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NBSIR 80-1984

Static Pressures Produced by

Room Fires

J. B. Fang

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U S. Department of Commerce

Washington, D.C. 20234

February 1980

Interim Report

Issued March 1 980

Prepared for: Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

i 80-1984

HOV ? 4 1980

NBSIR 80-1984

STATIC PRESSURES PRODUCED BY

J. B. Fang

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, D.C. 20234

February 1980

Interim Report

Issued March 1980

Prepared for: Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges. Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technoiogy

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ROOM FIRES 2b - im

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TABLE OF CONTENTS

Page

LIST OF FIGURES iv

LIST OF TABLES iv

Abstract 1

1. INTRODUCTION 2

2. EXPERIMENTAL DETAILS ... 3

2.1 Test Compartment 3

2.2 Instrumentation 4

2.3 Interior Furnishings and Finish Materials 5

2.4 Test Procedure 6

3. RESULTS AND DISCUSSION 6

4. CONCLUSIONS 13

5. ACKNOWLEDGEMENTS 13

6. REFERENCES 14

iii
LIST OF FIGURES

Page

Figure 1. Plan view of the test room showing locations of

furniture and wall linings, and arrangement of

instrumentation 17

Figure 2. Time history of the differential static pressures

measured at various heights in the front corner during test 5 18

Figure 3. Comparison plot of the time variations of the

pressure differentials measured at the same heights

in the front and the rear corners during test 5 . . . . 19

Figure 4. Time history of static pressures developed in various

room fire tests 20

Figure 5. Vertical distributions of the pressure differential

at various times for test 5 21

Figure 6. Vertical temperature profiles of air in the room and in

the doorway at various times for test 5 22

Figure 7. Comparison of measured and calculated air velocities at

the doorway in test 5 23

Figure 8. Relationship between the normalized pressure

differentials and average upper gas temperature .... 24

Figure 9. The normalized neutral plane and thermal discontinuity

heights as a function of average upper gas

temperature 25

Figure 10. Comparison of measured and calculated inflow and

outflow mass flow rates as a function of average upper

gas temperature in test 5 26

LIST OF TABLES

Page

Table 1. Mass flow rates for test 5 16
STATIC PRESSURES PRODUCED BY ROOM FIRES

J. B . Fang

Abstract

The distributions and time-varying nature of

the static pressures developed due to fires in

residential recreation rooms were determined for a range of combustible load densities and different

types of interior lining materials. The vertical

pressure differentials with respect to the ambient

static pressure for various fire sizes are satisfactorily correlated by a hydrostatic perfect gas model

based on temperature measurements in enclosures and an orifice flow model, and the calculated doorway inflow

and outflow gas velocities are in good agreement with

the measured values. The pressure differentials are found to reflect the locations of the neutral plane

at the doorway and the thermal discontinuity within

the fire room reasonably well, and their magnitudes

depend on the average upper gas temperature. Rates

of mass flow in and out of the room calculated from

the ceiling and the floor pressure differentials agree

fairly well with those derived from the doorway gas

velocity data.

Key words: Building fires; fire tests; flow measurement

furniture; interior finishes; residential buildings;

room fires; static pressure.

1
1. INTRODUCTION

Induced flows of cold air in and hot gas out of a fire compartment occur due to pressure differentials between the compartment and its

adjacent area. This mechanism is caused by buoyancy due to the increase

in gas temperature, and thermal expansion of the gases in the compartment.

It has been found that a temperature distribution described as a step

function provides a reasonable first approximation to the vertical

temperature profile in the compartment. Within the compartment, there

is an upward flow from the cold layer below the thermal discontinuity

interface to the hot layer as air entrained into the fire plume and

combustion products is carried upward.

Mathematical analysis of the flow through an opening using a hydraulics-orifice flow analogy has been reasonably successful for calculation of fire induced flow in enclosures [1-4]^. Recently, McCaffrey

and Rockett [5] have presented some results of static pressures developed

in full-scale and reduced size enclosures with various heat input rates

of gas burners and a comparison of experimental observations with the

hydraulics-orifice enclosure model [1,3]. However, no extensive static

pressure data are available in published reports relating to the burning

of furniture in a room and extended fire durations including both growth

and decay periods.

