NBSIR 77-1209

Control of Smoke Movement in

Buildings: A Review

I. A. Benjamin, F. Fung and L. Roth

Center for Fire F

Institute for App

National Bureau

Washington, D.

July 1977

Final Report

Benjamin, I. A., Fung, F, Roth, L. , Control of smoke

movement in buildings: A literature survey,

Proc. 2nd Joint Panel Meeting The U.J.N.R. Panel

on Fire Research & Safety, Tokyo, Japan, Oct. 19-22,

1976, Part 1. General Report, pp. 265-317 (Building

Research Institute, Ministry of Construction,

Tokyo, Japan, 1976)

.

New NBSIR 77-1209

752

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 77-1209

CONTROL OF SMOKE MOVEMENT IN

BUILDINGS: A REVIEW

I. A. Benjamin, F. Fung and L. Roth

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

July 1977

Final Report

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

CONTENTS

Page

Abstract 1

1. INTRODUCTION 1

2. EXPERIMENTS TO STUDY SMOKE CONTROL SYSTEMS 2

2.1. National Research Council, Canada

(NRC ) Experiments 2

2.2. Building Research Institute, Japan (BRI) . . . 3

2.3. Commonwealth Experimental Building Station,

Australia 4

2.4. Joint Fire Research Station (FRS)

,

England

(formerly JFRO) 5

2.5. Brooklyn Polytechnic Institute (BPI) 5

2.6. Georgia Tech, Atlanta, Georgia, USA 6

2.7. National Bureau of Standards 6

3. THEORETICAL TECHNIQUES TO STUDY SMOKE MOVEMENT

AND SMOKE CONTROL IN BUILDINGS 8

3.1. NBS Computer Model 8

3.1.1. Assumptions 8

3.1.2. Mass Flows 9

3.1.3. Pressure Relationships 11

3.1.4. Blower Functions 12

3.1.5. Air Properties 13

3.1.6. Solution Procedures 14

3.1.7. Comparison of Computer Models and

Field Studies . 16

3.2. NRC, Canada 16

3.3. Battelle. . 17

3.4. BRI, Japan 17

3.5. FRS, Computer Model 18

3.6. Brooklyn Polytechnic Institute, Computer

Model 19

4. DESIGN METHODS OF SMOKE CONTROL 19

4.1. Passive Methods of Smoke Control 19

4.2. Active Methods of Smoke Control 20

4.2.1. Pressurized Building Method 20

4.2.2. Stairwell Pressurization. ...... 23

4.2.3. National Department of Civil

Protection Method . 26

4.2.4. Commonwealth Experimental Building

Station Smoke Control Method 27

iii
4

•

'

..

.
CONTENTS (cont'd)

Page

5. SUMMARY AND RECOMMENDATIONS . . . , 27

APPENDIX A. BASIC PRINCIPLES OF SMOKE MOVEMENT ... 29

A . 1 . Pressure Differences Due to

Buoyancy Forces 29

A. 2. Pressure Differences Due to

Restriction of Volume Expansion. . 30

A. 3. Pressure Difference Due to Wind

Velocity and Wind Direction. ... 31

A. 4. Pressure Differences Caused by Air

Handling Systems 32

REFERENCES 34

LIST OF TABLES

Table 1. Comparison of Pressurization Procedures in

Various Countries 24

LIST OF FIGURES

Figure 1. General procedure for calculating mass

balance equations in a building including

multiple compartments 15
'
CONTROL OF SMOKE MOVEMENT IN BUILDINGS: A REVIEW

I. A. Benjamin/ F. Fung and L. Roth

Abstract

A state-of-the-art review of efforts in smoke

movement and smoke control is presented. Basic

principles, experimental techniques and results,

computer models, and smoke control methods which

have been employed are presented. The paper

covers all work in the area of smoke movement

and smoke control but emphasizes the work of NBS.

Key words: Basic principles; computer calculations;

computer modeling; experimental methods; smoke

control methods; smoke movement; smoke simulation;

state-of-the-art review.

1. INTRODUCTION

This paper briefly describes the literature in the field

of dynamic smoke movement and control in building fires,

reviews experiments which have been conducted in the area

of dynamic smoke movement and control, reviews computer

models which have been developed to predict smoke movement,

and reviews experience in designing buildings using smoke

control methods. This paper does not intend to be an annotated bibliography, but rather attempts to introduce the reader

to the field of smoke control and acquaint him with the literature .Because of the smoke hazard which can exist during

building fires, methods of controlling the movement of smoke

have been developed. These methods of control have been

divided into two categories: active and passive. Active

methods use the HVAC (Heating, Ventilating and Air Conditioning) system; passive methods use mechanical barriers or vent

shafts to control smoke movement. The active control systems

assume that the fire is "small" enough so that the smoke

generation does not overwhelm the HVAC system; or that the

energy output of the fire is small relative to the energy

output of the HVAC system. This implies that the pressure

differences generated by the HVAC system are much greater

than the pressure differences generated by the fire. Tests

have been made on both active and passive methods by both

actual or simulated fire tests in buildings. Since such

experimentation is very costly and time consuming, mathematical models have been developed to simulate smoke movement

and control under real fire situations; and in a few cases

1
the results of these models have been compared to the results

of experimental tests.

Major contributors to the design of smoke control methods

and to mathematical modeling and experimental testing of these

methods are: the Building Research Institute, Ministry of

Construction, Tokyo, Japan; the National Bureau of Standards,

Washington, D.C., USA; the Fire Research Station, Borehamwood

,

Hertfordshire, England; and the National Research Council of

Canada located in Ottawa. The Commonwealth Experimental

Building Station of Australia; National Department of Civil

Protection in France; Brooklyn Polytechnic Institute Brooklyn,

N.Y., USA; Battelle Memorial Institute, Columbus, Ohio, USA;

and Georgia Institute of Technology, Atlanta, Georgia, USA,

have also made contributions to smoke control methods. This

paper is a summary of the contributions of these selected

sources, with more detailed comments on the work of the

National Bureau of Standards.

2. EXPERIMENTS TO STUDY SMOKE CONTROL SYSTEMS

2.1. National Research Council, Canada (NRC) Experiments

In one set of experiments [1]^ the effectiveness of

stair shaft pressurization systems was tested. The pressurization was accomplished by means of external fans which were

connected to the stair shaft by aluminum ducts. Plastic

tubes 1/4 inch in diameter were strung vertically in the

stair shaft from the top — terminating at several levels

so that the ends of the tube could serve as pressure taps to

measure loss within the shaft. The difference in pressures

between each pressure tap and the top of the stair shaft was

measured with a pressure meter (diaphram type with silicon

piezo-resistive gage) . The tests were conducted with two

outdoor temperatures 2 °C (35 °F) and 10 °C (50 °F)

Experiments similar to those in reference [1] measured

the air leakage of stair shafts and elevator shafts constructed with different types of materials [2]

The results

showed that the leakage values for elevator shaft walls

constructed of masonry units were a great deal higher than

those of cast- in-place concrete. However, for stair shafts

which were constructed of masonry and were plastered the air

leakage rates were similar to those of the elevator shafts

constructed of cast-in-place concrete. They also showed

that the internal resistance to flow within a stair shaft

was considerably more than that of an elevator shaft.

Numbers in brackets refer to the literature references

listed at the end of this paper.

2
Similar experiments measured the air leakage through the

exterior walls of tall buildings [3]

The exterior walls of

the buildings tested allowed relatively high air leakage

rates, similar to laboratory tests on unplastered brick.

As discussed in Appendix A, pressures can build up in a

fire room from the expansion of gas at elevated temperatures,

forcing smoke into adjacent areas in the building. One way

to avoid this pressure build-up is to vent the fire area by

means of a dampered smoke shaft. In the process of venting,

the shaft dampers are exposed to high temperature; and for

the shaft to be effective the dampers must not allow smoke

to leak to other floor areas. A total of six 2-hour fire

tests [4] were performed in the NRC wall furnace to ascertain

the amount of leakage through the dampers of smoke shafts.

Each test involved between three and five dampers. Leakage

tests were performed on the dampers both before and after

the fire tests. The results indicated that rapid and substantial temperature rise is not likely to give increased

leakage, and that curtain dampers, in general, gave less

leakage increase due to fire test than other types.

In another set of experiments [5] pressure measurements

on a 17-story building were taken, using one of the stairwells as a smoke shaft. The smoke shaft behavior of the

stairwell was achieved by opening a vent at the top of the

stairwell. Pressure difference readings between key floors

were obtained both before and during smoke shaft simulation.

Measurements were made with windows in the building closed

and open. The results indicated that the smoke shaft was

effective when the windows were closed, but not effective

when the windows were open.

2.2. Building Research Institute, Japan (BRI)

BRI reported an actual full-scale fire test [6] measuring quantities such as temperature (by thermocouples) , smoke

concentration, 0 2 , C0 2 , and CO in a five-story building

(Welfare Ministry Building) . In this test the burn-room was

located on the second floor. The maximum fire room temperature was 1300 °C (2372 °F) and the average fire room temperature was 650 °C (1202 °F)

The outside temperature was

14.4 °C (57.9 °F) and the wind velocity was 2.5 m/s (.75

ft/s)

The reasons for the test were: (a) to try and correlate

real fire test data with that data generated from the Japanese

computer model (which will be discussed in section 3)

(b) to study the effectiveness of a smoke control method of

3
supplying the stairwells with fresh air to prevent the movement of smoke into the stairwells from the ground floor; and

(c) to analyze the combustion behavior in the Sennishi

Building Fire by studying a test building (Welfare Ministry

Building)

.

