Experimental and modeling 


investigation of the effect of ventilation 

on smoke rollback in a mine entry
 

Introduction prevent direct access to the fire, 

can leak through stoppings into a

jacent airways and thereby furthe

endanger the miners. One extrem

consequence of a further increase 

the fire intensity is that a sufficient

large heat production rate can pro

duce flow reversal in an intake airwa

if the airway connects with parall

intake airways. The parallel airway

could carry the balance of the airflo

to substantially maintain the prefir

mine pressure drop. 

The use of ventilation to contr

the movement and dilution of smok

associated with an undergroun

J.C. Edwards, r.a. Franks, 

G.F. FriEl and l. Yuan 

J.C. Edwards, member sME, R.A. Franks, G.F. Friel and L.

Yuan are research physicist, electronics engineer, chemical 

engineer and associate service fellow, respectively, with the 

national institute for Occupational safety and Health, Pittsburgh 

research laboratory, Pittsburgh, Pa. 

An underground mine fire can have 

devastating consequences for miners 

and the mine if not controlled in its 

incipient stage. Inhalation of the firegenerated toxic products of combustion 

(POC) can be injurious or fatal for miners, and the heat released can induce 

roof and rib collapses. Initially, the thermal buoyancy forces generated by the 

fire will produce an ascending plume 

of fire POC. With sufficient ventilation, 

the POC will initially be transported 

downwind from the fire. Once the fire 

has evolved to sufficient intensity, the 

buoyancy forces will overcome the inertial forces of the ventilation, and the POC will migrate 

upwind along the roof counter to the positive ventilation. 

As noted by Mitchell (1996), smoke from mine fires always rolls back in sufficiently low airflows and can contain combustible gases that are subject to ignition by the 

mine fire when diluted by air. This poses a risk for the 

firefighters. The ventilation velocity, airway dimensions, 

airway slope and fire intensity determine the extent of 

smoke rollback along the roof into the fresh air. 

Moderately small quantities of fuel can generate significant heat and smoke. A diesel fuel spill covering a 

0.93-m- (3-ft-) diameter circular area would generate a 

1-MW fire source. Similarly, a conical pile of broken coal 

with a 4.57-m- (15-ft-) diameter at the base and a height 

of 1.83 m (6-ft) would generate a 1.5 MW fire. A 2.4-m- 

(7.9-ft-) high wood crib consisting of 1.22-m- (4-ft-) long, 

0.15-m- (0.5-ft-) square timbers can generate a 3.5-MW 

fire. 

The smoke layer above the fire will simultaneously 

thicken as the rollback occurs. Not only can the smoke 

Abstract 

To determine the critical air velocity for preventing smoke 

rollback, diesel-fuel fire experiments were conducted in the 

National Institute for Occupational Safety and Health’s 

(NIOSH) Pittsburgh Research Laboratory’s Safety 

Research Coal Mine. Such information is necessary for 

preplanning and implementation of ventilation changes 

during mine fire fighting and rescue operations. The fire 

intensity varied from 50 to 300 kW depending on the fuel 

tray area.Airflow in the 2-m- (6.6-ft-) high, 2.9-m- (9.5-ft-) 

wide coal mine entry was regulated during the course of 

each experiment. The airflow was measured upwind fro

the fire as an average over the entry cross-section with a

ultrasonic airflow sensor and was recorded dynamical

with a mine monitoring system.The extent of smoke reve

sal was monitored with light-obscuration monitors, ioniz

tion smoke sensors and visual observations. Experiment

results for the critical air velocity for smoke reversal as 

function of fire intensity compared very well with mod

predictions based upon a computational fluid dynami

fire dynamics simulator. 

mine fire is recommended, but not quantified.Ventilatio

control, for example, is a recommended method (Cod

of Federal Regulations, 2002) for the control of tox

products from shop areas in metal and nonmetal mine

However, a quantified ventilation strategy is not gene

ally available for implementation. The primary reactio

is egression from the mine fire region. Even under th

best of circumstances, miners are often required to egre

through a toxic low-visibility mine atmosphere produce

by the mine fire. Similarly, any attempt to approach th

fire from the intake side for its control and suppressio

will be thwarted by low-visibility smoke conditions an

toxic fire products, principally carbon monoxide (CO

associated with smoke backlayering. 

Disclaimer: The findings and conclusions in this repor

are those of the authors and do not necessarily repre

sent the views of the National Institute for Occupationa

safety and Health. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Plan view of mine test section. 

