Fire in high buildings

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Fire in high buildings

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NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH

FIRE IN HIGH BUILDINGS by

M.

Galbreath F i r e Study No. 2 1 of

the

Division of Building R e s e a r c h OTTAWA April 1968

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FIRE

IN HIGH BUILDINGS by

M. Galbreath

During the l a s t few y e a r s there has been a significant in- c r e a s e in the number of high buildings erected in Canada. The tallest of these to date i s 56 storeys, or 736 f t high. Such bui1ding.s introduce problems in f i r e safety that a r e different in degree and type f r o m those encountered in m o r e traditional buildings, s o that safety m e a s u r e s based on accumulated experi- ence alone cannot be expected to cover all.innovations in design.

In the hope that the r e c o r d of f i r e s in high buildings would give s o m e indication of the kind of incident that might occur, a study was undertaken of r e p o r t s of f i r e s that have occurred since 1950. A high building in this context was assumed to b e one 6 s t o r e y s o r over in height.

The m o r e common f i r e department a e r i a l ladders generally r e a c h about 80 f t above ground, or about the level of the 6th o r 7th floor. If a f i r e occurs in a floor above this level effective m e a s u r e s to control i t and r e s c u e occupants m u s t be conducted within the

building. I t may a l s o be n e c e s s a r y for those in the upper p a r t of the building to p a s s through a f i r e floor on their way to a place of safety. Evacuation of a tall building may involve moving a l a r g e number of people, for l a r g e r buildings may contain m o r e than

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References to r e p o r t s of f i r e s in high buildings that have occurred since 1950 a r e included in Appendix A. Most of these have appeared in the published literature; a few a r e the r e s u l t of v i s i t s by DBR staff to building f i r e s . About 60 per cent of the f i r e s occurred in buildings erected since 1950.

The occupancies of the buildings involved w e r e residen- tial ( l o ) , office ( l o ) , department s t o r e s (3), and hospital (1). The deaths of ninety-seven people occurred in s i x of the f i r e s , the majority in residential buildings. The l a r g e s t l o s s of life in one f i r e occurred in a penthouse r e s t a u r a n t where 25 people died. In the office buildings most of the f i r e s occurred when the buildings were occupied only by c l e a n e r s and maintenance staff, and this contributed to the low loss of life in these occupancies. Table I shows the buildings and floors on which deaths occurred.

The figures r e p r e s e n t f i r e s in which l a r g e l o s s of life o r property occurred. Smaller f i r e s a r e not usually reported. The numbers a r e therefore not particularly significant, but the r e p o r t s may be assumed to illustrate the types of incident that have occurred. Some of the interesting f e a t u r e s of these f i r e s a r e discussed below.

2 . SPREAD OF FIRE BETWEEN COMPARTMENTS

Limits can be placed on the extent of probable f i r e spread by dividing a building into a s e r i e s of fire-tight compartments. In a m u l t i - s t o r e y building i t i s d e s i r a b l e that each floor should be

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a separate compartment. In high buildings the involvement of two or m o r e floors may p r e s e n t v e r y considerable problems f o r f i r e fighters. In addition, the possibility of f i r e s p r e a d f r o m one floor to another c a r r i e s with i t the possibility of successive spreading to other floors, thus involving the whole of a building above the floor initially on f i r e . Typical f i r e incidents a r e

related to the buildings in which they occurred in Table 11, which shows that spread of f i r e to upper floors occurred five times by exterior windows, f o u r times by s t a i r o r escalator, and four times by v e r t i c a l shafts, one of these a refuse chute.

In one building spread of f i r e to the floor above by way of an exterior window occurred although there was a masonry spandrel 4 f t

-

9 _in. _{high between successive windows. In three}

of the examples noted there was combustible ceiling tile adjacent to the windows. This may have contributed to the s i z e of f l a m e outside the windows, and would provide a readily ignited surface behind the windows on the next floor. I t i s a l s o noted that a l l these incidents of spread of f i r e through windows occurred in the upper half of the building. The a i r p r e s s u r e s in the building (discussed in Section 3, Spread of Smoke and Toxic Gases) may have contributed to g r e a t e r flaming outside the windows.