The fire resistance of building construction has generally been

evaluated by directly exposing the structural elements to fire conditions

in a test furnace according to the ASTM E 119 test method [6]. The level

of the static pressure to be maintained in the furnace, although not

rigorously prescribed, is one of the important factors affecting the

fire endurance rating of the test specimen involved, especially doors and

floor/ceiling constructions. This is because the convective heat transfer

at the test assembly due to outflow of hot furnace gas or inflow of cool

air and through openings and porous materials is dependent on the pressure

^Numbers in brackets refer to the literature references listed at the

end of this report.

2
difference across the assembly. Information on the static pressures

developed within a building compartment is needed as a basis for devising

rational procedures for testing the fire response of building materials

and structures.

The current basement recreation room fire stu.'.'y progiam at NBS is

aimed at developing a meaningful test procedure for evaluating the structural fire performance of floor assemblies in residential occupancies and

to suggest improved performance criteria and design procedures for the

proper selection and use of unprotected and fire protective, load bearing

structural elements. The immediate objectives of this phase of the room

fire program are to characterize basement fires based on a range of typical

fire load densities, room sizes, interior finishes and ventilation conditions and to develop a rational fire exposure curve applicable to

residential constructions.

This paper is a report of part of the work in progress. Presented

here are some measurements of static pressures and temperature levels

obtained from fires in rooms lined with selected interior finish materials

and furnished with combustible contents commonly found in residential

recreation rooms. The data include the time history of the pressure

differentials at different locations in the fire room, the vertical

distributions of pressure difference for various fire sizes, and the

relationships with the upper gas temperature inside the room and the

exhaust gas and incoming air velocities at the door opening.

2. EXPERIMENTAL DETAILS

2.1 Test Compartment

All room burnout tests were conducted in a 3.2 x 3.2 m (10.5 x 10.5 ft)

burn room with 2.4 m (8 ft) ceiling height. A doorway opening measuring

0.8 m (32 in) wide by 2 m (80 in) high located symmetrically in the front

wall was the single source of ventilation for the room. The room had one

heat resistant glass window, 0.41 m (16 in) wide by 0.2 m (8 in) high, in

3
one of the side walls for observation purposes. The basic construction

of the room was 0.2 m (8 in) thick standard lightweight aggregate concrete

block walls, concrete floor, and 1.3 cm (1/2 in) mineral board covered with

1.6 cm (5/8 in) Type X gypsum wallboard ceiling mounted to W6 x 12 steel

I-beams resting on the top of the block walls. The entire burn room was

built within a large test facility building in which the indoor air was

conditioned within the human comfort range (air temperature 21 + 4°C and

relative humidity 42 + 8%)

2.2 Instrumentation

Static pressures at various locations in the fire room were measured

by means of 0.64 cm (1/4 in) steel pipes installed horizontally through one

of the side walls with the open end flush with the exposed surface of the

wall lining panels. These pressure taps were placed at two stations—one near the door-wall corner at a horizontal distance of 0.3 m (12 in) from

the front block wall and at heights of 0.18, 0.99, 1.55, 2.01 and 2.21 m

(7, 39, 60, 79, and 87 in) above the floor, and the other station near the rear corner at a spacing of 0.3 m (12 in) from the back block wall at

heights of 0.18 and 2.21 m (7 and 87 in) above the floor. A plan view of

the test room showing the locations of pressure probes, thermocouple "trees"

and bidirectional velocity probes, and arrangements of furniture and interior finishes is given in figure 1. The pipes were connected by copper and

tygon tubing through a 12 position fluid wafer selector switch to a variable

capacitance pressure transducer, except for the top pressure tap in the

front corner which was continuously monitored by a separate pressure transducer. This pressure meter in conjunction with the fluid switch converted

the multiple differential pressures to electrical signals by time sharing

at a rate of 2 seconds per probe. Each of the two pressure transducers had

one pressure tap positioned at floor level and opened to draft-free ambient

air for a common reference. Two potentiometric strip chart recorders were

used to monitor the outputs of these transducers.