In the absence of remote real-time ventilation and 

POC monitoring, the selection of a ventilation change is 

not without unknown risks. To meet the objective of establishing a safe procedure for ventilation induced smoke 

control, an experimental and a computational modeling 

approach was undertaken to determine the critical ventilation velocity required to prevent smoke reversal from 

fires of specific heat intensities. This information will be 

useful for preplanning and implementation of ventilation changes under emergency conditions. Experimental 

studies on smoke backlayering from a tunnel fire and 

determination of the critical velocity to prevent smoke 

backlayering were conducted in a large tunnel (Massachusetts Highway Department, 1995), with a hydraulic 

diameter of 7.75 m (25.4 ft), and in small tunnels, with 

hydraulic diameters between 0.18 and 0.40 m (0.6 and 1.3 

ft) (Wu and Baker, 2000). 

Experiments in mine-size tunnels with hydraulic diameters of 2.38 m (7.8 ft) were conducted at Buxton (Wu 

and Baker, 2000) with fire intensities greater than 200 

kW. None of these cases were conducted in a mine entry, 

which because of their rough walls introduces additional 

turbulence. This research considers fire intensities of less 

than 300 kW in a coal mine entry for an evaluation of the 

critical velocity to prevent smoke reversal. The practical 

experimental limitations of experiments for large fire 

intensities necessitates the use of a predictive computational method to extrapolate limited experimental results 

to a range of fire intensities and mine entry dimensions 

not practically achievable experimentally. 

Modeling approaches can be semi-empirical analytic models or field models that depend on a numerical 

evaluation of the Navier-Stokes equations with a computational fluid dynamics (CFD) program. Kennedy et 

al. (1996) developed a one-dimensional analytic model 

to investigate the critical ventilation velocity required to 

prevent smoke reversal. The model depends on an estimate of the Froude number to prevent smoke reversal. 

Mitchell (1996, page A-2) proposed a simple relationship 

for estimating the critical velocity for smoke rollback in 

dependent of fire intensity. Wu and 

Bakar (2000) used a field model to 

determine the dependence of the 

critical velocity on fire intensity 

for laboratory-scale tunnel fires. A 

CFD approach will also predict the 

length of the smoke backlayer for 

subcritical air velocities. The length 

of stationary smoke backlayer as a 

function of fire intensity and venti

lation velocity has been modeled by 

Hwang and Edwards (2001) with a 

CFD computer program. 

Experimental procedure 

­

The entry selected for the 

smoke-reversal experiments was 

126 m (413 ft) long, had an average height of 2.06 m (6.76 ft) and 

a width of 2.91 m (9.55 ft). The entry was formed from a right-angle 

bend with the intake portal. Figure 

1 shows a plan view of the fire location and the doors used for regulating the airflow. The 

fire was located 40 m (130 ft) downwind from the bend. 

The ratio of this 40-m (130-ft) distance to the airway hydraulic diameter was 17, which assured that the turbulent 

flow velocity was uniform. Five-point vane anemometer 

measurements made over the entry cross section at the 

fire zone indicated this to be the case. The slope of the 

airway upwind and downwind from the fire was less than 

0.2° and was, therefore, inconsequential for smoke movement along the roof. 

The fire source on the entry floor consisted of a pan 

containing diesel fuel. To control the heat-release rate, 

the fire pan surface areas ranged from 0.09 to 0.49 m2 

(1 to 5.3 sq ft) for the experiments. Monitoring of the 

smoke reversal was accomplished with two sensor stations located 3 and 9.1 m (10 and 30 ft) upwind from the 

fire source, as well as markers spaced every 1.52 m (5 ft) 

upwind from the fire along the rib for visual observation. 

At each sensor station, a light obscuration monitor was 

suspended approximately 0.5 m (1.5 ft) from the roof, 

above which was positioned an ionization smoke sensor. 

Approximately 4.6 m (15 ft) upwind from the fire source, 

near the roof and rib, was a transmitter-receiver of the 

ultrasonic airflow measurement sensor. The other transmitter-receiver was located 8.28 m (27 ft) upwind on the 

entry’s opposite rib near the floor. The acoustic airflow 

and smoke indication sensor outputs were sampled every 

two seconds by the mine monitoring system. 

Measurements 

The fire effective tray sizes are listed in Table 1 for 

each experiment. For each experiment, the tray was centered on the entry floor relative to the ribs with the longer 

side positioned transverse to the entry. In Experiments 

C, E and F, two trays were positioned adjacent to each 

other to form the effective tray area. The fire intensities 

and fuel mass fluxes were calculated from visual observation of the duration of flaming combustion for known 

fuel quantities and the physical and chemical properties 

of the diesel fuel. The diesel fuel’s mass density was 876 
 

 

 

 

nd interpolated fire intensity. 