Vertical spread of f i r e by s t a i r s occurred in older buildings (1922 and e a r l i e r ) , except for one built in 1956 and l a t e r converted f r o m an apartment building to a hotel. The m o r e modern design of s t a i r s with self -closing doors and non-combustible interior finishes may be l e s s likely to spread f i r e .

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Spread of f i r e in shafts i s common even in modern buildings. These shafts may be a s much a s 250 sq f t in a r e a and contain air-conditioning ducts, chilled water, fuel pipe lines and electrical bus bars. Insulation and pipe wrapping contribute a significant quantity of combustible and, in some c a s e s , high f l a m e spread materials.

3 . SPREAD O F SMOKE AND TOXIC GASES

I t i s possible that the g r e a t e s t danger to life in building f i r e s l i e s in the smoke and toxic gases produced. Even s m a l l

quantities of combustible m a t e r i a l s can produce l a r g e quantities of smoke. Although i t may be possible to limit some of these

sources, i t may be that m o r e s u c c e s s can be achieved by controlling the movement of smoke.

I t has been demonstrated by Tamura and ~ i l s o n " ) that quite considerable p r e s s u r e differences exist in high buildings. This tends to f o r c e a i r in a t the bottom and out a t the top of the building under weather conditions resulting in outdoor temperatures lower than those inside the building. I t a l s o c r e a t e s an upward draught in a l l v e r t i c a l shafts such a s s t a i r s and elevators. The p r e s s u r e difference i s related to the height of the building, the a i r tightness of the exterior walls and to the difference in temperature between inside and outside.

These p r e s s u r e s a c t to draw smoke and toxic g a s e s up

through high buildings, a s has been demonstrated by the f i r e reports. Of the 24 f i r e incidents described in Appendix A there w e r e

16

in which

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smoke o r f l a m e travelled up through the building by v a r i o u s paths.

3 . 1 Spread of Smoke by Way of S t a i r s

T h e r e is s o m e possibility that smoke will e n t e r s t a i r s through the c r a c k s that e x i s t around doors. If the d o o r s a r e opened this possibility becomes v e r y much g r e a t e r . The f i r e r e p o r t s in Table I1 show four instances of smoke being drawn into s t a i r s . Causes noted include d o o r s wedged open, doors held open by f i r e m e n s ' hose, and doors opening and closing a s occupants leave. In many buildings i t i s not possible f o r f i r e m e n to lead a hose to a f i r e a r e a except by passing i t through the stairwell. Some f i r e d e p a r t m e n t s a l s o m a k e i t a standard p r a c t i c e to p a s s h o s e s through the s t a i r s .

Spread of Smoke in Shafts

S e r v i c e shafts a r e v e r y often open f r o m b a s e m e n t to roof.

In s o m e buildings f l o o r s a r e c a r r i e d a c r o s s t h e s e shafts a t intermediate f l o o r s . I t is common, however, f o r gaps to be left around pipes

and ducts a t these points. In eight of the examples noted in Table I 1 t h e r e was v e r t i c a l movement of smoke o r f l a m e s in the shafts.

3.3 _{Spread of Smoke by Air -Handling Equipment}

Circulation of a i r through many f l o o r s by a i r handling equipment i s a comparatively r e c e n t development. The older high buildings w e r e heated by s t e a m o r hot water and movement of a i r

was not involved. In one r e c e n t building, however, the a i r conditioning s y s t e m r e c i r c u l a t e s a i r through banks of 10 floors. This type of

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equipment has caused v e r y rapid distribution of smoke through a l l floor a r e a s . Table I shows that i t has occurred in four of the building f i r e s described.

Standards for heating equipment include provisions for dampers held open by fusible links. These dampers may limit the spread of flame or hot gases, but they a r e likely to be in- effective if low temperature smoke i s being transmitted. 4. FIRES IN BASEMENT AREAS

F i r e s in basement a r e a s p r e s e n t a particular problem t o firemen. The natural a i r p r e s s u r e s existing in the building tend to d i r e c t smoke and gases upward through the s t a i r s and other shafts. I t i s difficult, therefore, f o r the f i r e m e n to r e a c h the basement level and to locate the c e n t r e of the f i r e in a smoke- laden atmosphere.