The experiment showed that the results generated by the

theoretical model agreed very satisfactorily with the results

generated by the field test on this building, and that the

smoke control method was very effective, provided that there

was a large resistance to airflow between the stairwell and

corridor due to a physical barrier.

Simulated smoke tests were also performed using smoke

candles to study the effectiveness of blowing air into the

stairwells at the ground floor [7]

.

The results showed that

with the burn-room windows open, and the pressurization

system on, the output from the burn-room into the stairwell

was suppressed.

Two tests were performed in the Training Tower, Tokyo

Fire Department, Shibuya, Tokyo. This was a large fireresistive eleven-story building with a basement. The burnroom was located on the fourth floor. Tests were performed

by blowing air into the stairwell with various combination

of opening and/or shutting of doors on the first floor and

windows of the fourth, seventh and eleventh floors. The

results were that smoke movement could not be suppressed

even by forced air if the window to the burn-room was closed.

When the burn-room windows were open, however, this smoke

movement could be suppressed.

A real fire test was performed in ex-U.S. Force's "Ofi

Camp," Kitaku, Tokyo. This was a fire resistive building,

with five stories above the ground, a basement and a penthouse. The burn-room was located on the second floor. Air

was forced into the stair shaft by a fan located on the

first floor. The tests were performed for variable quantities of forced air rates and for a variety of openings of

windows and doors . The average burn-room temperature was

700 °C. The results were that the stairwell pressurization

prevented the movement of smoke into the stairwell.

2.3. Commonwealth Experimental Building Station, Australia

Simulated fire tests were conducted with and without

smoke control [8,9]. The purpose of the experiments was to

test a multi-story office building for smoke movement; and

to determine the performance, under early fire conditions,

of a smoke control system. The office building consists of

fifteen office floors above the ground floor, a lower ground

4
floor, and upper and lower basements opening onto a car

park. Six elevator shafts are continued from the lower

basement to the fifteenth floor and there are three elevators

opening into a separate lobby serving floors from the ground

to the sixth level only. The simulated fire floor was

located on the fifth and tenth floors. The building air

temperature was around 21 °C (70 °F) at the time of test.

Pressure measurements were coupled with the tracing of smoke

movement through the dispersion of warm artificial smoke.

The smoke was generated by entraining heated droplets of

paraffin oil in a stream of carbon dioxide. The pressure

measurements were obtained using differential gages. Smoke

concentration measurements were obtained using optical

density smoke meters with 0.5 meter light paths. These

experiments showed that smoke movement occurred quickly; and

that smoke control procedures should be implemented early.

The experiments also showed that the smoke control procedure,

discussed in section 5, was adequate to prevent smoke

movement.

2.4. Joint Fire Research Station (FRS)

,

(formerly JFRO)

The FRS conducted simulated smoke tests using standard

smoke candles [10] . These tests were conducted at the Pearl

Assurance House. Each floor of the building had open window

areas of 2-1/2 percent of the floor area for ventilation.

The tests measured airflow pressure differentials to determine the effectiveness of a pressurization system for the

stairwells and stairwell lobbies. The system prevented the

smoke from entering the office space even if the stairwell

doors were open. The external weather conditions did not

affect the pressurization system in any way.

2.5. Brooklyn Polytechnic Institute (BPI)

BPI conducted both simulated fire tests, using smoke

candles, and real fire tests in a building [11,12]. The

office building, located at 30 Church Street in downtown

Manhattan, was twenty-two stories. Both smoke and heat were

generated by four fires set at different locations on the

seventh and tenth floors. Maximum fire temperatures recorded

were 928 °C - 984 °C (1500 - 1600 °F) ; and the maximum

pressure differential was 37.5 Pascals 2 (.15 inch Water Gage

1 Pascal = 1 N/m2

5
(W. G. ) ) • The smoke concentration was measured by the attenuation of light. Also during the tests building pressure

differentials were measured by using pitot static tubes.

The tests evaluated a stairwell pressurization system which

will be discussed in detail in section 5. The pressurization

system was found to clear the stairwell of smoke both in

the simulated and real fire situations.

2.6. Georgia Tech, Atlanta, Georgia, USA

A series of smoke tests for simulated and real fires

were conducted in the Henry Grady Hotel, Atlanta, Georgia

[13] to test out a proposed smoke control system for the

City of Atlanta. The Henry Grady Hotel was: a 550-room

fire-resistive building constructed in 1929, a fourteenstory structure of reinforced concrete; stairwells were 98

square feet in cross-sectional area and enclosed a volume of

15,000 cubic feet. The three hotel elevators were contained

in a single shaft of 120 square feet in cross-sectional

area. In the simulated tests, smoke was produced by an army

oil smoke generator which uses a pulse jet engine and fog

oil to produce smoke. The resulting smoke movement was

monitored by optical density smoke meters. The maximum fire

temperature was about 1832 °F (1000 °C) . The test showed

that the proposed smoke control system was adequate, consisting of a 12000 cfm blower, capable of maintaining an

overpressure of 15 in. W.G. in the stairwell.

2.7. National Bureau of Standards

Tests have been performed on five Federal office and

laboratory buildings [14-17] , an apartment building [18]

,

and six VA hospitals [19-22]

.

In all of these buildings, SF 6 was used as a tracer

with the HVAC system in normal and smoke control modes, for

a variety of simulated burn-room locations. Tests were also

performed to determine the results of opening various stairwell doors on the effectiveness of the smoke control mode.

The simulated burn room temperature, where the SF 6 is released,

was in the range of 27 °C (80 °F) to 30 °C (85 °F) . The

burn-room concentration of SF 6 ranged from around 80 to 170

ppb . The range of outside temperatures during the tests was

from -7 °C (20 °F) to around 28 °C (80 °F) . The inside

building temperatures ranged from 22 °C (72 °F) to 26 °C

(79 °F )

.

6
In the Seattle and Chicago Federal Buildings systematic

pressurization is employed for smoke control. In this method

the HVAC system of the fire floor is put on exhaust while the

HVAC system of all other floors is put on supply. In these

two buildings in addition to the SF 6 concentration measurements, a moderate number of pressure measurements and some

meteorological (e.g. temperature and wind speed and direction)

data were obtained.

The Roanoke GSA Building is a 15-story office building,

employing a smoke control mode which will be discussed in

detail in section 5. Extensive pressure measurements and

meteorological data were obtained on this building. It was

found through these tests that the smoke control system was

inadequate. NBS proposed another smoke system, which SF 6 testing and pressure measurements indicated would be effective in controlling smoke.

The Rouse Wates Building is a twelve- story apartment

building located in St. Louis, Missouri. This building

employs a stairwell pressurization smoke control system

with a supply at the top of the stairwell. In addition to

the SF 6 concentration measurements, a limited amount of

pressure and meteorological data were obtained for this

building.

The San Diego VA hospital is a modern six-story structure with a 2.4-meter (8-foot) high interstitial space

between each floor. The building consists of four identical

wings connected to a symmetrical core. The smoke control

for this building was to horizontally pressurize the building so that smoke would not move horizontally from the fire

affected part to a non-fire affected part. In this building

extensive pressure measurements were made and a moderate

amount of meteorological data was taken.

SF 6 tests and a sparse number of pressure and meteorological measurements were performed on two buildings at the

NASA Goddard Space Flight Center, buildings 22 and 23,

which are four-story office buildings. The tests showed

that the existing smoke control mode of exhausting the burn

floor only, while all other floors were normal, was not

adequate. It was suggested (but not tested) that pressurized

stairwells be installed as a smoke control method.

sf

6 tests were also performed on the San Antonio VA

hospital to determine smoke movement. This building has a total of seven floors above grade. This building did not

have a smoke control system. The results of the tests

showed that the interstitial space served as a smoke absorbing void in reducing smoke infiltration. It was suggested

7
that a smoke removal system be implemented in the interstitial spaces of this building.

SF 6 tests and pressure measurements were also performed

on the Hines VA hospital. This building has 15 floors and a penthouse above grade level. Also the first and second

floors were connected to another building, at grade level,

by a corridor through which air moved due to stack effect.

This building also has no smoke control system. Potentially

hazardous areas of high smoke concentration were established

for various fire locations. A smoke control system, has

been proposed for this building and follow-up tests are

planned when this system is put into operation.

3. THEORETICAL TECHNIQUES TO STUDY SMOKE MOVEMENT

AND SMOKE CONTROL IN BUILDINGS

3.1. NBS Computer Model

This model has been developed by Integrated Systems,

Inc. under contract to NBS. A detailed description is given

of this model since it attempts to integrate many of the

features of the other existing models.

3.1.1. Assumptions

The base for the NBS model is described here. Because

of the complexity of the smoke simulation model many simplifying assumptions are necessary and used in the existing

models to keep the problem tractable. The model employs the

basic principles of smoke movement which are discussed in

Appendix A.

1. Smoke is assumed to move in the same manner as air.

Thus smoke movement between compartments depends on the

pressure gradients existing between these compartments.

2. It is assumed that the fire is small. In the case

of smoke control, only low energy fires, or the incipient

stage of a developing fire is considered. For this case the

output energy of the smoke control system (see page 1) is

large relative to the fire energy.

3. The pressure forces are in steady-state.

4. Diffusion is considered instantaneous within a given compartment, so that the concentration at any given

time within the compartment is uniform. The effect of this

assumption is to impose a conservative approach to the

build-up of smoke in a given space.