The temperature levels of the room gas were measured by bare beaded

thermocouples having a spherical junction diameter of approximately 1.5 mm

4
(0.06 in) and made from 0.5 mm (0.020 in) diameter Type K wire. A total of

47 thermocouples were distributed within nine evenly spaced thermocouple

"trees" inside the test room, and 12 thermocouples were positioned along the

vertical center line of the doorway opening. The vertical distribution of

the gas velocities at the doorway was measured by six bidirectional flow

probes [7] along with variable reluctance pressure transducers. A digital

data acquisition system was employed to record, every 8 seconds, the output

signals from the thermocouples and the velocity probes directly on a magnetic tape. The data were processed, tabulated and plotted by the

computer

.

2.3 Interior Furnishings and Finish Materials

For most of the room burnout tests, the interior furnishings included

a sofa, an upholstered chair and ottoman, an end table, a coffee table

and a bookcase. Included among the furnishings were old record files

placed in the bookcase and distributed randomly on the tops of the ottoman

and the coffee and end tables. The loading density of the combustible

contents, excluding carpeting, ranged from 15 to 37 kg/m^ (3.1 to 7.6

Ib/ft^) with a mean value of 23 kg/m^ (4.7 Ib/ft^) of the floor area,

which is an average value for an occupied recreation room in the basement

of a single family home in the Washington, D.C. metropolitan area [8].

The interior surfaces of the block walls were either painted or covered by nailing plywood panel, or gypsum board to wood furring strips

anchored to the block walls. The following table lists the wall materials

and fire load density, which is defined as the weight of combustible

materials per unit floor area:

Fire load density (ks/m^) Test no. Wall materials Interior finish Combustible contents Carpet Total

2 Painted concrete block 0 23 2.0 25

4 4 mm lauan plywood 12 15 2.0 39

5 4 nun lauan plywood 12 37 2.1 51.1

6 12.7 Iran painted

gypsum board 6 23 2.1 31.1

8 4 mm lauan plywood 12 23 2.2 37.2

5
It may be noted that the test numbers are not in sequence as there were

other fire tests with forced ventilation or closed door which are not

included in this comparison. Except for test 8, which had suspended

12.7 mm fiberboard base acoustic tile on the ceiling, the ceiling lining

used was 16 mm thick Type X gypsum wallboard over the concrete floor.

2.4 Test Procedure

A section of a daily newspaper weighing 400 g placed along the

backrest and the seat cushions in the middle of the sofa was used as the

ignition source. The paper was conditioned to equilibrium at an ambient

temperature of 23 + 3°C and a relative humidity of 50 + 5% prior to the

fire test. The test was started by igniting the newspaper with an electrically heated book of paper matches. Visual observations, video

tape and photographic records of the progress of the room fires were made

during the course of the tests. Data were generally collected for a period

of an hour, although the durations for tests 2 and 4 were shortened to

avoid damage to the surrounding structures.

3. RESULTS AND DISCUSSION

The histories of fire development in these five tests were found to

be similar in many respects, based on visual observation and data from

temperature measurements; newspaper ignited, sofa ignited in 0.8 to

1.2 min, flames extending to the ceiling in 1.2 to 1.9 min,’ other furniture

items and all combustible Interior finishes ignited (flashover) in 2.3 to

2.8 min and flames emerging from the doorway in 2.4 to 2.7 min. Typical

time variations of differential static pressures measured at various

heights in the front corner of the fire room for test 5 are given in

figure 2. The experimental points shown were the mean values obtained

from averaging the readings of pressure transducers in a finite time

interval. The differential pressure at each height is the pressure

difference between the room and the ambient pressures at that height.

As shown in the figure, the pressure differential at the top of the room

6
increased rapidly to its peak level soon after room flashover and then

decreased gradually with time in the later stages of the fire. The

maximum pressure differentials at the lower elevations were attained

more slowly.

In order to determine any variation due to the location of the

measuring station, a comparison plot of the pressure differentials as a function of time for measurements taken at the identical heights in both

the front and the rear corners is shown in figure 3. It can be seen that

there is little difference between the static pressures measured at these

two locations.

