIST's analysis of alternative smoke management systems for the towers came to similar conclusions. Stack effect had a substantial impact on zoned smoke control combined with stair pressurisation, in some cases causing airflow from the fire floor into the core.<ref name="EV-90">Evans et al. (2005), p. 90.</ref> Fan speeds would probably have to be adjusted to measured pressure differences. Sandwich pressurisation, which exhausts the fire floor and pressurises the floors around it, remained effective even with the stack effect.<ref name="KL-274" /><ref name="EV-91">Evans et al. (2005), p. 91.</ref>

Fire services also use the stack effect deliberately. New York procedures describe supplying air with portable fans into the attack stair three floors below the fire, with the doors at top and bottom closed. This pressurises the stair near the fire floor and reduces the stack effect. With the top and bottom doors open, the same fans increase the stack effect and help to remove smoke through the stair.<ref name="LV-I" /> The procedures warn that using a stair for smoke removal can draw heat and flames from the fire floor towards that stair.<ref name="LV-I" />

== Calculation methods ==
Simple cases can be calculated by hand with the relation above.<ref name="KL-274" /> The International Fire Engineering Guidelines describe the stack effect as buoyancy-induced pressure differences caused by inside and outside temperature differences, and refer to Klote and Milke for the equations.<ref name="IFEG-2.5-6">National Research Council of Canada et al. (2005), p. 2.5-6.</ref> They also list the season, wind and the stack effect among the external conditions to consider when defining fire scenarios.<ref name="IFEG-2.2-3">National Research Council of Canada et al. (2005), p. 2.2-3.</ref>

Whole buildings are analysed with smoke movement models of the [[network model]] type. They represent a building as a network of spaces or nodes, each at its own pressure and temperature. Stairs and other shafts are modelled as a vertical series of spaces, one for each floor.<ref name="IS-B82">Iqbal and Salley (2004), p. B-82.</ref> Air flows through leakage paths from high to low pressure. The inputs include the inside and outside temperatures, the flow network and the flows of the ventilation or smoke control system.<ref name="IS-B82" />

NUREG-1805 notes that these models can represent the stack effect in tall buildings during extreme temperatures. ASCOS, CONTAMW, AIRNET and ASMET are examples, and NIST used CONTAM for the World Trade Center analyses.<ref name="IS-B82" /><ref name="EV-87" /> In zone models of single spaces, the position of openings relative to the neutral plane decides whether they act as inlets or outlets. Openings high in a facade are not necessarily outlets, and an opening that spans the neutral plane can act as both.<ref name="VR-9.3a">Van Rossum (2027), §9.3 (How a zone model works).</ref>

== Limitations and misconceptions ==
The relation for the pressure difference is a simplification. In real buildings, the shape and position of openings, flow resistance, wind and mechanical ventilation all influence the pressure differences and flows.<ref name="VR-3.2" /> The neutral plane is not fixed: it moves when doors or windows open or break.<ref name="KL-275" /><ref name="KL-276" /> Wind can strengthen or weaken the effect.<ref name="LV-I" />

A common misconception is that the stack effect matters only in skyscrapers. It increases with height, but it also exists in low buildings.<ref name="KL-274" /> Another is that it always moves smoke upwards. In hot weather, or with a cold exterior stair, the flow in the shafts can run downwards.<ref name="KL-275" />

The stack effect should also not be confused with the buoyancy of the fire gases themselves. Both rest on the same physics. The stack effect is driven by the normal temperature difference between the building and the outside air.<ref name="KL-274" /> Fire buoyancy is driven by the much higher smoke temperature and weakens with distance from the fire.<ref name="KL-276" />

== See also ==
* [[Smoke and heat exhaust ventilation]]
* [[Smoke barrier]]
* [[Smoke control]]

== Notes ==
<references />

== References ==
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Ferreira, M. J., & Strege, S. M. (2005). ''Smoke management systems'' (NIST NCSTAR 1-4D). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Klote, J. H. (2002). Smoke control. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-274–4-291). National Fire Protection Association; Society of Fire Protection Engineers.
* Lawson, J. R., & Vettori, R. L. (2005). ''The emergency response operations'' (NIST NCSTAR 1-8). National Institute of Standards and Technology.
* McGrattan, K. B., Bouldin, C., & Forney, G. P. (2005). ''Computer simulation of the fires in the World Trade Center towers'' (NIST NCSTAR 1-5F). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke Control]]