NBSIR 73-277

Evaluation of a Pressurized Stairwell

Smoke Control System for a 12 Story

Apartment Building

Francis C. W. Fung

Center for Building Teclinology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

June 1973

Final Report

Prepared for Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 73-277

EVALUATION OF A PRESSURIZED STAIRWELL

SMOKE CONTROL SYSTEM FOR A 12 STORY

APARTMENT BUILDING

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

June 1973

Final Report

Prepared for Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D. C. 20410

Francis C. W. Fung

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

IMATIOWAL BUREAU OF STANDARDS, Richard W. Roberts. Director

TABLE OF CONTENTS

Page

Abstract 1

1.0 INTRODUCTION 1

2.0 CONCEPTS OF SMOKE MOVEMENT DERIVED FROM BASIC PRINCIPLES 2

2.1 Movement of Air Containing Smoke 2

2.2 Buoyancy Force 4

2.3 Estimate of Volume Outflow From a Fire 5

2.4 Pressure Force Due to Volume Outflow From a Fire 6

2.5 Pressure Force Due to Stack Effect 7

2.6 Determination of Location of Neutral Plane 8

3.0 DISCUSSION OF SMOKE SIMULATION AND SMOKE CONTROL 9

4.0 HUD OPERATION BREAKTHROUGH SMOKEPROOF STAIRWELL

REQUIREMENTS 11

4.1 Operation BREAKTHROUGH Criteria 11

4.2 Method Chosen 12

4.3 Special Conditions 13

5.0 EXPERIMENTAL PROGRAM 14

5.1 Experimental Procedure 15

5.2 Instrumentations 16

5.2.1 Flow Rate Measurements 16

5.2.2 Pressure Measurements 16

5.2.3 SF, Gas Metering 16

0

5.2.4 SF^ Analysis 17

6.0 DISCUSSION OF EXPERIMENTAL RESULTS 18

7.0 STAIRWELL PRESSURE FOR EXTENDED WEATHER CONDITIONS 19
Page

8.0 CONCLUSIONS AND RECOMMENDATIONS 21

9 . 0 ACKNOWLEDGEMENTS 23

REFERENCES 24

TABLES 26-36

FIGURES 37-48
EVALUATION OF A PRESSURIZED STAIRWELL SMOKE

CONTROL SYSTEM FOR A 12 STORY APARTMENT BUILDING

by

Francis C. W. Fung

Building Fires and Safety Division

Center for Building Technology

ABSTRACT

An NBS study to evaluate the effectiveness of a pressurized

stairwell smoke control system in a high rise apartment building

is summarized and discussed in the light of experimental results,

analysis, and computer prediction. A quantitative experimental

technique of smoke simulation and smoke movement measurement is

described, supplemented by basic physical laws necessary for

correlation with small fires, and illustrated by the results of an

actual field experiment. Experiments were conducted in a 12 story

apartment building constructed on the Operation BREAKTHROUGH

prototype site in St. Louis, Missouri. The -experimental results

are then further extended to a wider range of ambient weather

conditions by way of computer prediction calculations. General

conclusions and relevant recommendations as a result of the study

are also presented.

Key Words: Analysis; basic correlation formulas; computer

calculations; high-rise building fire; Operation BREAKTHROUGH;

pressurized stairwell; quantitative experiment; smoke control;

smoke simulation

1.0 INTRODUCTION

The many fire safety problems introduced by smoke have been widely

recognized. Traditionally, the characterization of smoke and smoke control

in building fires has been very actively investigated by the fire research community. Of late the investigations have received new impetus

due to a focus of attention on high rise building fires. Smoke as a

critical factor in high rise building fire safety has been well discussed

by a number of authors [1,2]. It is well known that the laws of nature

dictate that hot smoke and gases from a fire will move upwards. In the

case of fire in a conventional high rise building the combination of

bouyancy force due to fire and the stack effect due to weather conditions

can cause air and smoke to travel upwards in stairways, elevator shafts

and vertical utility shafts. This vertical movement of smoke not only

speeds smoke infiltration to the upper levels, it can also leave all the

escape paths smoke logged. This smoke logging of stairway and elevator

shafts presents the added hazard of obstructing fire fighting as well as

preventing safe evacuation from a building fire.

Recent research abroad and in the United States has indicated the

feasibility of smoke control by means of ventilation; and in particular

maintaining the exitways smoke free by pressurization of the stairwells.

From a brief survey of the current status of smoke control in high rise

buildings it appears that the basic principle and guidelines for this

technique of smoke control in high rise buildings have been developed

[3-10] . For a more detailed literature discussion one is referred to

Hobson and Stewart's article [11]. For general guide lines on high rise

smoke control one is referred to Galbreath, McGuire and Tamura's article

1
on control of smoke movement [12],

Current smoke control activities at the NBS are aimed at putting

the techniques to practice by providing a quantitative design base.

With this in mind two approaches have been taken: One, to conduct

high rise smoke simulation experiments that can quantitatively measure

the smoke movement under pressurized and unpressurized conditions; and

second, in conjunction with the first approach, to model the smoke

simulation experiments analytically and to establish a smoke movement

prediction computer program for optimum smoke control design and

standards

.

2.0 CONCEPTS OF SMOKE MOVEMENT DERIVED FROM BASIC PRINCIPLES

Following is a summary of useful concepts applicable to smoke movement study and control. The inclusion of certain concepts is guided by

their usefulness in practical smoke control rather than their elegance,

and to facilitate discussions on smoke simulation experiments in the

following sections. An attempt will be made to illustrate these concepts

by derivations from elementary principles. The purpose of these

derivations is to present the concepts in simple expressions to make them

available to a wider spectrum of interests in the fire community.

2.1 Movement of Air Containing Smoke

Fluid motion in general, including air or smoke, is caused by the

action of natural and mechanical forces. In a fire the two motivation

forces that cause smoke movements are buoyancy force and pressure forces.

Buoyancy forces in a fire are caused by density changes due to heating.

The relative differences in density then sets up a convective flow in a

2
gravity field. Pressure forces can originate in a number of ways, e.g.

by restriction of volume expansion, by stack effect or by the introduction of ventilation controls. Before discussing these forces,

consider smoke motion caused by a generalized pressure force, p. The

momentum equation for the flow field in this case can be simply written

as

,

pVVV = -Vp (1)

where

p: the gas density,

V: the gas velocity vector

p: the pressure distribution of the flow field

V: the gradient operator.