Figure 4 shows the static pressures developed within the fire room

as a function of time for four test runs. The pressure measurements were

made at two locations, 0.18 and 2.21 m above the floor and 0.305 m out

from the back wall. As shown in the figure, all of the room fires have

similar static pressure-time curves, especially in the lower cold air

region. The pressure difference developed in the hot and cold gas zones depend upon the upper gas temperature.

On the basis of the two-fluid zone model in which the gas in a compartment is assumed to be ideal and stably stratified with a region

of hot gas above and cool ambient air below, the pressure difference with

respect to ambient static pressure at a given height Z in the upper portion

of the room can be expressed by

where and T^ are the density and absolute temperature of ambient air,

g is acceleration of gravity, T is absolute temperature of the gas in the

upper part of the room, is the height of the neutral plane and H is

the room height. The height of the neutral plane can be experimentally

determined when the pressure differentials are plotted as a function of

height, or predicted with the use of equation (1) along with the data on

( 1 )

7
the upper gas temperature and static pressure measured at a certain height.

The latter method was used for calculating some of the data points shown

in figures 9 and 10.

The pressure differential with respect to ambient pressure in the

lower cold fluid zone is given by the hydrostatic relation

where is the height of thermal discontinuity.

Figure 5 shows vertical distributions of the pressure difference

with respect to the ambient pressure at that height for various times in

test 5. The figure indicates that the pressure differential in the upper

part of the fire room varies linearly with the height, and the pressure

points fall along the best-fit line as indicated in equation (1) . The

upper room gas temperature calculated using equation (1) along with the

measured value for the slope of the fitted line at times of 6.2, 31 and

42 minutes after the start of the test was found to be 751°C, 584°C and

respectively, which were comparable to the measured values of 749°C,

634 °C, and 510“C derived from averaging the readings of 36 equally spaced

thermocouples in the upper half of the room. For this test run, the

ambient air was at 21“C. As illustrated in the pressure plot, the slope

of the line fitted through the upper pressure points tends to increase

slightly with a decrease in the average upper gas temperature.

In figure 6, vertical temperature traverses of air within the room

and in the doorway are shown at the same times as those given in figure 5.

No radiation correction was made for thermocouple readings. It can be

noted that, due to turbulent mixing of both the hot gas with the cool air

entering through the doorway and mass injection from the decomposing

plywood walls and burning of debris on the floor, and radiant heating from

the hot gas layer, the temperature of the air in the lower space was significantly higher than that of ambient air and the Interface of the hot

0 < Z < Z.D

( 2 )

8
and cold layers had an increased thickness. The heights of the neutral

plane for various fire intensities shown in figure 5 were found to be

0.74, 0.93 and 1.03 m respectively, or approximately 15 percent higher

than those interpolated from the doorxs'ay temperature data. The intercept

of the upper hydrostatic line and the vertical line through the lower

pressure point in figure 5 or the use of equation i.:) together with the

value for the neutral plane yielded an estimate of the thermal discontinuity

height. The interface of these hot and cold layers was estimated to be

situated at 0.3, 0.4 and 0.45 m above the floor, respectively, at 6.2,

31 and 42 minutes. Except for an intense fire at G.2 minutes when the

hot smoky gas layer was observed to descend to the fxoor level, the heights

of the thermal discontinuity estimated from pressure data were generally

lower than those derived from the vertical gas temperature profiles.

In order to determine the relationship between the vertical distribution of static pressure developed in the fire room and the flow pattern of

air interchange at the doorway, air velocities calculated from the pressure

data shown in figure 5 were plotted in comparison with the measured center

line velocities in figure 7. The velocity for a given height was defined

as Cj^n/ 2 (Ap)/p'^ in which is an equivalent orifice coefficient [1,4],

and the gas density was evaluated using air at a temperature equal to the

average of the local temperatures of air in the doorway and within the

room at the same height. The average air temperature was used in order to

account for change in both gas density and velocity along the flow path

within the room and discharging through the doorway opening. An orifice

coefficient equal to unity was employed for calculating doorway air velocities shown in figure 7. It can be seen that the calculated velocities

are in good agreement with the measured ones in the magnitude and flow

direction. The neutral plane height estimated from the measured velocity

reversal for the fire at 6.2, 31 and 42 minutes was 0.66, 0.88 and 0.98 m,

which were found to range from 5 percent to 11 percent lower than those

interpolated by the pressure differentials as illustrated in figure 5.