8
5. The temperatures for the internal parts of the

building including the fire areas are known.

In the mathematical model three types of equations are

needed: (1) equations describing the movement of the fluid

(mass balance and momentum); (2) equations of state, which

is the relationship between pressure, temperature, and

density of the fluids; and (3) the species conservation

equation, which describes the smoke concentration build-up.

3.1.2. Mass Flows

The mass flow rate equilibrium equation for the simulation of the steady-state air movement in a building space

is

:

+ F

2j + F. . +

13 + F

n: = 0 ( 1 )

where F. . is the mass flow rate of air between the

il

i-th and j-th building spaces.

This equation is solved for each corridor and compartment

on each floor, for all shaft openings, for each supply duct

network, for each return air duct network, and for each Air

Handling Unit (AHU) . The system of equations that must be

solved in each case is completely dependent on the building

system modeled by the program user. The mass flow rate for

different openings sometimes referred to as the orifice

equation (and which is a combination of mass flow and momentum equation) is as follows.

where

F = k X

v 1 2x

A P

X

(2)

P K is determined as a function of the type of

opening, the effective area, and the appropriate flow coefficient for the above types

of openings. A moderate opening is defined

as having an area the order of 0.01 m2 (.1 ft 2

) to .1 m2 (1 ft 2 ). Openings with

areas larger than this are classified as large

openings, while those having smaller areas

are classified as small openings.

x is 1/2 for the large and moderate openings

and 1 for the very small or crack-type

opening.

F is the mass flow rate (kg/s)

9
p is the density of air on the inlet side

(kg/m 3

)

AP is the pressure difference (k.g/m 2

)

y is the viscosity of air on the inlet side

of the opening.

External wind leakage can be a significant factor in

the effectiveness of the smoke control system and, under

certain conditions, can defeat the use of an HVAC system in

controlling pressures within a building. Consequently,

program capability was provided to define varying conditions

operating on the external walls of the simulated building.

Ten external wind states, depending on the wind direction

were included in the design of the program. Each of these

states was then defined by a wind speed normal to the wall,

varying with height and at a given temperature. The velocity includes the pressure coefficient, which appears in

other models, as will presently be discussed. Temperature

is held constant for each wind state. The velocity is given

by

V = f(h

i ,T) (3)

where V is

T is

f (h. , T) is

i

h. is

l

Excluding an

directly with the

of the simulated building is determined as a function of the

pressure difference and the degree of leakage in the walls.

Consequently, the pressure due to the wind at any given

floor level and on any given external wall must be determined,

The dynamic pressure due to the wind was defined as

P

where

= 1/2 p V2

is the dynamic wind pressure (N/m 2

) is the density of the outside air at the

given height and temperature (kg/m 3

) 10

( 4 )

P
V is the wind speed at the given height on

the given external wall (meters per second)

.

3.1.3. Pressure Relationships

Critical to a meaningful simulation is the representation of the airflow behavior within an open shaft, such as a stairwell, elevator shaft, or plumbing chase. Two basic

situations are usually encountered with such shafts: (a) a

non-pressurized shaft which is coupled for air movement

purposes by leakage passages, and (b) a pressurized shaft

with specific and designed flow openings as well as leakage

openings

.

In a non-pressurized shaft the pressure is selected at

a most probable location of the largest flow in the shaft.

In a pressurized shaft, i.e., where an inlet blower

exists and/or a pressurized condition exists, another

relationship was introduced to include the effects of the

blower or fan pressurization. An equation (duct equation)

was introduced to provide a means of determining the vertical pressure distribution within a pressurized shaft, i.e..

AP 10

AP 10

.00020393 T F

2

I A h| f

o

(A)

(5)

is the pressure loss between the fan inlet to

the shaft and the major outlet (N/rn )

T = is the average temperature between the shaft's

inlet and outlet (K)

Ah = is the vertical distance between the shaft's

inlet and outlet (m) . (In the case of the

stairwell, a correction factor is included.)

A = is the average area in the shaft between the

inlet and the outlet (m 2

)

P

I0 = is the average pressure in the shaft between the

major inlet and the major outlet (N/m2

)

11
f is the friction factor (which is a

Reynolds Number)

function of

- F

o

is the mass flow rate at the shaft outlet (kg/min)

The duct loss equation is solved iteratively as an implicit

function where

F

o “ * ( V P

ext>

(6a)

Ho

leu II -€r •a o

>a H

(6b)

p

o

is the pressure at the outlet

P

ext is the pressure on the external side of the

outlet

P

I

is the pressure in the shaft at the inlet

.

The duct loss was assumed to occur between the major

inlet point and the major outlet point, where either one

could be physically above or below the other. The distance

over which function loss occurs was assumed to be the

distance between these two locations, except in the case of

a stairway. In the case of a stairwell, a lengthened

channel was assumed due to the energy losses of a stairwell,

and the vertical distance between the defined inlet and

outlet was multiplied by a correction factor.

The loss in pressure was included in the continuity

condition. A linear relationship was used between the inlet

and the outlet to provide the vertical distribution of the

pressure loss. If a shaft extends beyond an inlet or outlet

a stagnant condition is assumed, with the pressure determined from the inlet or outlet pressures, respectively.

3.1.4. Blower Functions

Initially, an attempt was made to represent a fan or

blower as a function of typical fan or blower characteristics

and the air state at either the inlet or the outlet. However, the conditions were too complex. As a result, two

methods of specifying a fan or blower, both of a simple

form, were utilized.

12
The first method allows a user to specify a blower

rotational speed (RPM) , horsepower, and an outlet area.

From tabular data representing a family of blowers, throughput is determined, i.e., static discharge pressure and

volume flow rate at standard conditions.

The second method allows a user to specify the static

discharge pressure and the volume flow rate under standard

conditions

.

In either case, the volume flow rate is converted to

mass flow rate; i.e..

QB Vs (7)

is the mass flow rate output of the blower/fan

B (kg/min)

F is the specified volume flow rate output of

the blower/fan (m 3 /min)

p is the density of air under standard conditions

(kg/m 3

) The mass flow rate from a specified blower enters the

equilibrium equations coupled at the blower, except in the

case of blowers, effectively as a boundary condition, i.e.,

the mass flow rate for that component is fixed and not

allowed to vary as a function of the iterative processes.

The given static discharge pressure is of particular

importance in the case of pressurized shafts and enters the

solution via the duct loss equation in the continuity relationship. In other cases, where the flow only enters the

equilibrium equation, the given static pressure is not

directly used.

3.1.5. Air Properties

Air density was calculated at each point in the program

as a function of the temperature and pressure of the building space involved in the calculation; i.e., at a constant

height

,

.3012 P

T

P is density (kg/m 3

)

P is the pressure (N/m 2

) T is the temperature (K)

13
The air within an open shaft was treated as a continuous medium and the pressures were determined as a function

of the controlling flow and the height. The density became

appropriately variable as a function of height. The viscosity of air is a function of temperature and linear

segmented curve fit was made over the range of anticipated

temperatures

.

The method of solution chosen for all corridors and

compartments on all floors, all shafts, each duct supply and

return network, and for each air handling unit (AHU) was a nested iterative solution. The matrix which is generated is

nonlinear. Initial values for the pressures for each space

are chosen based on the nominal interior state and external

ambient condition. When the pressures are chosen, and the

temperatures are specified, the densities are known. Thus,

the flows can be determined through the orifice equation.

These results are substituted into the equilibrium equation.

If the right-hand side of the equation is not zero the

pressure is incremented and the above process is repeated.

When the zero value is reached, the orifice state and

continuity equations are solved for the next space. This

process goes on until all the pressures in all spaces have

been solved. Figure 1 is a diagram of this process.

The second step of solving for the smoke concentrations

if the mass flow rates are known can be obtained by the

species conservation equation as follows:

3.1.6. Solution Procedures

dC .1

N

dt

( 8 )

is air density

V.

i

is the compartmental volume

t is the time.

14
Figure 1. General procedure for calculating mass

balance equations in a building including multiple

compartments

.

15
At the present time the smoke concentration program is

limited to the movement of smoke between a corridor and a shaft and between corridors by a floor to floor leakage

term. This program is being modified to remove this limitation. Presently there is no means of predicting lateral

movement or to account for all of the various spaces and

paths available from the air movement program, or that

exist in a real building. This places a significant burden

on the user to preselect the shafts which are to be used by

the smoke concentration program. This implies that the user

must guess, in advance of the air movement simulation, which

shafts will be significant. If the user selects the wrong

set, he will get erroneous and misleading results.

Although all characteristics of all building systems

cannot be specifically represented by the capability of the

computer program, the functional representation of almost

all characteristics can be modeled by simulation of the

available characteristics. Reviews of the NBS smoke movement computer model program are reported in [23-27]

.

3.1.7. Comparison of Computer Models and Field Studies

To determine if the simulation realistically represents

the pressure differentials and smoke concentrations measured

by SFg tests, five of the buildings discussed in section 3

were simulated by the movement and smoke concentration

programs

.

The San Diego VA hospital [28] , Hines VA hospital [29] , NASA Goddard Buildings [30] , and the Seattle Federal Building

[31]

,

were parametrically modeled and the model was calibrated against field acquired pressure and/or trace gas data

collected with the HVAC system in various modes. In most

cases the computer model agreed with the experimental tests.

3.2. NRC , Canada

The computer model used at NRC is the forerunner of the

one now being used at NBS [32]

.