Integrating (1) along the direction of smoke motion one obtains

l/2pV^ = |ApI (2)

where

Ap: the pressure difference

Assume that gas density change is governed by the ideal gas law,

P=|t (3)

where

T: the absolute temperature

R: the gas constant

Combining (2) and (3) and evaluating for air under one atmosphere

condition, with R equaling 53.3 ft. lb/lb "R one obtains

m

V = 174/ApT (4)

where

V: velocity in feet per minute

3
T: Temperature in degrees Rankine

Ap: Pressure difference in inches of

2 If Ap is expressed in lb/ft we have

^

V = (5)

Equations (4) and (5) clearly shows that it takes very little pressure

difference to move air at a considerable velocity, e.g., 0.01 inch water

' 2 pressure or 0.05 lb/ft can generate velocity of 400 ft/min or 4.5 mph at

room temperature.

2.2 Buoyancy Force

Consider the bulk ambient air temperature to be T and the

corresponding density p . The buoyancy force per unit volume due to

O D locally heated air at temperature T and density p in the gravity field

is simply

,

Fg = (P^ - p)g (6)

Substituting (3) in (6) at constant pressure, one obtains,

F = £^ (i -

B R ^T T'^ o Evaluating for air at one atmosphere pressure we have,

F =40 (i -i) (7) o where

F„ is in Ib/ft"^

D Transforming to pressure difference for a given flame height H, we have

APg = 7.7 - H (8)

o where

Ap^: pressure difference due to buoyancy force in inches H2O

H: flame or hot gas column height in feet

4
The above formula shows that for a fully developed fire with gas temperature reaching 1600°F and confined to one floor with a ceiling height of

10 ft the pressure difference due to buoyancy can reach 0.1 inch H^O.

2.3 Estimate of Volume Outflow From a Fire

Consider the following simplified cellulose burning reaction in air

as representing one possible form of wood burning in a fire,

C^H^qO^ + 6 0^ + 24 N^- ^6 CO^ + 5 H^O + 24 (9)

The above reaction indicates that for every lb-mole of cellulose 30 lbmoles of air are required to sustain burning, resulting in 35 moles of total

combustion products. Knowing that one lb-mole of cellulose weighs 162 lbs

3 and one lb-mole of any gas occupies 359 ft at STP, one can calculate the

volume of combustion products per pound of cellulose consumed as follows,

359 3 1 V = TZT X 35 ft = 77.5 ft at STP (10) 162

Thus for a given burning rate R Ib/min of cellulose and a burn room

average air temperature T we have

V = 77.5 R Y- (10a)

O o We see that in a fire where temperature can reach as high as 1600 F

the effect of temperature increase can represent a five fold expansion

of gas at room temperature.

The stoichiometric reaction stated in equation 9 also indicates an

air to cellulose ratio of 5.3 to 1 by weight. This checks with Thomas'

calculation [13] that in a ventilation controlled fire the air to

fuel ratio can be estimated to be in the range of 5.45 to 1 by weight. It

may be pointed out that the roughly 5 to 1 to fuel ratio fire is a lower

5
limit estimate. More typical ratios of air to fuel appears to be

approximately 10 to 1 according to actual measurements of hot gaseous

flow from a fire in Ref. [14], An upper limit of hot gaseous flow

from a fire appears to be 20 to 1 according to experimental measurements in Ref. [15]. Thus the estimate of hot gaseous flow per pound of

burned cellulose given in equation (10) is a conservative extimate. In

a more typical fire the amount of outflow can be doubled. In general

we can write,

The hot gases generated by a room fire will expand according to

ideal gas law and be pushed out of the room through openings. In so

doing the gas will exchange heat for kinetic energy. In a fire situation

where the absolute pressure remains near one atmosphere the velocity of

the hot gases can be estimated from the burning rate and the size of

the room openings to the outside.

In section 2.3 we have estimated that for ventilation controlled

fire the volume of gaseous product per pound of burning cellulose is

77.5 ft at STP. Let R be the burning rate in pound per minute, then

O rp O rp

o o 2.4 Pressure Force Due to Volume Outflow From a Fire

3

o

V = R X 77.5 x

T A

(11)

o where

V: the average flow velocity in fpm through openings

T: the burn room temperature

T^: the ambient room temp

A: area of openings in ft

6
The pressure due to this flow rate can then be obtained from equation (4)

or (5).

Substituting (11) in equation (4) and solving for Ap , we obtain the

pressure force due to this volume outflow given by,

o -1 R 2 Ap = 2.0 X 10

^x~A^ ^ stochiometric burning

o where

Ap: pressure difference in inch H2O

T^, T: temperature in degree Rankine

oR: burning rate in Ib/min

In general for varying degree of air supply to a fire as discussed in

section 2.3, we have

o o 2.0 X 10"^ (^) < Ap < 8.0 X 10~^ (^) (12)

o o The above formula shows that the pressure difference across the outlet of

a burn room is directly proportional to the square of burning rate, and

inversely proportional to the square of the burn room outflow area. For

example in a fully developed room fire with a burning rate of 10 Ib/min

2 and 1600°F gas temperature, a 20 ft doorway opening can induce a pressure

2 difference of .0004 to .002 in H2O, whereas a 2 ft small window opening

can induce a pressure difference of .04 to 0.2 inch H2O across the window

opening

.

2.5 Pressure Force Due to Stack Effect

The well known stack effect in a high rise building is caused by the

difference in hydrostatic pressure due to two air columns at different

temperatures. Thus the pressure difference is given by

7
(p^ - p) gh

where

p^: the outside density

p: the inside density

g* the gravity constant

h: distance from neutral plane

Assuming the. ideal gas low are given in equation (3) we have

= f (f - i) h

o Considering one atmosphere condition, we can express the above as

Ap = 7.7 - h (13)

o where

h: is in ft

T: in degrees Rankine

Ap : in inches of water

The above formula indicates that for a 100 ft tall building with neutral

plane at mid height and a 70°F temperature differential, a maximum of

0.1 inch H^O pressure difference can be induced by stack effect.