Effective tray Fuel, Fire intensity Mass flux

L Q, kW kg/s/m2 

0.46 X 0.46 9.1 130 0.0147 

0.61 X 0.61 15.1 267 0.017 

1.07 X 0.46 20.8 304 0.0142 

0.39 X 0.23 3.8 53 0.0155 

0.79 X 0.23 7.6 102 0.0148 

0.46 X 0.39 7.6 128 0.0187 

Fire pan size a

Experiment 

size, m

a

B

C

D

e

F

 

 

 

 

 

 

 

 

 

 

 

 

 

42.31 MJ/kg. Ignition was achieved by 

first pouring a small quantity (about 200 

mL) of heptane on the diesel fuel. Prior 

to ignition, the airflow was measured with 

a vane anemometer at the fire tray. A 

five-point measurement was made at the 

airway center and corners. An average 

of these results was compared with the 

average acoustic measurement of the air 

velocity over the same time interval. For 

Experiments A, B and D the relative er

ror was less than 1.2 percent, for Experi

ment C the relative error was 4.5 percent, 

for Experiment E the relative error was 

7.2 percent and for Experiment F the relative error was 

3.6 percent. 

­

­

Figure 2 shows the responses of the light monitor 

(LIGHT) and smoke sensor (SMOKE) 3 m (10 ft) upwind from the 130-kW fire for Experiment A and shows 

the response of the ultrasonic flow measurement instrument.The LIGHT and SMOKE values are normalized by 

their prefire ambient values.Also shown are several visually observed positions of the smoke roll back marked by 

the curve labeled EVENT. The extent of the smoke rollback is noted above the EVENT curve in Figs. 2 and 3. 

The light monitor as an optical device has a faster 

response to the presence of smoke particulates and their 

clearing than the diffusion mode smoke sensor. From 9:04 

to 9:08 a.m., the smoke was in the neighborhood of the 

sensors 3 m (10 ft) upwind from the fire pan. Instability in 

the roll back of the buoyancy-generated smoke resulted 

in significant fluctuations in the light and smoke sensor 

responses. Over this time period, the ratio of the average 

signal to the signal’s standard deviation was about 44 for 

the flow sensor, with reduced ratios of 11 for the light 

monitor and 3 for the smoke sensor. This illustrates how, 

for even a relatively steady airflow, the 

fire’s fluctuating thermal effects will be 

amplified in the smoke movement. 

The ventilation velocity at the flow 

measurement device was 0.54 m/sec 

(1.8 ft/sec) when the smoke backlayer 

extended 6.1 to 9.1 m (20 to 30 ft), 0.86 

m/sec (2.8 ft/sec) when the backlayer 

extended 3 m and 1.19 m/sec (3.9 ft/ 

sec) when the smoke was maintained 

at the fire pan. These velocities are 

converted to average velocities at the 

fire pan based on the 5.27 m2 (56.7 sq 

ft) entry cross-sectional area at the 

fire pan and 6.09 m2 (65.6 sq ft) crosssectional area at the flow monitor.The 

critical airflow at the fire pan for no 

smoke reversal is, accordingly, 1.38 

m/sec (4.5 ft/sec). The restriction to 

human visibility posed by the smoke 

backlayer can be estimated from the 

output of the light obscuration moni

tor. At the reduced airflow of 0.63 m/ 

sec (2.1 ft/sec) at the fire pan from 9:00 

to 9:01:50 a.m., which is a 54 percent 

reduction in the ventilation velocity 

from its critical value, the average optical density of the smoke was 0.95 and 0.31 m-1 at the ligh

monitors 3.0 and 9.1 m (10 and 30 ft) upwind from th

fire. These optical densities correspond to visibilities 

3.7 and 11.3 m (12.1 and 37.1 ft), respectively, based o

Jin’s (1977) relationship between visibility measured rel

tive to a light-emitting sign and the optical density. For 

light-reflecting sign, the associated visibilities are 1.4 an

4.2 m (4.6 and 13.8 ft). 

Jin (1977) also notes that a minimum visibility of 3 t

5 m (10 and 16 ft) is required for fire-escaping personn

familiar with the surroundings, and a visibility of 15 t

20 m (50 to 66 ft) is required for personnel unfamilia

with the surroundings. Reliance on a cap lamp’s refle

tion from mine entry markings would be characterist

of reflection from a light reflecting sign. This shows th

visibility limitation due to a relatively small 130-kW fir

for someone familiar with the mine who, for mine escap

needs to rely on a light from a cap lamp reflecting fro

mine entry markings. 