The assumptions in this

model are basically the same as for the NBS model. The

differences between the two methods are: (a) the NBS model

is more general in its capability to handle different

building configurations, (b) the NBS model includes friction

in shafts (c) the NBS model solves for the absolute pressure

levels whereas the NRC model yields pressure differences,

and (d) the solution technique for the NRC model is to solve

iteratively a linearized matrix of the equilibrium equations

whereas the NBS method solves a nonlinear equation system

iteratively

.

16
3.3. Battelle

Battelle Memorial Institute [33] also used a computer

model similar to the NRC computer model. However, the

Battelle model was designed to model only the stack effect

and is of a much more limited nature than the NRC model.

3.4. BRI , Japan

BRI considered both steady and unsteady models for an

air movement program. In the steady situation, they considered two types of programs, a simplified steady-state and

a precise steady-state model. The simplified steady-state

is a method for solving the mass balance equations only for

sources where the major flows are found.

In the precise steady-state model there are two ways of

modeling thermal states: methods A and B. Method A specifies

the temperatures throughout the building. Method B specifies

all the building temperatures except the temperatures in the

corridor adjacent to the burn-room. In this corridor, a twolayered flow of smoke above air is considered. The degree

of stratification depends on the Reynolds number and Richardson number [34,35]. This situation partially removes the

restriction that the air and smoke in all spaces are completely mixed.

If method A is used, the precise steady-state program

is comparable to that at NBS , except for minor variations

such as the wind pressure expression and the type of orifice

equation which is used in the corridor adjacent to the burnroom.

If method B is used, a two-layered flow in which smoke

above air is considered, the temperature of the smoke layer

is found to decay exponentially with horizontal position

(but not time) from the burn-room. These methods intend to

solve the problem of the steady-state, or quasi steady, movement of smoke and air in a building as a whole, by computing

the quantity of smoke and air flowing through each opening

or flow path. The localized flows in specific rooms are

neglected in this treatment.

In the unsteady situation the problem of changing

building space temperatures and external building temperatures is considered. The burning rate of the fire compartment varies according to the following relationships

17
R 350 x t (Kcal/min) ; 0 < t < 10 (min) (9a)

R 3500 (Kcal/min)

;

t > 10 (min) (9b)

where t is the time.

An energy equation is used to describe the temperature

profile

.

A discussion of the above Japanese models can be found

in [36-38]

.

The Evers and Waterhouse computation method for smoke

movement in high rise buildings [39] is very similar to the

precise steady-state model of the BRI , using method B [36].

The differences between the two models are as follows:

(a) the FRS solve their equations for pressure differences

rather than for absolute pressures; (b) the method of solution

used by the FRS is the same as that used by NRC ; and (c) the

FRS allow their program to operate in either of two modes;

deterministic or stochastic. In the deterministic mode, the

input variables are specified. This mode calculates smoke

movement as a result of a particular type of fire under

specified environmental conditions. In the stochastic mode,

which is used to calculate building risk levels, the stochastic

variables are sampled at random from specified statistical

distributions using a Monte Carlo technique for each pass.

The following are the stochastic parameters of the model:

1. Location of the fire

2. Temperature of the fire

3. Smoke concentration in the fire compartment

4. Ambient air temperature inside the building

5. Ambient air temperature outside the building

6 . Wind speed

7. Wind direction

8. Area of each door opening

9. Area of each window opening

10. Time at which the door of the fire compartment

burns down

11. Time at which the window of the fire compartment

breaks

3.5. FRS , Computer Model

18
The following variables are also considered:

1. Size of cracks around doors

2. Size of cracks around windows

3. Reliability of the ventilation system.

3.6. Brooklyn Polytechnic Institute, Computer Model

The BPI model [40] idealizes the stair shaft as a duct

in which the flow is quasi one dimensional. A momentum

equation is written expressing the pressure change with

height as: a function of the area change of the shaft, the

temperature change in the shaft, the mass flow change in the

shaft (e.g., due to leakage), the frictional drag in the

shaft, and the hydrostatic effect. The exact expression of

these functional relationships involves constants which are

determined by model scale experiments.

4.

DESIGN METHODS OF SMOKE CONTROL

Although the passive methods are briefly mentioned in

4.1, the primary purpose of this paper is to discuss the

active methods. There are many methods of smoke control.

These methods include the passive methods of top or bottom

venting, and use of smoke shafts for evacuation of smoke,

and the active methods which use the HVAC system for various

types of active smoke control.

4.1. Passive Methods of Smoke Control

The passive smoke control methods of top or bottom

venting of a shaft, and use of non-pressurized smoke shafts

are the older smoke control methods. These methods are

particularly sensitive to environmental changes. They are

not subject to adjustment and control as are the active

methods. Top venting raises the level of the neutral plane

of the shaft. The optimum top vent area is the minimum area

that raises the position of the neutral plane to the top of

the shaft, so that flow from every building floor is into

the shaft. Top venting can assist in the evacuation of

smoke which has leaked into a shaft from the fire floor and

can keep it from going into other floors. Since top venting

of a shaft causes the shaft to become filled with smoke it

is highly desirable that a specially dedicated shaft be

provided for venting. Thus, stair shafts and elevator

shafts should not be top vented.

19
Bottom venting of a shaft lowers the level of the

neutral plane of the shaft. The optimum bottom vent size is

the minimum area which lowers the neutral plane of the vent

to the first floor. Bottom venting prevents smoke from

entering the shaft. Thus, bottom vented shafts can be used

for evacuation in the event of a fire. The theoretical concepts for top and bottom venting as methods of smoke control

are set forth in NRC publications [41-43] and are based on

their theoretical computer model, and on experimentation.

The smoke shaft is a top vented shaft dedicated to

smoke removal, which has openings to all the building floors.

These openings are controlled by dampers. When the damper

on the fire floor is opened smoke moves out of the fire

floor into the shaft because of top venting [5]

.

Sometimes a smoke proof tower is used to prevent stairwell contamination [5,44,45]. This smoke tower consists of

a vestibule between each story and the stairwell, with an

opening either directly to the outside or to a smoke shaft

in one of the vestibule walls. This design can be improved

if the vestibule is pressurized. Also the efficiency of

smoke removal of a smokeproof tower can be increased by

heating the air in the tower with a heater [45]

.

Inflatable smoke shutters are used to contain smoke

movement [46-48]

.

These shutters are composed of fire

resistant material and are normally folded in nonfire conditions. In the event of a fire, these shutters are released

and can block the movement of smoke through a passageway.

4.2. Active Methods of Smoke Control

Smoke control by the HVAC system is an active means of

smoke control. Smoke control by the HVAC system may be by

building pressurization, including systematic horizontal and

vertical pressurization, by pressurization of corridors, or

by pressurization of stair shafts or smoke shafts.

4.2.1. Pressurized Building Method

The building HVAC system is operated to supply enough

air to pressurize all floors above the outside atmospheric

pressure [49-51] . Because of leakage into the stairwell and

elevator shafts, these shafts are also pressurized above the

external building pressure. In the winter-time, because of

the stack effect the inside to outside pressure difference

of the building increases from bottom to top of the building.

20
According to estimates by Tamura, McGuire, and Wilson [50] c 90 m 3 /min (3000 cfm) of air per building story were needed

when the outside temperature was 24 °C (75 °F) and the

building temperature was 21 °C (70 °F) . The authors also

suggest an added flow of 9.0 m 3 /min per typical stairwell

door into the stairwell to make up for leakage. These

studies were done on a 20-story model building with 120 by

120 ft floor plan. These NRC estimates are now incorporated

into the Canadian National Building Code.

In the absency of an adverse wind or stack effect smoke

control can be improved if the fire floor can be vented to

the outside, by means of an opening in the building (e.g.

broken window) or to a smoke shaft. This creates a lower

pressure in the fire floor relative to the other floors and

to the shafts of the building and smoke is contained on the

fire floor.

NBS has been studying various modes of building pressurization as a method of smoke control. One method of

systematic pressurization [14,15,52] consists of dividing

the building vertically into horizontal zones to be served

by separate air handling systems with each zone containing

several floors. In the event of a fire, the HVAC system is

switched to a smoke control mode: the fire zone is exhausted

and the nonfire zones are supplied with air. This situation

creates a positive pressure in the fire-free zones in reference to the fire zone; and prevents smoke movement from the

fire zone into the fire-free zones. The optimum number of

floors in each zone is found when there is enough pressure

difference created by the HVAC system across the stairwell

doors to counteract the flow of smoke from the fire floor,

but at the same time the pressure difference is not large

enough to prevent opening the stairwell doors.

A practical design approach in systematic pressurization is the variable zoning approach [52]

.

The amount of

flow to each zone is proportional to the number of floors in

the zone. In the variable zoning approach the supply to

each zone can be varied so that the zones requiring the

largest amount of flow include the most floors. Thus, in a

leaky building, in which the stack effect is very important,

and the neutral plane is at midheight the zones incorporating the most floors will be the top and bottom zones. The

systematic pressurization technique was studied in the field

on both the Chicago Federal Building and Seattle Federal

Building.

21
A zoned systematic method of smoke control, with no

horizontal separation, was able to prevent smoke from infiltrating through either stairwells or elevator shafts under

both summer and winter conditions in the Seattle Federal

Building [14,15]. In addition to confining smoke to the

floor of origin, the system was able to effectively reduce

the smoke concentration to below 1% of the burn-room concentration, except in the immediate simulated fire area; even

with as much as 15 minutes of delay in switching from the

normal mode to the smoke control mode

.