2.6 Determination of Location of Neutral Plane

To calculate the pressure force due to stack effect in formula 13

one needs to determine the location of neutral plane. The stack effect

causes a circulatory motion with a transition neutral plane. The stack

effect causes a circulatory equilibrium pressure. This neutral plane

location can be easily determined by invoking the law of conservation

of mass.

8
Consider the simple case of a building with only top and bottom

openings

.

_ ./-Area, A2

Gas Density,/),

Neutral Pressure

Plane

Absolute Temp., Tq

Velocity, Vz

Gas Density, /52

Absolute Temp.,

T

Velocity, Vi^«

'I i , *^Area, A|

With variables indicated as in above sketch, by conservation of mass, we

have

,

Pl^^ = P2 A2V2 (14)

From equation 4 and equation 13 we obtain

and

^2^ AJ- (15)

Combining (14), (15) and solve for the ratio h2/h^, and assuming p2/p-j^~ 1

from small temperature difference, during each fire we have,

2 h^

2 o

(16)

This is a formula for determining the location of neutral plane when

given size of top and bottom openings, and inside and outside temperatures.

3.0 Discussion of Smoke Simulation and Smoke Control

In terms of smoke simulation and smoke control results of the

previous section can be summarized as follows:

1. To simulate a room fire in terms of gaseous outflow two additional

factors need to be considered besides heat. They are the volume outflow

and pressure difference created by a room fire. We have shown that the

rate of volume outflow can be simply related to the burning rate as

9
indicated in equation 10 and the pressure difference due to this overflow

is proportional to the square of the burning rate. Furthennore in a room

fire with the burn room door open as discussed in section 2. A the pressure

difference created by the outflow from the burn room is on the order of

.01 in H^O or less. Thus the simulation of smoke movement during early

stages of a fire by warm rather than hot smoke is relatively simple and

can now be related to a real fire in terms of volume flow and pressure

difference.

2. The pressure created by a buoyancy force due to the presence of a

layer of hot gases is proportional to the thickness of the layer. Thus

the effect of buoyancy force only makes itself felt when the vertical

height of the fire becomes extensive. From equation 8, a hot gaseous

layer 1 ft thick with an average gas temperature of 1600°F only sustains

a pressure of .01 in across it. In other words in terms of smoke

control in high rise buildings the buoyancy force created by the fire

itself is not the critical factor until the building is extensively involved in fire. However, if two stories are fully involved in fire with

a temperature of 1600°F the pressure difference due to buoyancy can be as

high as .2 inch H^O according to equation 8.

3. The pressure created by stack effect on the other hand is proportional to the height of the building. Thus in a high rise building

when there is a significant temperature difference inside and outside due

to weather, the stack effect is the major factor in smoke control even at

the early stages of a fire, e.g. from equation 13, a 10 story building

in the winter with a lOO^F temperature difference, can produce pressure

difference of .16 in H2O. The present design philosophy using pressurized10
stairwells following the Canadian example [12] is aimed at countering the

pressure difference and volume flow rate induced by the stack effect.

This calls for rather large flow rates during evacuation. However, it has

seldom been mentioned that the stack effect in a stairwell can be reduced

by the operation of the pressurization system. Since the pressurization

system circulates outside air into the stairwell, the stairwell temperature

can quickly reach equilibrium with the outside and thus reduce the stack

effect. This actually inhibits the upward movement of the smoke in the

stairwell. According to these considerations it appears to be more

relevant to design pressurization to aim at countering the buoyancy force

due to a fire. Since, the stack effect is a function of the indoor and

outdoor temperature difference it is subject to weather variations, this

is considered in Section 7.0 by means of computer simulation.

A.O HUD OPERATION BREAKTHROUGH SMOKEPROOF

STAIRWELL REQUIREMENT

4.1 Operation BREAKTHROUGH Criteria

Criteria L.4.2.9, Volume I, Operation BREAKTHROUGH Guide Criteria

recommended that one exit stairway in apartment buildings over six

stories in height be a smokeproof enclosure. The definition of

smokeproof enclosure was:

"A smokeproof stair enclosure is a stair enclosure so

designed that the movement of products of combustion,

produced by a fire occurring in any part of the building,

into the smokeproof stair enclosure, should be limited by

the use of an appropriate design method to ensure that

with the minimum winter exterior dry bulb temperature

11
(based on the ASHRAE design tables for 97-1/2 percent

probability for the geographical location of the building)

,

the atmosphere in the stair enclosure should not, during a

period of two hours, develop a contaminated atmosphere

emanating from the fire area that is more than one (1)

percent of the volume of the smokeproof stair enclosure."

Each Housing System Producer was given the choice of using any design

method he wished in meeting the criteria noted above. For guidance, one

of the three methods described in the National Research Council of

Canada's publication, "Explanatory Paper on Control of Smoke Movement in

High Buildings" [12] was suggested.

4.2 Method Chosen

For their MFHR at St. Louis, the Housing System Producer (HSP)

elected to use a modification of NRC Method III, "Pressurized Vertical

Shafts." In this method the following conditions apply:

1. The stair enclosure chosen to be the smokeproof enclosure shall

have equipment capable of providing a mechanical air supply into the

shaft at the upper end of not less than 15,000 cfra plus

a. 100 cfm for each door (having a perimeter of not more

than 20 feet) that is equipped with a tight-fitting weatherstripping

or,

b. 200 cfm for every other door (having a perimeter of not

more than 20 feet) into the stairshaft.

12
2. Each stairshaft shall have a vent at street level, opening

either directly outside or into a vestibule or corridor that has a

similar opening to outside, having an opening of not less than 0.5 square

feet for every door that opens into the stairshaft, other than doors at

street floor level, but in any case not less than 20 square feet.

3. The vent at the bottom of the stairshaft may be provided with

a window, shutter or door, which shall open automatically, unless there

is a central control facility from which the window, shutter or door may

be opened manually, and shall be designed to remain in the open position

during the fire emergency.

4. Manual or automatic operation of a fire alarm box on any floor

shall initiate the mechanical air supply to the smokeproof stair enclosure

as provided in (1) above and shall cause the window, shutter, or door to

open as provided in (3) above.

4.3 Special Conditions

For the 12-story building at St. Louis, the basic air supply to the

smokeproof stair enclosure was set at 10,000 cfm instead of the 15,000

cfm stipulated above. Also, the HSP elected to use weatherstripped doors

on the smokeproof stair enclosure thereby reducing additional air supply

needed for door leakage from 200 cfm to 100 cfm per door. As a result,

the total air supply provided by the HSP was approximately 11,200 cfm,

made up of 10,000 cfm plus 1,200 cfm for door leakage.