Figure 3 shows similar results for the 304-kW fire 

Experiment C. The constant values for the measured ai

flow from 9:10 to 9:14 a.m. and from 9:28 to 9:34 a.m. ar

­

Figure 2 

Optical and smoke sensor dimensionless response at the 3-m (10-ft) station 

and airflow measurement for Experiment A. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Optical and smoke sensor response at the 3-m (10-ft) station and airflow measurement for Experiment C. 

 

 

 

Table 2 

Mine fire critical velocity, dimensionless critical velocity and fire intensity. 

Fire VC, H, 

Experiment intensity, kW m/s m Q* VC* 

a 130 1.38 2.27 0.016 0.29 

B 267 1.51 2.27 0.032 0.32 

C 304 1.55 2.21 0.038 0.33 

D 53 0.92 2.15 0.0070 0.20 

e 102 1.08 2.15 0.0135 0.23 

F 128	 1.32 2.15 0.0171 0.29 

experimental values of VC and Q. The 

dimensionless critical air velocity V * 

C

and heat release rate Q* are defined by 

(Wu and Baker, 2000) 

* V V c

c =	 (1) gH

* Q Q =

r T C gH 5 (2) 0 0 p

where 

r0 is the inlet ambient air density, 

T0 is the inlet ambient tempera

ture, 

Cp is the air specific heat (1.005 kJ/ 

kg/K) and 

g is the acceleration due to gravity 

(9.8 m/s2). 

The characteristic length H is the 

hydraulic diameter of the entry. It is 

defined as four times the ratio of the 

entry cross-sectional area to entry pe

rimeter. For Experiments C through F, 

a thermal insulating material was at

tached to the roof at the fire location 

to protect the mine monitoring system 

data transmission cables from thermal 

­

­

­

the result of very dense smoke, which causes attenuation damage.This reduction in the entry height at the fire pan 

and refraction of the ultrasonic acoustic transmissions accounts for variations shown for the hydraulic diameter, 

between the transmitter and receiver. For Experiment C, H, in Table 2.Although these dimensionless variables acthe ventilation velocity at the ultrasonic flow measure- count for the entry height and width through the hydraument device was 1.28 m/sec (4.2 ft/sec) when the smoke lic diameter, they do not account for the fire shape. 

was stabilized at the fire pan. This corresponds to a 1.55 Figure 4 shows the dependence of the dimensionless 

m/sec (5.09 ft/sec) flow velocity at the fire pan.A station- critical velocity on the dimensionless heat release rate. 

ary roof smoke backlayer of 3 m (10 ft) developed for a The literature (Thomas, 1970; Massachusetts Highway 

ventilation of 0.97 m/sec (3.18 ft/sec), as indicated by the Department, 1995) shows a dependence of Vc on Q to the 

flow measurement sensor, and a 4.3 to 4.6 m (14 to 15 ft) one-third power. The trend line in Fig. 4 shows a power 

backlayer developed for a ventilation of 0.93 m/sec (3.1 dependence equal to 0.3, which is in reasonable agreeft/sec). Table 2 lists the critical velocity, Vc

, at the fire pan ment with the theoretical one-third value.The R-squared 

to prevent smoke rollback for the six experiments. For value, the square of the coefficient of correlation, was 

the six experiments with a fire intensity range from 53 to equal to 0.89. Shown for comparison are the dimension304 kW, the ratio of the critical velocity to the velocity less values reported for the experiments of Wu and Bakar 

representative of a 3 m (10 ft) backlayer was 1.25, with a (2000), and the values they report for experiments constandard deviation of 0.1. ducted at Buxton over the comparable Q* range from 

It is instructive to represent the relationship between zero to 0.04. 

critical air velocity Vc and fire intensity Q, as dimension- The dimensionless critical velocities for the SRCM experiments are higher than the Buxton 

and the Wu and Bakar values. Both the 

SRCM and Buxton experiments used 

a tunnel with comparable hydraulic diameters. For the Buxton gallery experiments, the hydraulic diameter was 2.38 

m (7.8 ft). For the SRCM experiments, 

the hydraulic value was 2.15 m (7.05 ft) 

with thermal insulation at the roof and 

2.27 m (7.45 ft) without thermal insulation at the roof. A significant difference between the experiments was the 

arch-shaped roof of the Buxton tunnel 

and the flat roof of the SRCM entry. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

the visible flames did not fill the entry crosssection. The 

small tunnels used for the Wu and Bakar (2000) experiments had hydraulic diameters between 0.25 and 0.4 m 