9
The mass flow rates of the outgoing gases and the incoming air were

determined using both the measured and the pressure calculated velocities

along with the local gas density and cross-sectional area of the doorway

opening with an assumption of uniform flow across the door width. A

comparison of the measured mass flow rates based on doorway velocity

measurements shown in figure 7, and the calculated mass flow for fire

intensities at 6.2, 31 and 42 minutes after initiation of test 5, is

presented in table 1. The discrepancy between the mass flow rates by room static pressure measurements and those obtained from velocity data

was found to vary from 3 percent high to 20 percent low with a mean of

approximately 9 percent. For ventilation controlled compartment fires,

the steady-state burning rate of wood fuel is determined by the air supply

and can be related to the size of the opening by the approximate relation

[9,10] : m = k A V H ' where A and H are the area and the height of the

o o o o

I opening, respectively, and k is a constant about 0.092 to 0.1 kgs“^m“^/^.

For conditions employed, and assuming a negligible rate of mass accumulation within the fire room compared with the inflows and outflows, the rate

of burning was estimated to be the order of m = 0.092 x 1.55 xV2.03 =

0.2 kg/s. From the measured inflow rates given in the table, the burning

rate of ventilation controlled fires at times of 6.2, 31 and 42 minutes

was approximately equal to 0.10, 0.20 and 0.24 kg/s using a stoichiometric

air-fuel mass ratio of 5.1 kg air /kg fuel. The mass balance results also

suggest that a significant amount of fuel volatiles leaving the fire room

remained unburned, and its outflow rate decreased with increasing time.

Figure 8 shows a plot of the normalized pressure differentials with

respect to ambient density and doorway height, at the ceiling and the

floor levels in the rear corner throughout the test duration for tests 5

and 6 as a function of a dimensionless temperature (the ratio of the

temperature difference between the upper gas and the ambient air to the

average upper gas) . The absolute ambient temperatures for tests 5 and 6 were 294 K and 295 K, respectively. It can be seen from the figure that the

pressure differentials increased with an increase in the upper gas temperature. Inspection of equations (1) and (2) would lead to the conclusion

that the slopes of the best-fit lines drawn separately through the upper

10
and the lower pressure points on the plot of the normalized pressure

differentials versus the term (1 - T /T) were constant for the fixed

o heights of the neutral plane and thermal discontinuity. As shown in

figure 8, the departure from linearity demonstrates a significant variation

of the neutral plane and thermal discontinuity heights throughout the test

duration since these heights are indeed a function of room gas temperature.

However, some aspect of the data points in figure 8 are a result of the

two layer thermal approximation.

The thermal discontinuity and neutral plane heights both calculated

with the use of equations (1) and (2), respectively, and normalized to the

doorway height are displayed as a function of average upper gas temperature

for tests 5 and 6 in figure 9. The neutral plane heights interpolated

from the intersection plane between the two measured horizontal velocity

profiles of the inflows and outflows at the doorway opening for test 3 are also plotted on the same figure for comparison. It can be seen that

there is considerable dispersion of data points probably caused by the

turbulent and fluctuating nature of room fires. Yet, a general trend can

be derived from these data such that the majority of data points fall

somewhere around their best-fit lines, and suggests that positions of both

neutral plane and thermal discontinuity drop with an increase in the

spatially averaged temperature of the hot gas in the upper portion of the

fire room. Also, the calculated neutral plane heights are in reasonably

good agreement with those determined from the measured velocity reversal.

Extrapolation of the thermal discontinuity curve to allow its height to

approach zero results in an upper gas temperature of about 1030°C and at

this same time, it was observed for these tests that the entire rooms were

fully involved in flames. The corresponding room gas temperature at this

time for tests 5 and 6 were 937°C and 965°C, respectively.