The air supply fan for the smokeproof stair enclosure was placed on

the roof over the stairtower. Both this fan and the automatic-opening

device on the grade-level door to the outside were connected to the

building fire alarm system. Operation of the building fire alarm system

13
starts the fan and opens the grade-level exit door.

5.0 EXPERIMENTAL PROGRAM

An experimental program to study the effectiveness of smoke control

in a stairwell by pressurization was conducted from March 23 to 28, 1973,

at a twelve story apartment building constructed under Operation BREAKTHROUGH at St. Louis, Mo. The experiment was designed to study

systematically the effect of various key variables on smoke movement

in a high rise building. Smoke was simulated by a net air flow of

1800 CFM from a room designated as the burn room. The air was mixed

with a predetermined percentage of SF, tracer gas* and heated to a

temperature 10 degrees above the corridor temperature. The range of

reference concentrations of the SF^ tracer gas** in the air from the burn

room contains from 0.3 to 10 parts per million, which is the maximum

reference concentration from each experiment. Altogether ten simulations

were tested. Table 1 lists the description of the tested configurations.

Key variables investigated include simulated fire on the second and ninth

floors, with and without stairwell pressurization, and a number of stairwell door openings. The stairwell was pressurized by a blower delivering

11,000 CFM. This flow rate resulted in a high velocity flow and high noise

level in the stairwell. Figs. 1 and 2 show the floor plans of the second

and ninth floors respectively of the 12th story building. Rooms used to

*SF^ was chosen as a tracer gas because of its electron capture property

for detection, as well as being odorless, colorless, harmless and stable.

**0SHA concentration limits of SF^ is 1000 PPM as set forth in the

Federal Register, Volume 36, No. 157, August 13, 1971.

14
simulate the burn room are indicated in the Figures. Fig. 3 shows the

location of the air supply louver at the top of the stairwell and the

vent (door) opening at the bottom of the stairwell. This door had to be

opened manually as the automatic door release was inoperative.

5.1 Experimental Procedure

Prior to the beginning of each experiment the burn room air was

preheated to a temperature of 80°F by setting of the thermostat of the

forced air heating furnace in that apartment. Air was directed from the

outdoors into the furnace inlet by means of a cardboard duct. A window

box-type fan as shown in Figs. 1 and 2 was used to draw the preheated air

from the burn room and blow it into the corridor. A cardboard mask was

installed at the hall on the same vertical plane as the fan to allow air

from the burn room to be channeled through the fan only. The measured

air flow through the fan was approximately 1800 CFM with an average

pressure of .04 in. H^O across the fan.

At time zero a lecture size bottle of SF, gas located in front of

6 the fan was turned on to continuously deliver a predetermined amount of

SF^ , to be mixed with the burn room air supply. The infiltration of

SF^ gas into the rest of the building was then traced by sampling at

4 designated floors at both the north stairwell and mid-corridor at 5-

minute intervals. The floors chosen for measurement were the second,

fifth, ninth, and eleventh. In the sampling routine, one man was stationed

in the stairwell, and another in the building to collect integrated gas

samples at the above chosen floors beginning at 5, 15 and 25 minutes after

time zero. Each vertical traverse of the building from the 11th floor

15
to the second floor took approximately 4 minutes. The gas samples collected

in ballons were then analyzed by a third man during and immediately after

each test.

- 5.2 Instrumentation

5.2.1 Flow Rate Measurements

Flow rates were determined by average velocities. Velocity

measurements were performed by using a thermo-anemometer with a low

range 100 - 500 fpm and a high range of 500 - 1200 fpm. Average

velocities were obtained by making a traverse of 9 points for square

or rectangular ducts.

5.2.2 Pressure Measurements

Static pressures were measured by a Magnehelic pressure gauge of

.01 to 1.0 in. H^O range.

•" ' • • 5.2.3 SF^ Gas Metering

In tests 3a, 3b, 4b, 5a, 7 and 8 the continuous release of

SF^ gas was metered by a ball type flow meter with a range of 1 to

3 10 ft /hr. A slight turn of the needle valve with the ball barely off

its seat results in burn room SF, concentrations varying from 3 to 10 ppm

o for different tests. Subsequent test experience showed that with this

kind of burn room concentration it takes more than four hours of purge

time before the building is cleared of SF^ for the next test. In order

to speed up the purge time between tests it was decided to run the rest

of the tests at a lower burn room concentration. Since the dispersion of

SF^ is exponential, to cut down the dispersion time by half, one needs to

drop the burn room concentration by an order of 1 ppm (1000 ppb) is quite

16
acceptable to our experimental requirement since the gas analyser sensitivity is readable at 1 ppb . This means that the relative concentration

can be measured to one part in one thousand.

A rough estimate showed that in order to bring the air supply from

the burn room fan to SF, concentration of 1000 ppb, a continuous release

D

3 of 100 cc/min or 2 ft /hr of SF^ is required. For tests 5c, 5g and

repeat of 5a and 3e another ball type flow meter of the appropriate

range was used. The flow meter was calibrated by the soap film displacement method over the measuring range.

One additional problem associated with SF^ metering was the unsteadiness of the SF^ flow for experiments 3b, 4b. Although the relative

concentration was calculated by normalizing the sample concentration by

the burn room concentration at the corresponding time, extreme unsteadiness can result in lack of reproducibility. The unsteady SF^ metering

was found to be caused by the first flow meter used. This flow meter

was operated by barely lifting the ball from its seat. The situation

was remedied by using another flow meter with a lower range operating

in the neighborhood of 100 cc/min.

5.2.4 SF^ Analysis

SF^ samples were analysed by a portable gas chromatograph having

an electron capture cell fitted with a 300 mc tritium source. The response

of the instrument to SF^ is exponential and the usable range is between 1

and 100 ppb. Dilution of samples when necessary was effected by a 10 to

1 critical orifice.