There i s a l s o a strong chance that a f i r e can develop un-

observed in what i s usually the l e s s occupied portion of the building, and one where a high f i r e load in the f o r m of storage and waste paper collection can frequently be found. Seven of the f i r e s listed in Table I originated in the basement floor.

5. ELEVATORS

Elevators a r e the principal means of a c c e s s to floors in high buildings. Few people would consider the possibility of walking up or down 50 floors. The natural reaction of the occupants of a high building on hearing a f i r e a l a r m i s to attempt to leave the floor by elevators. The danger involved in this practice i s illustrated by many of the r e p o r t s of f i r e s in Appendix A. In one building i t is reported that firemen used the elevator communication s y s t e m to

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a s k people to leave the elevators and continue their descent by s t a i r s . In a Danish f i r e it is noted that the elevators functioned throughout the f i r e . I t i s a l s o the p r a c t i c e among f i r e m e n t o take the elevator to the floor immediately below the f i r e and then to approach the f i r e by the stair.

There a r e t h r e e instances of elevators stopping out of control a t the f i r e floor:

(a) In a penthouse r e s t a u r a n t f i r e m e n took the elevator to the floor immediately below the f i r e floor; then the f i r e chief attempted to descend. The elevator r o s e instead to the f i r e floor and stopped. A second elevator carrying m o r e firemen a l s o r o s e to the f i r e floor and stopped there. The firemen had to climb out of the elevator and slide down the elevator cables to the basement.

( b ) In a hospital f i r e s i x of the eight elevators in the c e n t r e section stopped. One group of passengers trapped a t the f i r e floor had to climb out of the elevator to the floor above.

( c ) In an office building f i r e one f i r eman died when the

elevator door opened on the f i r e floor. The l a s t incident is reported a s a possible mistake by the f i r e m e n operating the elevator. In

the

two other c a s e s t h e r e was f i r e immediately adjacent to the elevator shaft and i t i s possible that the f i r e caused a s h o r t in the call button or associated wiring, with the r e s u l t that the elevators w e r e called to that floor.

6 .

_{MEANS O F ESCAPE}

The method of designing exit s t a i r s required by the National Building Code a s s u m e s that people will move to ground level in a

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steady s t r e a m . I t can be demonstrated (Appendix B) that this i s impractical and that in some circumstances the s t a i r s will only accommodate about half the occupants of the floor. In this situation t h e r e i s a probability that panic will occur, adding to the danger of the occupants.

7. MEANS OF COMMUNICATION

I t i s apparent f r o m the r e p o r t s of f i r e s that one of the major problems in high buildings i s lack of communication. In one f i r e two-way radios were used by firemen to maintain contact. In other buildings radios have not been effective because of

masking by the s t r u c t u r e or interference.

Another important objective i s to r e a s s u r e the occupants in order to reduce the possibility of panic. On one occasion f i r e trucks were distributed around a building where they could be seen by the occupants, who would then know that firemen were in attendance. This had the effect of reducing the degree of panic. In the Hartford Hospital fire, people leaning f r o m windows beyond the reach of ladders were advised by f i r e m e n using loud h a i l e r s of the b e s t action to take while awaiting rescue.

8. CONCLUSIONS

8.1 F i r e separations now required between floors in high buildings appear to be satisfactory. No failures of floors a r e reported

a p a r t f r o m r e s u l t s of explosions. Weaknesses do occur, however, in windows, open s t a i r s , o r e s c a l a t o r s and in v e r t i c a l s e r v i c e shafts.

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8.2 Accepted methods of designing buildings do not prevent accumulation or movement of smoke. Natural a i r p r e s s u r e s contribute t o drawing smoke up through s t a i r s , elevators and s e r v i c e shafts. Air-moving equipment a l s o i s responsible for distributing smoke through many floors.

8.3 Elevators a r e frequently used by occupants to leave a building in an emergency. There i s c,on.siderable danger in this practice because the elevator may go out of action, be drawn up to the f i r e floor, or be filled with smoke during a fire. The appropriate m e a s u r e s to be taken will depend on whether or not the elevator i s to be used in fire.