In an airtight building such as the Chicago Federal

Building [14] , in which the pressure due to the stack effect

was almost negligible, since the outside temperature was

6 °C to 10 °C (42 °F to 50 °F) , the force across the stairwell door was about 25 Pa (0.1 in. W.G.), with a maximum

recorded pressure of 50 Pa (0.2 in. W.G.). Such pressure

calls for an additional force of 40 Newtons (9 lbs) to open

the stairwell door. This is the additional force required

over and above that needed to counteract the door closer.

Another example of systematic pressurization was studied

in a 13-story GSA building in Roanoke, Virginia. The tower

portion consists of floors 2-13. The planned smoke control

mode is as follows: each floor is divided by HVAC zones (no

physical barrier exists) into an east side and a west side.

If a fire occurs on a floor on the east side, this side is

exhausted, and the west side of the fire floor is put on

supply; also the east side of the floors above and below are

put on supply. All return fans on the east side of the

building are put on half speed because of concern over the

fiberglass ductwork of the HVAC system collapsing. The HVAC

system operates normally in all other parts of the building.

If a fire occurs on the west side, the smoke control procedure is the reverse of the one just discussed.

This type of smoke control mode was found inadequate

because pressure gradients could not be established on the

fire floor to prevent smoke movement, since no physical

barrier exists between east side and west side. Also,

pressurizing only one side of one floor both above and below

did not prevent smoke infiltration into the shafts. For

example, with a simulated fire in the east wing of the 4th

floor, the 4th floor corridor had 6.3 Pa (.025 in. VI. G.)

positive pressure differential in the east stairwell and the

west wing had 5.0 Pa (0.02 in. VI. G.) pressure differential

in the west stairwell. The investigation indicated that the

best method of smoke control for this building would be to

pressurize all floors above and below the fire floor and to

exhaust the entire fire floor.

22
In reference [20] horizontal pressurization as applied

to the San Diego VA Hospital is discussed. For this situation the building being studied was divided into four wings

enclosing a central core. In the situation of a fire in one

of the wings, the affected wing is exhausted and the nonaffected wings are pressurized. Thus, a positive pressure

gradient is maintained from the nonaffected wings to the

affected wing. Pressure differences generated in this

situation are on the order of 7.5 Pa (0.03 in. W.G.).

4.2.2. Stairwell Pressurization

Some systems have been designed to pressurize stairwells

only, and not the total building. This procedure will keep

the stairwells smoke free but not the building itself.

Table 1 taken from [53] gives a comparison of the requirements for stairwell pressurization in various countries. As

can be seen from the table, the requirements vary considerably between countries. Some countries have considered

stairwell pressurization as an adequate smoke control solution and many different methods of stairwell pressurization

have been developed.

One experimental design, studied by NBS and tested in a

12-story building in St. Louis, Mo., had a stairwell pressurized by providing a mechanical air supply (fan) at the top

of the shaft with 280 m 3 /min (10,000 cfm) plus 2.8 m/min

(100 cfm) for each door [18] . The stair shaft had a vent at

street level. The stairwell opening is directly to the

outside. The area of the vent opening is 1.84 m2

, (20 sq

ft 2 ).

With the pressurization system on for a fire in the

second floor, under moderate temperatures (outside around

16 °C (60 °F ) and inside at 24 °C (75 °F) ) the SF 6 concentration in the stairwell at 15 minutes after the start of the test

was below 0.1% of the SF 6 concentration in the burn-room.

When the pressurization was off the measured concentration

at 15 minutes in the stairwell ranged from 4 to 70% of the

burn-room concentration. The maximum force needed to open

the stairwell doors with the pressurization was around

19.6 Newtons (43 lbs). This occurred on the eleventh floor,

near the blower outlet. This large force is a disadvantage

for the single outlet pressurization system.

The BRI method of stairwell pressurization is to

pressurize with an air supply at the bottom of the stairwell

[6]. A self-closing door is used between the fire floor and

the shaft. For the five-story Welfare Ministry Building,

supplying 1000 m 3 /min (33300 cfm) into the stairwell, smoke

in the stairwell was removed in 1-1/2 minutes.

23
Table 1. Comparison of Pressurization Procedures in Various Countries

Country and Code Mechanical Ventilation Requirements

AUSTRALIA

N.S.W. Code

Pressurize Stairways, Ramp, or Passageway to 50 Pascals

(0.2 inch Water Gage); Air Velocity of 1 m/s (200

ft/min) through open door, design for 10% open.

CANADA

National Building

Code of Canada

Pressurize whole building or Stairways and Elevator

shafts. No figures for excess pressure levels given

but air supplies needed defined in detail.

USA

San Diego and

Los Angeles

Stair shaft pressurized to 12.5 Pa (0.05 in. W.G.)

with 1.2 m

3 /s (2500 cfm) extraction at top of stair

shaft. Lobbies at a reduced pressure of 25 Pa (0.10 in.

W.G.) below minimum stair pressure with an exhaust of

2500 cfm from each lobby. Air supply to lobbies not

specified

.

New York City

Building Code

Stair shaft pressurized to 12.5 Pa (0.05 in. W.G.) at

the fire floor with a minimum of 5 Pa (0.02 in. W.G.)

at all other floors. (Max. door opening force 11.4 kg

(25 lbs) at door knob.

Uniform Building

Code of USA

Stair shaft pressurized to 12.5 Pa (0.05 in. W.G.) with

a 1.2 m 3 /s (2500 cfm) extraction at top of stair shaft.

Lobbies have extraction and air supply to give 1 air

change per minute with extract at least 150% of air

supply. Lobbies shall be at least 25 Pa (0.10 in. W.G.)

pressure below stair shaft.

BELGIUM

N.B.N. 713.011

Stair shaft pressurized to 50 Pa (0.20 in. W.G.); other

conditions not specified yet, although an unspecified

minimum air velocity through an open door is mentioned.

FRANCE

Directive of

1967

Stairwell brought up to a positive pressure, large

extraction from lobbies, and pressure in lobbies is

lower than in the stairwell but higher than in the

neighboring corridor or accommodation spaces.

UNITED KINGDOM

Code now in draft

Stairwell and lobbies pressurized to value of up to

50 Pa (0.20 in. W.G.) depending on building height.

Pressure in lobby equal to or slightly less than that

in stairwell. No extraction from either stair or lobby. Positive measures to ensure adequate air

leakage from accommodation spaces at building perimeter.

24
Methods of stairwell pressurization are also suggested

by NRC [1,40,54,55]. Experimental tests and theoretical

studies were conducted on buildings with the air supply at

both the top and bottom of the shaft. It was found that

with the stairwell doors to both the fire floor and ground

floor open, a supply rate based on a rate of uniform pressurization of 25 Pa (0.1 in. W.G.) at all levels maintained the

stairwells smoke free. When more stairwell doors were open,

there was increased possibility of stairwell contamination

with smoke

.

With air injection into the bottom, there was a substantial loss of supply air through the open exit door at

the ground floor. When air was injected at the top, there

was a high leakage rate into the upper floors; and in addition an increased pressure gradient across the upper floor

stairwell doors. Both Tamura [1] and Fung [18] concluded

that the best stairwell pressurization method would be a

more uniform pressurization method in which air supply is

injected at several levels. This uniform pressurization

scheme was studied by Shaw and Tamura [56]. Air injection

occurred at every fifth floor starting from the top, since

multiple injection is more effective than single injection

for providing an uniform air supply for dilution in the

event smoke penetrates the shaft. A further step, used by

Shaw and Tamura for uniform pressurization, was to provide a

top vent.

BPI experimental work [11] pressurized stairwells by

injecting air at the bottom of the stairwell by a fan located in the bottom stairwell doorway and exhausting the air

through a fan in the roof vent, or by injecting air into the

roof vent through a fan and exhausting the air out a bottom

stairwell door. They also studied stairwell pressurization

by injecting air at a maximum velocity of 900 m/min (3000

ft/min) at the top and bottom of a stair shaft. Although

they did not obtain uniform stairwell pressure profiles, the

report suggests that a routine pressure of 5 Pa (0.02 in.

W.G.) with respect to the floor space should be maintained

throughout the stair shaft, except at the fire floor where

a positive pressure of 12.5 Pa (0.05 in. W.G.) should be

maintained with respect to the floor space. To accomplish

this profile, they suggest the possibility of injecting the

air at multiple levels in the shaft and recommended that a

maximum velocity of 600 m/min (2000 ft/min) flow through a

single open stairwell door and a maximum door opening force

of 11 . 4 kg (25 lbs)

.

25
Erdelyi [57] has used a system of uniform injection and

uniform exhaust of a stairwell. The injection rates and

exhaust rates are respectively suggested at 11.2 m 3 /min (400

cfm) and 7.7 m

3 /min (275 cfm) . The location of the intake

fans are placed at random points on the windward side of the

building so as to minimize smoke contamination by the intake

system. The exhaust intakes are located as close as possible

to the stairwell entrance door so as to remove as early as

possible any contamination that would enter the stairwell

upon opening this door.

Butcher [10,53] in Great Britain has proposed that in

addition to uniform pressurization across the stairwell,

which in England is 25 to 50 Pa [0.1 to 0.2 in. W.G.] , the

stairwells should also be protected by pressurized lobbies

or vestibules. The pressure in the lobbies should be equal

to or slightly less than the stairwell. This pressure

should, however, be a minimum of 25 Pa (0.1 in. VI. G.) above

that in the accomodation. If the stairwell pressure is too

large (i.e., 100 Pa (0.4 in. W.G.)) then difficulties might

arise in opening stairwell doors. With this pressurization

system air flows out of the stairwell, through the lobbies,

along the corridor to the fire area, and out of the building

at the external wall.