17
6.0 DISCUSSION OF EXPERIMENTAL RESULTS

In tables 2 to 11 the results of SF^ analyses for 10 tests are summarized. SF^ concentrations for each chosen floor at the specified time

Intervals are listed in ppb , and percentage concentration normalized by

the "burn room" SF concentration. Burn room gas samples were taken in

D the hall between the "burn room" and the corridor. Comparative evaluations

of smoke concentration for the different test simulations are plotted on

Figures 4 to 12:

1. Fig. 4 compares the corridor smoke concentrations at the 15 minutes

for tests 3b and Ab . The result is that stairwell pressurization in this

case not only kept smoke concentration in the stairwell below the 0.001 or

undetectable level, it also reduced the smoke level in the building

corridor significantly.

2. Fig. 5 shows smoke concentrations in the stairwell at 15 minutes.

Note that in all tests with the pressurization on, the smoke level in the

entire stairwell was either below 0.1% or undetectable whereas in case

4b with pressurization off the measured concentration at 15 minutes

ranged from 4 to 70%.

3. Figs. 6 and 7 compare smoke concentration in the corridors for

simulated fire on the second and ninth floor respectively for different

stairwell door openings.

4. In Figs. 8 and 9 the stairwell pressurization "shake down" test

results are presented for the case of simulated fire on the second floor

and the ninth floor respectively. In each case the "shake down" procedure

was to open one stairwell door at a time at two minute intervals and then

measure the SF, concentration in the stairwell at that level. Every door

6

18
after being opened remained open for the rest of the test so that a

cumulative effect of door openings was obtained. The routine started

five minutes after initiating the SF, flow in the burn room, with sample

collections proceeding from the 11th floor down to the second floor.

Using a 1% concentration as a critical cut off limit, it appears that for

a simulated fire on the second floor, the stairwell pressurization failed

after opening the 5th floor stairwell door, and for a simulated fire on

the ninth floor, failure occurred after the opening of the 9th floor

stairwell door.

5. The force required to open stairwell doors during the pressurized

mode was also measured, by means of a graduated spring scale, since the

additional force due to pressurization can be a critical design consideration. The measured force and the calculated force from pressure

measurements are plotted in Figure 10. The correlation between measured

force and calculated force appears to be good except for the 11th floor

stairwell door. The total force required to open the doors under

pressurization conditions was below 30 pounds except the 11th floor door.

For this door the measured force required is 42 pounds and the calculated

force is 34 pounds.

7.0 STAIRWELL PRESSURE FOR EXTENDED WEATHER CONDITIONS

The experimental results obtained by the smoke simulation program

confirmed the feasibility of stairwell smoke control by pressurization.

The experiments were performed only under moderate 60°F outside weather

conditions and the effect of more severe weather conditions should also

be investigated. Since direct control of ambient conditions was not

possible, an alternate indirect way to extend the investigation is through

19
computation and prediction. The computer program chosen for this purpose

was a modified numerical program originally developed by Sander and Tamura

[16]. This numerical program based on Ref. [14] calculates pressure

differences in a high rise building by taking into account the buoyancy

force, stack effect due to temperature difference, net flow due to the

air handling system, and leakage flows by empirically estimated leakage

characteristics through doors, walls, and floors.

With the leakage characteristics estimated according to Ref. [lA] , and

treating the stairwell shaft as a building with large floor leakage and

the building as a vertical shaft, as suggested by T. Kusuda of National

Bureau of Standards, a series of computer calculations were performed to

predict the pressures in the subject high rise apartment building.

" The variables investigated included simulated smoke production on

second and ninth floor levels, outside weather conditions with temperatures

15°F, 60°F, and 90°F, and different stairwell door openings. Calculated

pressure differences across stairwell doors are presented in Figs. 11

and 12 along with the measured pressure differences. Fig. 11 presents

calculations for the case where pressurization is on and all stairwell

doors closed. For all cases calculated the building temperature is

assumed to be 72°F. The pressure difference across the stairwell doors

in each case is caused by the combined effects of the pressurization

system and the temperature difference between the building and the

stairwell. Agreement of calculation for the case of 60°F outside temperature with the corresponding case 3a experimental measurement is fair.

Fig. 12 presents calculations for the case where pressurization is

on, and the second and 11th floor stairwell doors are open. Agreement of

20
the calculations for a 60°F outside temperature with the corresponding

case 3e experimental measurement is excellent. In both Figs. 11 and 12

one can see that according to the computer calculations the stairwell

pressure differences remained positive for the two building configurations

studied for both extreme temperatures of IS^F and 90°F outside air. Positive stairwell pressure difference is the necessary condition for preventing

smoke from entering the stairwell. Thus results of the computer calculation for extended temperature ranges indicate that for the more severe

condition of a second floor fire, the stairwell has favorable pressure

conditions to remain smoke free up to opening of the second and 11th

floor stairwell doors, and at both 15°F and 90°F outside temperatures,

assuming the stairwell reaches the ambient air temperature.

In relation to the computer calculations it may be relevant to point

out that in the subject high rise apartment the pressurization unit

circulates 11,000 CFM of outside air through the stairwell. Experimentally it was found that the stairwell air reached the temperature of

the outside air in less than a minute. Computer prediction results may

lead to different conclusions if the pressurization unit circulates

conditioned air, thus requiring different stairwell temperature input

to the computer program. However, in the subject high rise apartment

the proper temperature input under pressurization was that of the ambient

temperature level.

8.0 CONCLUSIONS AND RECOMMENDATIONS

Major conclusions as a result of the present study are:

1. Stairwell pressurization can be very effective in

preventing smoke from entering stairwells even with

several doors open. The effectiveness of the 11,000

21
cfm blower in this case was clearly illustrated by

this study

.

2. The simulation of smoke movement due to a fire in a

high rise building by using SF, as tracer gas mixed

b

with a warm air supply is feasible. The model can be

related to a real fire in terms of volume outflow,

heat energy output and average pressure difference

across the burn-room doorway.

3. Present smoke control design guidelines are in need

of optimization by using quantitative experiments

and computer calculations.

Relevent future recommendations as a result of the present study are

1. Smoke simulation experiments by using SF, as a tracer

b

gas mixed with heated air should be relatable to a wide

- range of early burn-room fires through basic physical

laws in terms of volume outflow, heat energy output

and average pressure across the burn-room door. Basic

formulas for this comparison are contained in

section 2 of this report.

2. Proper design of prototype smoke control systems

should consist of (a) design estimate according to

physical laws similar to those contained in section

2 of this report and (b) realistic smoke simulation

experiments with quantitative measurements such

as the SF, technique used in this program

(c) computer calculations for correlation with

experiment and to cover extended weather conditions.