The hydraulic-orifice approach has been used with reasonable success

in determining the gross features of the transport phenomena of hot-cold

fluids at the opening of an enclosure. From reference [1], the mass flow

rates of gases in and out of the fire room can be expressed in terms of

11
the neutral plane and thermal discontinuity heights, and the average upper

gas temperature, as follows:

where m^ and m^ are the mass flow rates of gases entering and leaving the

room, respectively. Figure 10 shows a plot of the rates of mass flow in

and out, which were calculated using equations (3) and (4) along with the

derived neutral plane and thermal discontinuity heights from simultaneous

measurements of the ceiling and the floor pressure differentials and

normalized by the ventilation parameter p^A^/gHj, as a function of the

term (1 -T^/T) . The flow rates obtained from the doorway gas velocity

and temperature measurements were also plotted in the same figure for

comparison. The values of the equivalent orifice coefficient used for

taking account of constriction energy loss were equal to 0.51 for air

inflow and unity for gas outflow, which provided the least deviation from

the experimental values on mass flow rates. Both sets of data indicate

that the rates of gas outflow are significantly greater than those of

air inflow especially at higher temperatures. The measured values of

m/(p^A^/gH^) for the incoming air and the exiting gas averaged over a period from room flashover to test termination were found to be 0.112 and

0.185, respectively, or m^ = 0.93 and m^ = 1.53 kg/s. In general, the

deviation of mass flow rates computed from the ceiling and the floor

pressure results from those derived from the doorway gas velocity data

was estimated to be within approximately 18 percent and 14 percent for

the Inflow and outflow, respectively.

12
4. CONCLUSIONS

Vertical profiles of the pressure differentials with respect to

ambient static pressure are found to follow the hydrostatic distribution

described by a two-layer hot and cold fluid model. Both neutral plane

and thermal discontinuity heights computed from pressure measurements at

the ceiling and the floor levels agree fairly well with those derived

from gas velocity and temperature data.

Static pressure differentials increase with an increase in the

temperature of the hot gas in the upper part of the fire room (or severity

of room fires involved) . The calculated rates of mass inflow and outflow

based on the ceiling and the floor static pressure differentials appear

to be reasonably consistent with the experimental observations of the

doorway flow.

The highest pressure difference obtained in these fire tests was

15.5 Pa (0.062 in of water) which occurred near the ceiling shortly after room flashover was found to be a factor of 2 greater than the differential

pressures developed in a room with a 450 kW gas burner [5]. This difference decreased slowly during the course of the tests due to the reduction

in burning rate within the room.

5. ACKNOWLEDGEMENTS

The fire tests reported here were the results of a team effort by

members of the Fire Safety Engineering Division. The author wishes to

thank Messrs. Thomas Maher, Oscar Owens, Ben Ramey, Charles Veirtz and

William Bailey for the construction of the test rooms and valuable assistance during the fire experiments; Mr. Sam Steel for the installation of

the instrumentation and the data acquisition system; Mr. Roy Lindauer for

the fabrication of weighing devices; Messrs. Newton Breese and Dan Debold

for reduction of test data; and Mr. Douglas Walton for the preparation of

the graphs.

13
This work is a portion of a project being sponsored by the U.S.

Department of Housing and Urban Development.

6. REFERENCES

[1] Rockett, J. A., Fire Induced Gas Flow in an Enclosure, Combustion

Science and Technology, 12, 165 (1976).

[2] Prahl, J. and Emmons, H. W. , Fire Induced Flow Through an Opening,

Combustion and Flame, ^5, 369 (1975)

[3] Quintiere, J. G., The Growth of Fire in Building Compartments,

ASTM-NBS Symposium on Fire Standards and Safety, National Bureau

of Standards, Gaithersburg, Md., April 5-6, 1976.

[4] Quintiere, J. G. and DenBraven, K. , Some theoretical aspects of

fire induced flows through doorways in a room-corridor scale model,

Nat. Bur. Stand (U.S), NBSIR 78-1512 (October 1978).

[5] McCaffrey, B. J, and Rockett, J. A., Static pressure measurements

of enclosure fires, Nat, Bur. Stand. (U.S.), J. of Research, 82 , 107 (1977).

[6] Standard Methods of Fire Tests of Building Construction and

Materials, Designation E 119, 1976 Annual Book of ASTM Standards.