(0.82 and 1.31 ft).Wall roughness is a significant factor in 

the SRCM entry, whereas the other tunnels were smooth 

walled. The fire intensities associated with the kerosene 

fires in the Buxton gallery were between 0.3 and 20 MW, 

while those for the propane source fires in the Wu and 

Bakar experiments were between 1.4 and 28 kW.Another 

factor that contributes to the difference in the experiments is the geometry of the fire source. 

Associated with smoke reversal is the roof layer’s elevated temperature, which is characteristic of the smoke’s 

buoyancy. For Experiment E, the 102-kW fire, when the 

smoke had stabilized 12.2 m (40 ft) upwind from the 

fire, the smoke temperature at the roof was 66o C (150° 

F) above the fire and was 59° and 54° C (138° and 129° 

F), respectively, 1.52 and 3 m (5 and 9.8 ft) upwind from 

the fire. For Experiment F, the 128-kW fire, when the 

smoke had stabilized 7.62 m (25 ft) upwind from the fire, 

the smoke temperature near the roof was 80o C (176° 

F) above the fire and 61° and 58o C (142° and 136° F), 

respectively, 1.52 and 5 m (5 and 16.4 ft) upwind from 

the fire.At a location 10.2 m (33.5 ft) downwind from the 

fire, the air temperature near the roof was 41oC (106°F). 

The ambient temperatures were 22° and 20o C (72° and 

68° F) for Experiments E and F, respectively. This corresponds to Thomas’s (1970) observation that reverse flow 

is associated with hot smoke and not cold smoke. This 

condition can be quantified by the Froude number, Fr, 

which is defined as 

 1− T  gh 

 Tf





(3) 

Fr = 2 V

where 

Tf is the hot gas layer temperature, 

T is the ambient temperature in (K), 

h is the tunnel height, 

g is the gravitational acceleration and 

V is the ventilation velocity. 

Application of mass and energy conservation equations with the Froude numbers equal to 4.5 by Kennedy 

et al. (1996) leads to the predicted values shown in Fig. 

4 for critical velocity. The selection of a Froude number 

equal to 4.5 was based on scale-model tests in ducts by 

Lee et al. (1979a; 1979b). The SRCM fire tests results are 

more realistically modeled with Fr = 0.75, as shown in 

Fig. 4. 

Mitchell (1996, page A-2) presents a rule-of-thumb 

for the critical velocity to prevent smoke rollback. Expressed in feet per minute (fpm), the critical velocity is 

determined by 

Vc = 100 h (4) 

where 

h is the entry height (ft). 

When converted to dimensionless units with the iden

Dimensionless critical velocity dependence on dimensionless heat release rate. 

tification of the hydraulic diameter with the entry heigh

the expression is V* = 0.29. This value is independent o

the heat release rate and is shown as a constant valu

curve in Fig. 4. For Q* values less than 0.022, the Mitche

estimate provides adequate ventilation for the preven

tion of smoke rollback for the SRCM fires. For Q* valu

greater than 0.022, the Mitchell result underestimates th

required ventilation for the prevention of smoke rollbac

A Q* value equal to 0.022 corresponds to a 135-kW fir

for an entry with a 2-m (6.6-ft) hydraulic diameter. 

Modeling 

The National Institute of Standards and Technolog

(NIST) (McGrattan et al., 2002) developed a CFD mod

of fire-driven fluid flow. NIST’S fire dynamics simulato

(FDS) is a numerical simulator for low Mach numbe

flows with special applications to heat and smoke tran

port. The program solves the Navier-Stokes equation

numerically for fluid flow with a mixture fraction com

bustion model. A significant feature of the program 

the large-scale eddy simulation (LES) method for tu

bulence. FDS was applied to a simulation of the six fir

experiments conducted in the SRCM at PRL.The dime

sions for the fuel tray and entry average cross sectio

were entered in detail. A 50-m (164-ft) length of tunn

section was used in the simulation with the fire located 3

m (100 ft) downwind from the entrance. The critical v

locity for the experiment is determined from the analys

of the airflow at the roof. When the airflow at the roo

does not extend upwind from the leading edge of the fir

source, the inlet flow is at the critical velocity. For the

computations, a 20-second time average over the last 2

seconds of a five-minute time interval was used to defin

the stationary state. These values were determined to b

close to two-minute time interval computations. Figure 

shows good agreement between the SRCM experimen

tally determined critical velocity and the CFD predi

tions with FDS. 