22
3. The high noise level of large, high velocity

pressurization units can be an objectionable

feature even though it is designed for safety.

A possible solution for this is both optimum

design and breakdown of large pressurization

units into smaller units distributed vertically

along the stairwell.

4. As a result of the added force required to open stairwell

doors due to pressurization, it is recommended that a design

specification be required to limit the maximum force needed

to open pressurized stairwell doors.

9 . 0 ACKNOWLEDGEMENTS

The computer program used for predicting the performance of the

stairwell was developed with help from Dr. Tamami Kusuda of the National

Bureau of Standards. The field data collection was supported by a contract from the Department of Housing and Urban Development.

Messrs. James Steel, Richard Zile and Tom Lee of Building Fires

and Safety Section, National Bureau of Standards, were most helpful in

the data collection.

23
REFERENCES

1. Hutcheon, N.B., Shorter, G. W. , "Smoke Problems in High-Rlse

Buildings," ASHRAE Journal, 9, 1968.

2. Galbreath, M. , "Fire in High Buildings," National Research Council

of Canada, Fire Study No. 21, A, 1968.

3. McGuire, J. H., "Control of Smoke in Building Fires," Fire

Technology, Vol. 3 , No . 3 , 8, 1967.

4. McGuire, J. H. , "Control of Smoke in Building Fires," Fire

Technology, Vol. 3, No. 4, 11, 1967.

5. Tamura, G. T., Wilson, A. G., "Building Pressures Caused by

Chimney Action and Mechanical Ventilation," ASHRAE Transactions,

1967, Vol. 73, Part II.

6. Tamura, G. T., Wilson, A. G., "Pressure Differences Caused by

Chimney Effect in Three High Buildings," ASHRAE Transactions,

1967, Vol. 73, Part II.

7. Barrelt, R. E., Locklin, D. W. , "Computer Analysis of Stack Effect

in High-Rise Buildings," presented at ASHRAE 1968 Annual Meeting

at Lake Placid, New York, 6, 1968.

8. Butcher, E. G. , Fardell, P. J. and Clarke, J., "Pressurization

as a Means of Controlling the Movement of Smoke and Toxic Gases

on Escape Routes," Joint Fire Research Organization Symposium No. 4,

Movement of Smoke on Escape Route in Buildings, Paper 5, Watford, 1969.

9. Butcher, E. G., Hall, M., "Smoke Tests in New Law Courts Building,"

Joint Fire Research Organization Research Note No. 889, 1971.

10. "Mechanically Ventilated Smoke Proof Enclosure, "Los Angeles Fire

Department, 1970, City of Los Angeles BFP and PA Requirement No. 56.

24
11. Hobson, P. J., Stewart, L. J., "Pressurizatlon of Escape Routes in

Buildings," Heating and Ventilating Research Association, Bracknell

Berkshire, England.

12. Galbreath, M. , McGuire, J. H., Tamura , G. T., "Exploratory Paper

on Control of Sraoke Movement in High-Rise Buildings," National

Research Council of Canada, Ottawa, 6, 1970.

13. Thomas, P. H., Heselden, A. J. M., "Fully-Developed Fires in Single

Compartments," Fire Research Note No. 923, August 1972, Fire

Research Station, Joint Fire Research Organization.

14. Fung, Francis C. W. , Suchomel, M. R., Oglesby, P. L., "Corridor

Fires Energy and Radiation Models, NBS Tech. Note, Washington, D.C.,

1973.

15. Lee, B. T., Private Communication, National Bureau of Standards,

Washington, D.C. 1973.

16. Sander, D. M., Tamura, G. T., "A Fortran IV Program to Simulate

Air Movement in Multi-Storey Buildings," National Research Council

of Canada, Ottawa DBR Computer Program No. 35, March 1973.

25
Table 1 Experimental Test Configurations

Test No Simulated Fire Stairwell Stairwell

Pressurization Doors Open

3a 2nd Floor on All closed

3b 2nd Floor on 2nd Floor

3e repeat 2nd Floor "on" 2nd & 11th

4b 2nd Floor "off" 2nd Floor

5a 9th Floor IT f

* on All Closed

5a repeat 9th Floor on All Closed

5c 9th Floor on 9th & 11th

5g 9th Floor on 2nd, 9th &

7 ] For description of pressurization shake down test

8 See Section 6.0, article ^ on Page 18

26
Table 2

Test 3a, "Fire on Second Floor", Pressurization "On", all Stairwell Doors Closed

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Meter tration Normalized Meter tration Normalized

Level Dilution Reading ppb by B.R. Dilution Reading ppb by B.R.

Time

30 min

2 1:100 20-21 3377.3 1 1:1 10-8 5.2 .001

5 1:1 50-12 56.8 .017 —

9 1:1 50-13 65.1 .019 ——

N.C.*

11 1:1 50-17 85 .9 .026

Time

40 min

2 1:100 20-20 3167.1 1 1:1 10-8 .001

5 1:1 20-38 88.5 .028

9 1:1 20-40 99.8 .032 N.C.

11 1:1 50-17 85.9 .027

Time

50 min

2 1:100 20-21 3377.3 1

5 1:1 50-13 65.1 .019 N.C.

9 1:1 50-14 74.6 .022

11 1:1 20-46 156.6 .046 1:1 10-16

Time

60 min

2 1:100 20-21 3377.3 1 1:1 20-10 13.8 .004

5 1:10 20-13 186.7 .055 1:1 10-18 13.0 .004

9 1:10 20-9 123.0 .036 1:1 10-12 7-9 .002

11 1:10 1:1 10-18 13.0 .004

* N.C: No sample collected, break down of sampling procedure

Outdoor temperature: 64°F

Average Indoor Temperature: 73''F

27
Table 3

"Fire on Second Floor" Pressurization "on", Second Floor Stairwell Door

Corridor Stairwell

Concen- Ratio Concen- Ration

Floor Meter tration Normalized Meter tration Normalized

Level Dilution Reading ppb by B. R. Dilution Reading ppb by B.R.

i ime

5 min

2 1:100 20-24 4054.3 1 1:1 5-2 .6 .000

5 1:1 20-14 20.4 .005 1:1 5-4 1.3 .000

9 1:1 20-30 56.8 .014 1:1 5-0 N.D. N.D.*

11 1:1 20-21 33.8 .008 1:1 5-0 N.D . N.D.