The FRC uniform stairwell pressurization technique

requires supply duct openings at every floor level of the

stairwell [10,53]. The air for the lobby and stairwell

pressurization should be drawn from a point where there is

no smoke, e.g. near the ground. Also independent pressurization systems for the stairwell and lobby are needed.

4.2.3. National Department of Civil Protection Method

The French use a dilution system, in which air is

introduced into and smoke is extracted from corridor lobbies

or staircases [58,59] to maintain a crawling height safe

level in the corridors. Also smoke and air are extracted

from the fire compartment. The system does not establish a

pressure gradient to control smoke movement. The only

physical barrier between the lobby and horizontal corridor

is a smoke door. The system requires a balance between the

supply and exhaust rate; and there is a danger that if the

extraction rate is greater than the supply rate a negative

pressure gradient from stair shaft to floor space would be

established, causing smoke to move into the stair shaft.

26
4.2.4. Commonwealth Experimental Building Station

Smoke Control Method

The Australian code of smoke control is as follows [8]

:

in the event of a fire in which smoke does not penetrate

into the supply or return air ducts of the HVAC system,

pressurization of fire escape exits and fire isolated shafts

is started; if the smoke penetrates into the return air

system, the fire isolated shafts are pressurized, the return

air system is exhausted to the outside with only clean

outside air delivered as supply air. If smoke penetrates

into the supply air system, the supply fan and pressurizing

fan are shut down and the outside air fan dampers are closed.

When clean air is again available, supply and stairwell

pressurization are reversed. One feature which is not

required, but is recommended in the code is automatic closure

of the damper controlling the supply air to the fire floor,

continued exhaust from the fire floor and supply and exhaust

of all other floors.

5. SUMMARY AND RECOMMENDATIONS

5.1. A considerable number of buildings have been field

tested to study smoke movement. From a review of the literature it appears that the simplest and most meaningful experimental test method for measuring smoke movement is the SF 6 test, used in conjunction with pressure measurements. These

tests can be performed in an occupied building during working

hours and are completely unnoticed by the people who work in

the building.

5.2. The steady-state computer methods of the BRI and

FRC model a steady-state pressure profile, with a mathematically obtained, temperature profile, in the corridor

adjacent to the burn-room. The BRI unsteady air movement

model is designed to model unsteady pressure and temperature

profiles in the corridor adjacent to the burn-room.

The NBS method can model a larger number of building

variables than the other methods. However, the smoke concentration program cannot simulate lateral movement or

account for all various spaces and paths that exist in a building. This places a significant burden upon a user

since he must preselect the vertical shafts which are to be

used by the smoke concentration program.

A defect of all models is that instantaneous mixing is

assumed in a compartment, except in the corridor adjacent to

the burn-room in the British method and steady-state method

B of the Japanese. In a large fire this mixing has a large

27
effect on the building temperature and pressure profiles

and, therefore, on smoke movement. Further, no provision is

made for the transport due to turbulence from the point of

entrance of the smoke into a given space to the point of

passing into another space. The NBS model is now being

further developed to handle some of these limitations. The

assumption of instantaneous mixing of smoke and air is a

worst possible case and requires the HVAC system to work

harder than is necessary to remove the smoke. This necessitates more fuel consumption and higher operating cost of the

HVAC system in the smoke control mode.

5.3. A considerable number of field tests have been conducted

by NBS to study the qualitative aspects of smoke control; to

provide input into the NBS model and to calibrate the model

for use on existing buildings. With the model calibrated

for an existing building parametric studies of smoke movement can be done on the computer.

5.4. If smoke is to be controlled in high-rise buildings, to

protect the building occupants without complete evacuation

of the building, then some type of building pressurization

approach should be used. The variable zoned method provides

a comprehensive approach- to a pressurized building smoke

control systems.

5.5. If smoke is to be controlled in high-rise buildings so

that evacuation of the building occupants takes place by

means of the stairwells, then a method of uniform stairwell

pressurization should be used. The stairwell pressure should

be 25 to 50 Pa (0.1 to 0.2 in. W.G.) above the pressure in

the floor space. Also, the stairwell should not be vented,

since compensation for the leakage requires a pressure buildup in certain levels.

5.6 For a building which is divided by a physical barrier

into horizontal sections a method of horizontal pressurization

may be employed to control smoke movement. By using this

method both evacuation of the nonfire wings of the building

and property loss are reduced.

5.7 There is considerable diversity today in the approaches

used by various countries to achieve smoke control. The

techniques and the technology are new; and much expense will

be required before optimum solutions can be postulated.

28
APPENDIX A. BASIC PRINCIPLES OF SMOKE MOVEMENT

One of the basic assumptions in the analysis of smoke

movement is that smoke moves with the air along pressure

gradients. As indicated by Fung [18], pressure forces can

originate by, (a) restriction of volume expansion, (b) by

buoyancy forces, including the stack effect, (c) by the

effect of wind velocity, and (d) by the pressure differences

imposed by the air handling systems.

A . 1 . Pressure Differences Due to Buoyancy Forces

In references [18] and [20] are detailed discussions of

(a), (b) , and (c)

,

as cited above, including derivation of

formulas from basic principles and comparison of orders of

magnitude. The buoyancy force between air at ambient temperature and air containing smoke at higher than ambient

temperatures can be expressed as

where

APb

= 3600 (±- - H (Al)

APg is the pressure difference due to the

buoyancy force (Pascals)

H is the heated air column height (meters)

T is the temperature of the smoke column

(K) at height (H)

T

q

is the ambient air temperature (K)

For a fully developed fire, with a gas temperature

reaching about 870 °C (1600 °F) in a room of about 3.1 m

(10 ft)

,

the pressure difference in the room due to the buoyancy force i 25 Pascals (0.1 in. W.G.).

Another type of buoyancy force involved in smoke movement in buildings is caused by stack effect. This force is

generated by differences in densities due to the difference

in temperature between air inside and outside of a building.

The pressure difference due to the stack effect can be

written as

AP = 3600 / -) h

V T T/ ' o

(A2)

29
where AP is the pressure difference due to the

stack effect (Pascals)

h is the height (meters) above or below

the neutral plane of the building (the

position where AP = 0)

T is the inside building temperature

T

q

is the outside building temperature

The form of equation (A2) is identical to that of (Al)

:

the difference is in the meaning of the height term. Equation

(A2) indicates that for a 31-meter (100-foot) tall building

with the neutral plane at mid-height and a 39.2 °C (70 °F)

temperature differential, a stack effect or pressure difference of 25 Pascals (0.1 in. W.G.) would exist.

In the winter time the building temperature is higher

than the outside temperature. Below the neutral plane at

this time of the year the pressure outside the building is

higher than inside, and the flow in the lower floors moves

from outside the building to inside. Above the neutral

plane of the building the reverse condition occurs. The

position of the neutral plane is determined by the condition

that the mass flow into the building below the neutral plane

is equal to the mass flow out of the building above the

neutral plane. In the summertime, the flow directions are

the reverse of the winter time.

In addition to the stack effect which may occur in a

building, a local buoyancy effect may occur on the fire

floor, in the event of window breakage [60,61] or open doors

to the burn-room. Outside air would enter a door opening

through the bottom and exit through the top. For a door

opening 2 meters (6 feet) high (with a neutral plane at midheight) and with a burn room temperature of 871 °C (1600 °F)

the pressure difference given by equation (A2) is 4.1 Pascals

(0.02 in. W.G. )

.

A. 2. Pressure Differences Due to Restriction

of Volume Expansion

The volume output from a fire depends on the ratio of

the absolute fire temperature to absolute ambient temperature.

If the fire temperature reaches 1151 K (2059 °R) and the

ambient room temperature is 294 K (529 °R) , the effect of

the temperature increase can represent a four-fold expansion

of gas at room temperature. If there is no outflow from the

30
burn-room the pressure will increase four-fold. If there is

volume outflow from a fire the average pressure due to the

outflow is given [18] :

2.5 x 10 T < P < 1.0

where AP is the pressure difference in Pascals

T is the burn-room temperature (K)

T

q

is the ambient room temperature (K)

A is the area of the opening in m2

OR is the burning rate in kg/min.

The inequality represents a range of air to fuel ratios

which occur in different fires. The above shows that the

pressure difference across the outlet of a burn-room is

directly proportional to the absolute temperature and the

square of the burning rate, and inversely proportional to

the square of the burn-room outflow area.

In a fully developed room fire, with a burning rate of

4.55 kg/min (10 lb/min) and the upper air temperature at

870 °C (1600 °F ) , a 1.84 m2 (20-ft 2

) doorway opening will

have a pressure difference of 0.037 Pascals (0.00015 in.

W.G.) to .147 Pascals (0.0006 in. W.G.): A 0.018 m

2 (2 ft 2

) small window opening can have a pressure difference of 3.7

Pascals (0.015 in. W.G.) to 14.7 Pascals (0.06 in. W.G.)

across the window opening.

Because of viscosity the wind velocity profile on the

windward side of the building is of a boundary layer type

[61] . The outside wind velocity will produce a pressure

gradient, which is positive from outside the building to

inside the building on the windward side, and the reverse on

the leeward side. This sets up a horizontal movement throughout the building. The magnitude of this movement depends on

the flow paths into and within the building, the wind speed,

and wind direction. The wind speed and direction are variable.