Although the instability of the smoke reversal made 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

difficult to define with great certainty, the extent of smoke 

reversal for different ventilation velocities, a reduction 

of the data with dimensionless variables makes the trend 

more apparent. For the smoke reversal length L achieved 

for different ventilation velocities Vin and heat release 

rates Q, a pair of dimensionless variables, X and Y, can 

be defined as 

Q X = AV 3

r (5) in 0

L gH Y = H C (6) p (Tf − T0 )

where 

Tf is the flame temperature (K). 

Figure 5 shows the parameters X and Y for the avail

able experimental data. For this evaluation, the flame 

temperature was set to 1,600K. The correlation between 

X and Y satisfies the simple relationship Y = 0.0238 ln(X) 

– 0.0479 with a R-Squared value, the square of the coefficient of correlation, equal to 0.68. The constant coefficients will change inversely with the selected flame 

temperature.The data for the six different fire intensities 

in the range 7.8 to 14.1 for L = 0 (Y = 0) is representative 

of the critical air velocity to prevent smoke reversal. 

­

Dimensionless correlation of smoke reversal length with 

fire intensity. 

It was demonstrated with fire smoke reversal experiments in the NIOSH SRCM that for a range of fire intensities between 50 and 300 kW in a 2-m- (6.6-ft-) high, 

2.9-m- (9.5-ft-) wide mine entry that the critical velocity 

for preventing the development of a smoke layer upwind 

from the fire is proportional to the fire intensity to the 

0.3 power. This is in substantial agreement with other 

researchers who posit a one-third law dependence on 

the fire intensity. 

The development of visibility obscuration 9 m (30 ft) 

upwind from a small 130-kW fire when the ventilation 

velocity was reduced by 54 percent from its critical value 

demonstrated the importance for maintaining the critical 

ventilation velocity for smoke control. For the fires considered, the results are in approximate agreement with an 

empirical result that is independent of fire intensity. CFD 

modeling of the dependence of the critical air velocity on 

fire intensity showed good qualitative agreement with 

measured values as shown in Fig. 4. 

References 

Code of Federal Regulations, 2002, “30CFR, Part 57.4761,” Office 

of the Federal Register, National Archives and Standards Administration, U.S. Government Printing Office, Washington, D.C., July 1, 2002. 

Hwang, C.C., and Edwards, J.C., 2001,“CFD modeling of smoke 

reversal,” Proceedings of the International Conference on Engineering 

Fire Protection Design, Society of Fire Protection Engineers, Bethesda, 

MD, pp. 376-387. 

Jin,T., 1977,“Visibility through fire smoke,” Journal of Fire & Flammability, Vol. 9, pp. 135-155. 

Kennedy, W.D., Gonzales, J.A., and Sanchez, J.G., 1996, “Derivation and application of the SES critical velocity equations,” ASHRAE 

Transactions: Research, Vol. 102, No.2, pp. 40-44. 

Lee, C.K., Chaiken, R.F., and Singer, J.M., 1979a, “Interaction between Duct fires and ventilation: an experimental study,” Combustion 

Science and Technology, Vol. 20, pp. 59-72. 

Lee, C.K., Hwang, C.C., Singer, J.M., and Chaiken, R.F., 1979b,“Influence of passageway fires on ventilation flows,” Second International 

Mine Ventilation Congress, Reno, NV. 

Massachusetts Highway Department, 1995,“Memorial Tunnel Fire 

Ventilation Test Program, Test Report,” Boston, MA. 

McGrattan, K.B., Forney, G.P., Prasad, K., Floyd, J.E., and Hostikka, 

S., 2002,“Fire Dynamics Simulator (Version3)-User’s Guide,” U.S. Dept. 

of Commerce, National Institute of Standards and Technology. 

Mitchell, D.W, 1996, Mine Fires Prevention, Detection, Fighting, 

Intertec Publishing Inc, Chicago, IL, pp.19-20 

Thomas, P.H., 1970, “Movement of smoke in horizontal corridors 

against an airflow,” Inst. Fire Engrs. Q., Vol. 30, pp. 45-53. 

Wu, Y., and. Bakar, M.Z.A., 2000, “Control of Smoke flow in tunnel fires using longitudinal ventilation systems—A study of the critical 

velocity,” Fire Safety Journal, Vol. 35, pp. 363-390.