Time

15 min

2 1:100 20-29 5378.5 1 1:1 5-1 .000

5 1:1 20-13 18.7 .004 1:1 5-3 .000

9 1:1 20-42 113.6 .021 1:1 5-8 2.5 .000

11 1:10 20-25 429.8 .080 1:1 5-13 4.5 .001

Time

25 min

2 1:100 20-36 7892.4 1 1:1 5-11 3.8 .001

5 1:1 20-23 38.2 .005 l-.l 5-3 .000

9 1:10 20-36 789.2 .100 1:1 5-6 .000

11 Lost 1:1 5-18 56.4 .001

* N.D.: Not detectable

Outdoor temperature: 55°F

Average indoor temperature: 75°F

Test 3b,

Open

r

28
Table 4

Test 3e repeat, "Fire on Second Floor", Second and Eleventh Floor Stairwell Doors Open

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Meter tration Normalized Meter tration Normalized

Level Dilution Reading ppb by B.R. Dilution Reading ppb by B.R.

Time

5 min

2 1:10 20-20 316.7* 1 1:1 2-0 N.D.

5 1:1 20-8 10.8 .034 1:1 1-0

9 1:1 10-12 7.9 .025 1:1 2-0 f T 11 1:1 2-9 1.3 .004 1:1 5-0 1 f

Time

15 min

2 1:10 20-19 296.4 1 1:1 1-0 II

5 1:1 20-9 12.3 .042 1:1 1-0 1!

9 1:1 20-8 10.8 .036 1:1 1-0 ei 11 1:1 20-9 12.3 .042 1:1 1-0 M

Time

25 min

2 1:10 20-22 359.5 1 1:1 1-0 I!

5 1:1 20-10 13.8 .039 1:1 1-0 1!

9 1:1 20-12 17.0 .047 1:1 1-0 i: 11 1:1 20-6 7.9 .022 1:1 1-0 II

N.D.: Not detectable

Outdoor temperature: 65°F

Indoor temperature: 72°F

*Ball type Flow meter setting: 4

29

1
Table 5

Test 4b, "Fire on Second Floor" Stairwell Pressurization "Off", Second Floor

Stairwell Door Open

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Meter tration Normalized Meter tration Normalized

Level Dilution Reading PPb by B.R. Dilution Reading PPb by B.R.

Time

5 min

2 1

• 1 on QQ78 1

S

1X X1 •. X1 5 1:1 10-36 27.7 .027 1:1 50-19 185.7 .185

9 1;1 20-lA 20.4 .020 1:1 5-12 3.8 .004

11 i:i 50-19 185.7 .185 1:1 5-18 5.8 .006

Time

15 min

2 1:100 20-26 4550 1 1:100 20-19 2963.8 .651

5 1:1 50-19 185.7 .041 1:100 20-20 3167.1 .696

9 1:1 20-36 78.9 .017 1:10 20-13 186.7 .041

11 1:10 20-47 1744.3 .38 1:10 20-14 203.7 .045

Time

25 min

2 1:100 20-26 4550 1 1:100 20-18 2767.0 .608

5 1:10 20-24 4054 .089 1:100 20-20 3167.1 .696

9 1:10 20-15 221.1 .049 Lost

11 1:10 20-46 1566.0 .344 1:10 10-32 239.1 .053

Outdoor temperature: 59°F

Indoor temperature: 74 °F

30
Table 6

Test 5a, "Fire on Ninth Floor" all Stairwell Doors Closed, Pressurization "On"

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Meter tration Normalized Meter tration Normalized

Level Dilution Reading ppb by B.R. Dilution Reading ppb by B.R.

Time

5 min

2 1:1 5-2 .6 .002 1:1 1-0 N.D.

5 1:1 10-22 15.4 .049 1:1 1-0 II

9 1:10 20-20 316.7* 1 1:1 1-0 II 11 1:1 5-28 9.4 .030 1:1 1-0 II

Time

15 min

2 1:1 5-2 .6 .001 1:1 1-0 II

5 1:1 10-22 15.4 .036 1:1 1-0 It

9 1:10 20-25 429.8 1 1:1 1-0 11 11 1:1 20-31 60.0 .140 1:1 1-0 II

Time

25 min

2 1:1 5-4 1.3 .003 1:1 1-0 II 5 1:1 20-14 20.4 .045 1:1 1-0 II

9 1:10 20-26 455.1 1 1:1 1-22 II 11 1.1 20-42 113.6 .25 1:1 1-0 It

N.D.: Not detectable

Outdoor temperature: 62°F

Indoor temperature: 75°F

Ball type flow meter setting: 4

31
.^;^v.ry^., -..V^'';.' ^ Table 7

Test 5a repeat, "Fire on Ninth Floor", all Stairwell Doors Closed, Pressurization "On"

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Me ter tration Normalized Meter tration Normalized

Level Dilution Reading ft"-' bv B.R. Dilution Reading ppb to B.R.

Time

5 min

2 1:1 2-2 .3 .001 1:1 1-0 N.D.

5 .1 10-21 14 .6 .057 1:1 1-0 II

9 1:10 20-17 257 .6* 1 1:1 1-0 II 11 1:1 5-16 5.2 .02 1:1 1-0 II

Time

15 min

2 1:1 1-6 .4 .001 1:1 1-0 II

5 1:1 10-26 18.7 .041 1:1 1-0 II

9 1:10 20-26 455.1 1 1:1 1-0 II 11 1:1 20-22 35.9 .079 1:1 1-0 II

Time

25 min

2 1:1 1-7 .4 .001 1:1 1-0 II

5 1:1 10-13 8.6 .021 1:1 1-0 1!

9 1:10 20-24 405.4 1 1:1 1-0 II 11 1:1 20-34 70.6 .174 1:1 1-0 II

* Ball type flow meter setting: 4 Outdoor temperature: 59°F

Indoor temperature: 75 °F

32
Table 8

Test 5c, "Fire on Ninth Floor", Pressurization "On", Ninth and Eleventh Floor Stairwell

Doors Open

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Meter tration Normalized Meter tration Normalized

Dt 1 nf- -I nn ppb uy D . x\.