In references [60] and [61] statistical data for wind properties are available.

A. 3. Pressure Difference Due to Wind

Velocity and Wind Direction

31
The wind pressure gradient can be calculated according

to the following formula [2]

V 2 20.16T (A4)

where V is the velocity (meters per minute)

T is the temperature (K)

AP is the pressure difference (Pascals)

For example if there is a 396 m/min (1320 ft/min) wind

and the temperature is 273 K (459 °R) the wind pressure

generated is 25 Pascals (0.1 in. W.G.). Thus, it appears

that when the height of the fire is small and the burn-room

door is open, the order of magnitude of the pressure difference due to the stack effect (both local and global) and

wind pressure are much larger than the pressure difference

due to volume output of the fire and the buoyant force

between the smoke and ambient air [5,6,7,18,39,4].

Other authors have discussed the buoyant forces including the stack effect and overpressure due to fire [60,61].

For further discussion of these factors the reader is

referred to these papers.

A. 4. Pressure Differences Caused by Air Handling Systems

So far we have discussed natural buoyancy and fire

induced pressure effects. These forces cause smoke to move

throughout a building during a fire, through cracks, openings and vertical shafts. With the HVAC system turned off,

smoke can also move through the duct system by stack action

and buoyancy pressures, to infiltrate the remainder of the

building [50,62]. If the HVAC system is in operation, smoke

will be taken into the return air duct system and move

throughout the building under the system pressure, [50,60,

62] . The HVAC system can either move smoke throughout the

building or be used to control smoke movement. By creating

areas where the pressure is greater than the buoyancy and

stack pressures discussed previously, the smoke can be kept

out. By creating areas of low or negative pressure smoke

can be made to exhaust. Various arrangements of controls

for smoke movement are discussed in references [17,61]. The

subsequent sections in this report will discuss both field

tests and analytical procedures used to measure and predict

the pressure developed by various control systems.

32
Building leakage may play a very significant part in

the pressure gradients affecting smoke movement in leaky

buildings [14]. In tightly constructed buildings, the air

handling system more than compensates for the possible

leakage of air into and out of a building due to the stack

effect. In other words, these buildings can be considered

air tight with the makeup flow generated by the air handling

system. Although there is no perfectly airtight building,

one can compensate for small amounts of leakage with the

makeup air supply from the air handling system. With a leaky building, the HVAC system may require supplementary

capacity to make up for the air leakage.

33
REFERENCES

[1] Tamura , G. T. , Experimental Studies on Pressurized

Escape Routes, ASHRAE Transactions, Vol . 80, Part 2,

p. 224-237 (1974).

[2] Tamura, G. T. , and Shaw, C. , Air Leakage Data for the

Design of Elevator & Stair Shoot Pressurization Systems.

[3] Tamura, G. T. , Air Leakage Measurements of the Exterior

Walls of Tall Buildings, ASHRAE Spring Conference,

Minneapolis (May 1973) .

[4] McGuire, J. and Tamura, G. T. , Fire and Leakage Tests

of Dampers for Smoke Shafts, NRC, Division of Building

Research, DBR Internal Report No. 428 (Apr. 1976).

[5] Tamura, G. T. , Analysis of Smoke Shafts for Control

of Smoke Movement in Buildings, ASHRAE Transactions,

Vol. 76, Part 11, p. 290-297 (1970).

[6] Wakamatsu, T. , Smoke Movement in Buildup - Field

Experiments in Welfare Ministry Building and Analysis

of Sennichi Building Fire, Occasional Report of

Japanese Association of Fire Science and Engineering

No. 1 (1974)

.

[7] Imazu, H. , Smoke Evacuation Effect by Forced Air into

High Rise Buildings from Main Reports on Production,

Movement, and Control of Smoke in Buildings, Occasional

Report of Japanese Association of Fire Science and

Engineering

.

[8] Moulen, A., Control of Smoke from Fire in an Airconditioned Building TR 44/153/410 Department of Works,

Commonwealth Experimental Building Station, North

Hyde, N.S.W. 2113, Australia.

[9] Moulen, A. , Fire Precaution in Buildings with Air

Handling Systems, Paper 18 in the CIB Symposium on the

Control of Smoke Movement in Building Fires held by

the Fire Research Station, Garston Watford, U.K. (Nov.

1975)

.

[10] Butcher, E., Cottle, T. and Bailey, T., Smoke Tests in

the Pressurized Stairs and Lobbies of a 26-Story

Office Building, Building Services Engineer, Vol. 39,

p. 206-210 (Dec. 1971)

.

34
[11] DeCicco, P. , Cresci, R. and Correale, W. , Fire Tests,

Analysis, and Evaluation of Stair Pressurization and

Exhaust in High-Rise Office Buildings, Polytechnic

Institute of Brooklyn Center for Urban Environmental

Studies (Baywood Publishing Company, New York, 1973).

[12] DeCicco, P. , Smoke and Fire Control in High-Rise Office

Buildings - Part 1: Full Scale Tests for Establishing

Standards, ASHRAE Symposium on Experience and Applications on Smoke and Fire Control, Louisville (June 24-

28 1973) .

[13] Zinn, R. , Bankston, C., Cassanova, R. , Powell, E. and

Koplon, N. , Fire Spread and Smoke Control in High-Rise

Fires, Fire Technology, Vol. 10, No. 1 (Feb. 1974).

[14] Fung, F. , Smoke Control by Systemmatic Pressurization,

Fire Technology, Vol 11, No. 4 (Nov. 1975).

[15] Fung, F. and Ferguson, J. , Test and Evaluation of the

Smoke Control Features of the Seattle Federal Building,

Proceedings of the Public Buildings International

Conference on Fire Safety in High-Rise Buildings

(Nov. 1974)

.

[16] Roth, L. , Fung, F. and Zile, R. , NBSIR, Work in Progress

[17] Fung, F. , Preliminary Smoke Movement Studies of Two

Buildings at Goddard Space Flight Center, National

Bureau of Standards (U.S.) (May 1976).

[18] Fung, F. , Evaluation of a Pressurized Stairwell Smoke

Control System for a Twelve Story Apartment Building,

National Bureau of Standards, (U.S.), NBSIR 73-277

(June 1973)

.

[19] Fung, F. and Zile, R. , San Antonio Veterans Administration Hospital Smoke Movement Study, National Breau of

Standards (U.S.)., NBSIR 75-903 (Nov. 1975).

[20] Fung, F. and Zile, R. , Test and Evaluation of the Smoke

Control Capabilities of the San Diego Veterans Administration Hospital, National Bureau of Standards (U.S.),

Work to be Published.

[21] Roth, L. , Fung , F. and Zile

,

R. , NBSIR, Work in Progress

[22] Roth, L. , Fung, F. and Zile

,

R. , NBSIR, Work in Progress

35
[23] Fung, F. and Fothergill, J. W. , Smoke Control Design by

Application of Computer Simulation Technology, ASHRAE

Semiannual Meeting, Chicago, 111. (Feb. 1977).

[24] Fothergill, J. W. , Fothergill, P.A. and Johnson,

M.A. , Development of an Air Movement Simulation

Program, Integrated Systems, Inc., Final Report,

Contract No. 5-35727, National Bureau of Standards

(Nov. 1975)

.

[25] Fothergill, J. W. , et al . , Air Movement Computer

Program Manual, Contract No. 5-35727, Task Report,

National Bureau of Standards (Nov. 1975)

.

[26] Fothergill, J. W. , et al . , Air Movement Computer

Program - Users Manual, National Bureau of Standards,

Contract No. 5-35727, Task Report (Nov. 1975).

[27] Fothergill, J. W. , et al.. Validation Testing of New

Air Movement Program Using the Rouse-Wates Building

Field Test, National Bureau of Standards, Contract No.

5-35717, Task Report (Nov. 1975).

[28] Fothergill, J. W. , et al . , Field Test Comparison and

Parametric Analysis San Diego Veterans Administration

Hospital, National Bureau of Standards, Contract No.

5-35727, Task Report (Nov. 1975).

[29] Fothergill, J. W. , et al . , Comparison of Field Trace

Gas Test Data of the Chicago Veteran's Hospital

(The Hines Building) with Computer Simulation Data,

National Bureau of Standards, Contract No. 5-35727,

Task Report (Nov. 1975) .

[30] Fothergill, J. W. , et al . , Comparison of Field Trace

Gas Test Data of Building 22 - NASA Goddard Space

Flight Center with Computer Simulation Data, National

Bureau of Standards, Contract No. 5-35727, Task

Report (Nov. 1975)

.

[31] Fothergill, J. W. , et al . , Calibration of a Parametric

Computer Model of the Air Movement of the Seattle

Federal Building, National Bureau of Standards,

Contract No. 5-35727, Task Report (Nov. 1975).

[32] Sander, D. and Tamura, G. , A Fortran IV Program to

Simulate Air Movement in Multi-Story Buildings, National

Research Council of Canada, Ottawa DBR Computer

Program No. 35 (Mar. 1973).

36
[33] Barrett, R. and Lochlin, D., A Computer Technique for

Predicting Smoke Movement in Tall Buildings, Symposium

on the Control of Smoke Movement on Escape Routes in

Buildings, Hertfordshire, England (Apr. 1969).

[34] Maeda , T. , et al . , Mixing of Smoke and Air at the Interface of Two Layer Flame in Main Reports on Production

Movement and Control of Smoke in Buildings in Occasional

Report of Japanese Association of Fire Science and

Engineering No. 1 (1974).