[7] McCaffrey, B. J. and Heskestad, G., A Robust Bidirectional LowVelocity Probe for Flame and Fire Application, Combustion and Flame,

125 (1976).

[8] Issen, L. A., A fire and live load survey in single family and

mobile homes in metropolitan Washington, D.C., Nat. Bur. Stand.

(U.S.), NBSIR in preparation.

14
[9] Kawagoe, K. , Fire Behavior in Rooms, Building Research Institute

Report No. 27, Tokyo, Japan (1958).

[10] Heselden, A. J. M. , Thomas, P. H. and Law, M. , Burning Rate of

Ventilation Controlled Fires in Compartments, Fire Technology,

123 (1970).

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measured

at

the

same

heights

in

the

front

and

the

rear

corners

durin

test

5
20.00

(d31VM 30 MONO 3dnSS3dd OIIVIS

ooooooooo qqqqqqqqo <^00000

q q q q q

CS Th <D 06 d

o p o o o

q q q q q

04 d od d

(snvosvd) 3dnss3ad oiivis

20

Figure

4.

Time

history

of

static

pressures

developed

in

various

room

fire

tests
u

I M I I I -5 0 5 10 15

AP=P“Pgni|j (Pascals)

Figure 5. Vertical distributions of the pressure differential

at various times for test 5 21
T oo

o

CM

CO CM

CM CM

|ui| 1H9I3H

22

Figure

6.

Vertical

temperature

profiles

of

air

in

the

room

and

in

the

doorway

at

various

times

for

test

5
HEIGHT

|m|

AIR VELOCITY |m/sj

Figure 7. Comparison of measured and calculated air velocities

at the doorway in test 5 23

10
^P/PqS

Hgl

(dimensionlessl

T T

(1-Tq/T) (dimensionless)

Figure 8. Relationship between the normalized pressure differentials

and average upper gas temperature

24
Zfi/Ho

OR

Zq/Ho

(dimensionless)

Figure 9. The normalized neutral plane and thermal discontinuity

heights as a function of average upper gas temperature

25
i'/l^oAoViHol

Idimensionlessj

T T T

0.2

o INFLOW

O OUTFLOW

SOLID • Calculated from Eqs. 3 and 4

OPEN • Derived from velocity measurements

t

0.1

1

0

0.2 0.4 0.6

(1-Tq/T) (dimensionless)

0.8

Figure 10. Comparison of measured and calculated inflow and outflow

mass flow rates as a function of average upper gas

temperature in test 5 26
NBS-114A (REV. 0-78)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 80-1984J. R«cifitfi}t»'$Acd:«$5lonNo.

4. TITLE AND SUBTITLE

Static Pressures Produced by Room Fires

5. Publication Date February 1980

f. PwfUffl^Orsiiniza^n Cod«

7. AUTHOR(S) 8. Performing Organ. Report No. J . B . Fang

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

Ift. Pn>lt^^/9l0A tinit tbL

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS rsfreet, City, sute. ZIP)

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C, 20410

13. Type of Report & Period Covered Interim

14. S)»nsofing Agency Ckide

15. SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200^word or leas factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.) The distributions and time-varying nature of the static pressures developed due to

fires in residential recreation rooms were determined for a range of combustible load

densities and different types of interior lining materials. The vertical pressure

differentials with respect to the ambient static pressure for various fire sizes are satisfactorily correlated by a hydrostatic perfect gas model based on temperature

measurements in enclosures and an orifice flow model, and the calculated doorway inflow

and outflow gas velocities are in good agreement with the measured values. The

pressure differentials are found to reflect the locations of the neutral plane at the

doorway and the thermal discontinuity within the fire room reasonably well, and their

magnitudes depend on the average upper gas temperature. Rates of mass flow in and out

of the room calculated from the ceiling and the floor pressure differentials agree

fairly well with those derived from the doorway gas velocity data.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Building fires; fire tests; flow measurement; furniture; interior finishes; residential

buildings; room fires; static pressure.

18. AVAILABILITY rXl Unlimited

I I For Official Distribution. Do Not Release to NTIS

I I Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

rXI Order From National Technical Information Service (NTIS), Springfield, 22161

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22. Price

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