US. Xu L XfJii by B.R.

Time

5 min

2 1:1 5-3 .9 1:1 1-0 N.D. N.D.

5 1:1 10-25 17.8 1:1 1-25 1.6

9 1:1 Lost 1:1 10-10 6.5

11 1:1 5-7 2.2 ::: 1:1 5-0 N.D. N.D.

Time

15 min

2 1:1 5-7 2.2 1:1 1-0 N.D. N.D.

5 1:1 10-42 33.8 1:1 1-0 ti )i

9 1:10 10-18 123.0* 1:1 1-0 II II 11 1:1 2-8 1.0 1:1 1-9 .6

Time

25 min

2 1:1 2-28 3.31 .006 1:1 1-0 N.D. N.D.

5 1:1 20-44 131.5 .244 1:1 1-0 M II

9 1:10 20-29 537.9 1 1:1 2-8 1.0 .002

11 1:1 1-0 N.D. N.D. 1:1 1-0 N.D. N.D.

T N.D.: Not detectable

Outdoor temperature: 65°F

Indoor temperature: 75°F

*Ball type flow meter setting: 4

33

I
Table 9

Test 5g, "Fire on Ninth Floor", Stairvell Pressurization "On", Second, Ninth and

Eleventh Floor Stairwell Doors Open

Corridor Stairwell

Concen- Ratio Concen- Ratio

Floor Me ter IN 1^ I. Ill du_ _L ^cu Me te r t" "ration Normalized

Level Dilution Reading Ppb by E.R. Dilution Reading ppb by B.R.

Time

5 min

2 1:1 5-5 1.6 .001 1:1 2-5 .6 .001

5 1:1 50-10 43.0 .033 1:1 2-7 .9 .001

9 1:10 20-44 1314.5* 1 1:1 2-5 .6 .001

11 1:1 5-6 1.9 .001 1:1 2-11 1.4 .001

Time

15 min

2 1:1 5-8 2,5 .002 1:1 2-9 1.2 .001

5 1:1 50-9 37.1 .035 1:1 2-5 .6 .001

9 1:10 20-41 1063.1 1 1:1 2-7 .9 .001

11 1:1 2-6 .6 .001 1:1 2-11 1.4 .001

Time

25 min

2 1:1 5-10 3.2 .002 1:1 2-12 1.5 .001

5 1:1 20-38 88.5 .062 1:1 2-8 1.0 .001

9 1:10 20-45 1427.6 1 1:1 2-10 1.3 .001

11 1:1 2-11 1.4 .001 1:1 2-8 1.0 .001

Outdoor temperature: 60°F

Indoor temperature: 74°F

*Sall type flow meter setting: 6

34
Table 10

Test 7, "Fire on Second Floor", Pressurized Stairwell "Shake Down",

Stairwell Doors Being Opened at 2 Minute Intervals, Beginning Eleventh

Floor at 5 Minute

Stairwell

Concen- Ratio

Floor Meter tration Normalized

Level Dilution Reading ppb by B.R.

2 1:100 10-12 792.6 .221

3 1:10 20-16 239.1 .067

4 1:1 20-34 70.6 .020

5 1:1 20-44 131.5 .037

6 1:1 10-14 9.4 .003

7 1:1 10-18 12.3 .003

8 1:1 10-10 6.5 .002

9 1:1 5-10 3.2 .001

10 1:1 5-10 3.2 .001

11 1:1 5-10 3.2 .001

B.R. 1:100 10-44 3594.9

Outdoor temperature: 58**F

Average indoor temperature: 72*'F

35

r
Table 11

Test 8, "Fire on Ninth Floor" Pressurized Stairwell "Shake Down",

Stairwell Doors Being Opened at 2 Minute Intervals, Beginning Eleventh

Floor at 5 Minute

Stairwell

Floor

Level Dilution

Meter

Reading

Concentration

ppb

Ratio

Normal

by B.R

. 2 1:1 10-12 7.9 .002

3 1:10 10-12 79.3 .022

4 1 :

1

50-18 142.8 .040

5 1:10 5-20 65.3 .018

6 1:1 50-16 99.8 .028

7 1:1 20-40 99.8 .028

8 1:1 20-23 38.2 .011

9 1:10 10-10 65.3 .018

10 1:1 5-10 1.4 .000

11 1:1 5-11 1.4 .000

B.R. 1:100 20-22 3595 1

Outdoor temperature: 59*'F

Average indoor temperature: 74*F

36
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I

FORM NBS-114A (1-71) f

U.S. DEPT. OF COMM. 1. PUBLICATION OK REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA No. SHEET NBSIR 73-277

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Evaluation of a Pressurized Stairwell Smoke Control System

for a 12 Story Apartment Building

5. Publication Date June iy/J

6. Performing Organization Code

7. AUTHOR(S)

Francis C. W. Fung

8. Performing Organization

NBSIR 73-277

9. PERFORMING ORGANIZATION NAME AND ADDRESS

WAllONAL BUKhAU Or blANUAKUo

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4608412

11. Contract/Grant No. IAA-H-37-72

12. Sponsoring Organization Name and Address

v/i-x-xc-c lUL rujLxcy i/cVcxoptnent anu rvesearcn Department of Housing and Urban Development

Washington, D.C. 20410

13. Type of Report & Period

Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 20C-word or less factual sunim.aty of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) An NBS Study to evaluate the effectiveness of a pressurized stairwell smoke

control system in a high rise apartment building is summarized and discussed

In the light of experimental results, analysis, and computer prediction. A

quantitative experimental technique of smoke simulation and smoke movement

measurement is described, supplemented by basic physical laws necessary for

correlation with small fires, and illustrated by the results of an actual

field experiment. Experiments were conducted in a 12 story apartment building

constructed on the Operation BREAKTHROUGH prototype site in St. Louis, Missouri.

The experimental results are then further extended to a wider range of ambient

weather conditions by way of computer prediction calculations. General con- clusions and relevant reeoinmendations as a result of the study are also

presented.

. 4 .

17, KEY WORDS (Alphabetical order, separated by semicolons)

Analysis; basic correlation formulas; computer calculations; high-rise building

fire; Operation BREAKTHROUGH; pressurized stairwell; quantitative experiment;

smnke r n nrrol ; smoke '^ttthiI at- i np

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OSCOMM-DC 66244-P71