[35] Terai, T. , et al . , Richardson Number at the Interface

of Smoke Air Stratified Flows in Main Reports on

Production Movement and Control of Smoke in Buildings

in Occasional Report of Japanese Association of Fire

Science and Engineering, No. 1 (1974).

[36] Wakamatsu, T. , Calculation of Smoke Movement in

Buildings, Occasional Report of Japanese Association

of Fire Science and Engineering (1974)

.

[37] Wakamatsu, T. , Calculation Methods for Predicting

Smoke Movement in Building Fires and Designing Smoke

Control Systems, ASTM-NBS Symposium, Washington, D.C.

(Mar. 1976)

.

[38] Wakamatsu, T. , Unsteady Calculation of Smoke Movement

in an Actually Fired Building, CIB Symposium on the

Control of Smoke Movement in Building Fires, Vol . 1,

Held by the Fire Research Station, Building Research

Establishment at Garston, Waterford, England

(Nov. 4-5, 1975).

[39] Evers, E. and Waterhouse, A., A Computer Model for

Analyzing Smoke Movement in Buildings, Scientific

Control Systems Limited, London WIP 4AQ (1974).

[40] Cresci, R. , Smoke and Fire Control in High-Rise Office

Buildings - Part II: Analysis of Stair Pressurization

Systems, ASHRAE Symposium on Experience and Applications on Smoke and Fire Control, Louisville (June 24-28,

(1973)

.

[41] Tamura, G. and Wilson, A., Natural Venting to Control

Smoke Movement in Buildings via Vertical Shafts,

ASHRAE Transactions, Vol. 76, Part II, p. 279-289

(1970)

.

[42] McGuire, J. , Tamura, G. and Wilson, A., Factors in

Controlling Smoke in High Buildings, ASHRAE Symposium

Bulletin Fire Hazards in Building, p. 8-13,

San Francisco (Jan. 1970).

37
[43] Hutcheson, N. and Shorter, G. , Smoke Problems in

High Rise Buildings, ASHRAE Symposium on Fire Hazards

in Buildings and Air Handling Systems, Lake Placid,

N.Y. (June 24-26, 1968).

[44] Fung, F., Evaluation of Smokeproof Stair Towers and

Smoke Detector Performance, NBSIR 75-701 (Sept. 1975)

.

[45] Ken'jishi, N. and Kuroda , Y. , Model Test of Smokeproof Tower Under Enforced Heating, Shobo Kenkyojo

Hakoko (31) p. 35-43 (1970)

.

[46] Imazu, H., Inflatable Smoke Shutters in Main Reports

on Production Movement and Control of Smoke in Buildings

from Occasional Report of Japanese Association of Fire

Science and Engineering, No. 1 (1974).

[47] Imazu, H. , Inflatable Smoke Barriers to Enclose Stairs,

Hall Devised by Tokyo, F.D. Science Lab, Fire Engineering, Vol. 127, No. 12, p. 36-38 (1974).

[48] Imazu, H. , Inflatable Shutters for Stopping Smoke

Spread, Fire, Vol. 67, No. 838, p. 553-561 (Apr. 1975).

[49] Tamura, G. , Computer Analysis of Smoke Movement in

Tall Buildings, ASHRAE Transactions, Vol. 75, Part II,

p. 81-92 (1969)

.

[50] Tamura, G., McGuire, J., and Wilson, A., Air Handling

Systems for Control of Smoke Movement, ASHRAE Symposium

Bulletin, Fire Hazards in Buildings, San Francisco,

Calif., p. 14-19 (Jan. 1970).

[51] Tamura, G. and McGuire,' J. , The Pressurized Building

Method of Controlling Smoke in High Rise Buildings,

National Research Council of Canada, Division of Building Research, Technical Paper No. 394, Attawa (Sept.

1973)

.

[52] Fung, F.C.W., A Guided Tour on Smoke Control by

Systematic Pressurization ASHRAE Symposium, Washington,

D.C., (Dec. 1975).

[53] Butcher, E., The Design of Pressurization Systems - A

Survey of Current Codes and Discussions of Difficulties,

CIB Symposium on the Control of Smoke Movement in

Building Fires, Vol. 1, Held by the Fire Research

Station, Building Research Establishment at Garston,

Waterford, England (Nov. 4-5, 1975).

Lie, T. and McGuire, J. , Control of Smoke in High-Rise

Buildings, First European Conference of NFPA, Geneva

(Oct. 15-17, 1973). 38

[ 54 ]
[55] McGuire, J. and Tamura, G. , Simple Analysis of SmokeFlow Problems in High Buildings, Fire Technology,

Vol . 11, No. 1, p. 15-22 (Feb. 1975).

[56] Shaw, C. and Tamura, G. , A Design of a Stairshaft

Pressurization System for Tall Buildings, ASHRAE

Journal, Vol. 18, p. 29-33 (Feb. 1976).

[57] Erdelyi, B. , Test Results of a Ducted Stairwell

Pressurization System in a High-Rise Building,

Symposium on Fire Technology Developments that Affect

the ASHRAE Engineer, ASHRAE Semiannual Meeting,

Atlantic City, N.J. (Jan. 26, 1975).

[58] Foulquire, J. , Safety Against Fire, Tall Buildings,

Smoke Clearing, Circular of, Paris (June 7, 1974).

[59] Riou, Col. J. , Smoke Extraction Buildings, A

Solution, Fire International, Vol. 37, p. 41-59

(1972).

[60] Heselden, A.J.M. and Baldwin, R. , The Movement and

Control of Smoke as Escape Routes in Buildings,

Vereinigung Zur Forderung des Deutschen Brandschutzes

E.U. (Mar. 1975).

[61] Hobson, P. and Stewart, L. , Pressurization of Escape

Routes in Buildings, Heating and Ventillating Research

Association, Brachnell, Berkshire, England (Jan. 1973)

[62] Tamura, G.T. , Computer Analysis of Smoke Control with

Building Air Handling Systems, ASHRAE Journal, Vol. 14

No. 8, p. 46-59 (Aug. 1972).

39
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. 1. BIBLIOGRAPHIC DATA

SHEET

4. TITLE AND SUBTITLE

PUBLICATION OR REPORT NO. 2 NBSIR 77-1209Gov’t Accession 3 No.

5

. Recipient’s Accession No.

. Publication Date Control of Smoke Movement in Buildings: A

7. AUTHOR(S)

I. A. Benjamin, F. Fung and L. Roth

9. PERFORMING ORGANIZATION NAME AND ADDRESS

Review April 1977

6. Performing Organization Code

8. Performing Organ. Report No.

10. Project/Task/Work Unit No.

12

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

4900900

11. Contract/Grant No.

. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

Same as No. 9 Final Report

14. Sponsoring Agency Code

15.

SUPPLEMENTARY NOTES

This paper was originally presented at the UJNR Conference (United States & Japan

Panel on Natural Resources) in Tokyo, Japan (BRI) on October 21, 1976.

16.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

A state-of-the-art review of efforts in smoke movement and smoke

control is presented. Basic principles, experimental techniques and

results, computer models, and smoke control methods which have been

employed are presented. The paper covers all work in the area of

smoke movement and smoke control but emphasizes the work of NBS

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)

gas ^c principles; computer calculations; computer modeling;

experimental methods; smoke control methods; smoke movement; smoke

simulation; state-of-the-art review.

18. AVAILABILITY Unlimited

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2* Gov c Accession

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3. Rccipiei 's Accession No.

4. TITLE AND SUBTITLE

Development, Testing end Evaluation of MHD-Materials

5. Publication Date December 31, 1976

6. Performing Organization Codi

7,fre^erxkse, Negas and Schneider

8. Performing Organ. Report No

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON. D.C. 20234

10. Project/Task/Work Unit No. 3130407

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Energy Research and Development Administration

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Covered

Oct. -Dec. 1976

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15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Much time and effort during this first Quarter of

FY 77 has been devoted to the coordination of electrode/insulator tests in various MKD

facilities. This involved close collaboration with a number of MHB-contraetors acid sux contractors with respect to the procurement of materials, the design of electrcde/insu]

tor assemblies , as well as the planning and information of actual running conditions,

NBS is participating in a number of test series: the U-02 experiments, the ANL/Reynclc

screening tests for U-25 electrodes, the recently initiated accelerated program of elec

trode testing in the MIT rig, as well as the AVCO program on materials for slagging cor ditions. A considerable number of tested electrode assemblies were received by NBS;

these are being analyzed and evaluated using optical microscopy, x-ray diffraction and

3EM techniques. Valuable information was obtained concerning the durability of various

electrode materials and the possible causes of degradation. Two major problems address

during this reporting period were: a. The fabrication of relatively thin layers (l-4mm)i

of spinel, zirconia and chromite by means of arc plasma spraying and, b. The joining of

ceramics to metal-alloy leadouts. Because of the heavy emphasis on Materials Testing a Characterization (Task K) , work in other areas was somewhat reduced. Progress on other

tasks included: 1. Viscosity was determined of some slag (Illinois #6) obtained from t

UTSI MHD-channel. 2. Additional data were obtained relevant to the interaction of seed

and slag. 3. A thorough investigation was made of reaction layers on Corhart X-317 Cera

nd.es. exposed to flyash and seed in the test rig of the Fluidyne Eng. Corp. 4. A number

of new and modified spinels were prepared and electrical conductivities of these materi

to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

"

\

:

'

• " r •'

' : . i

' : AVCO; electroda/insulator; magnetohydrodynamics ; U-02 - -

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