8.4 F i r e m e n a l s o u s e elevators to approach a f i r e floor. I t i s unreasonable to expect them to walk up with their equipment. Automatic controls i n t e r f e r e with the efficient u s e of the elevator by firemen and may place them in danger.

8.5 I t i s not possible for a l l the occupants of upper floors to enter the s t a i r s in an emergency. There is, therefore, need for the provision of a safe place of refuge on each floor connected directly to an escape route leading to the outside.

8.6 There is need f o r means of communication between f i r e m e n and occupants and between f i r e m e n on the f i r e floor and those on the ground, both in order to a s s i s t in r e s c u e and firefighting, and to r e a s s u r e the occupants.

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9 . _{MEASURES THAT CAN BE INCORPORATED IN THE DESIGN} OF BUILDINGS

The foregoing examination of the kinds of incident

occurring in high buildings points to a number of a r e a s in which modifications might be made in design.

9.1 Spread of Smoke

Measures should be taken to reduce the spread of smoke through buildings:

(i) Air p r e s s u r e s in stairwells and elevators that a r e to be used during a f i r e can be maintained a t about 0.1 in. water gauge above that in the surrounding a r e a s . This i s described m o r e fully by ~ c ~ u i r e " ) and should be effective in keeping

shafts f r e e of smoke.

(ii) Alternatively, a lobby provided with either artificial ventilation or an opening to the outside a i r may be placed between each floor a r e a and the s t a i r or elevator. This i s included in the British Standard Code of P r a c t i c e for High ~ l a t s ' ~ ) where a

15-sq-ft opening i s specified. An openable window appears to be accepted in Britain a s an alternative to a permanent opening. Experiments on smoke movement in s t a i r s have been conducted in and in Los Angeles (5). These show that ventilated lobbies and positive a i r p r e s s u r e s can contribute to a smoke- f r e e stair. The NFPA Building Exits a l s o describes,

but does not require, a smoke-proof tower. This i s a s t a i r approached b y a balcony or ventilated space.

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(iii) Service shafts may be sealed a t each floor, using non- combustible m a t e r i a l s to prevent transmission of smoke, o r they may be provided with a vent a t the top t o draw smoke out of the shaft. Shafts differ f r o m s t a i r s in that they a r e not occupied s o that the presence of smoke i s not objectionable provided i t does not enter the floor

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a r e a s . This a l s o i s r e f e r r e d to by McGuile

.

(iv) Smoke and gas detectors should be provided in a i r moving systems to c l o s e dampers and shut off fan m o t o r s when smoke e n t e r s the system. The National F i r e has provisions for smoke detectors in these systems.

(v) Basement a r e a s and other windowless floors should be provided with ventilation openings a t high level o r ducts that may be operated by firemen to c l e a r smoke.

9 . 2 Place of Refuge

Every floor in a high building, including ground floor and basements, should be divided horizontally into compartments by a 1 -hr f i r e separation. This would provide a place of refuge on each floor f o r a l l the occupants of the floor. I t would a l s o provide an a r e a that could be used for firemen to assemble before

entering the f i r e a r e a . I t is, of course, essential that each place of refuge thus formed i s connected to s t a i r s and elevators.

The provisions now in the National Building

ode'^)

f o r smoke-stop doors in hospital buildings would have somewhat the s a m e effect. What i s termed a "horizontal exitn in the National

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Building Code is a l s o recognized therein a s an alternative means of escape.

Some examples of how this suggestion could be implemented a r e illustrated in F i g u r e s 1, and 2, which show typical plans of high buildings and the suggested means for improving f i r e safety.

The partitions do not need to be in the s a m e position on each

floor. They can be placed to minimize interference with the n o r m a l u s e of the floor a r e a . I t can be seen that this provides many

additional exit routes f r o m any point on the floor. 9.3 Elevators

One or m o r e elevators should be assigned for the emergency u s e of f i r e m e n to enable them to approach the fire. These elevators

should have a keyed switch to cut out the automatic controls. They should operate in a smoke-free shaft using positive a i r p r e s s u r e s , a s noted in Section 9.1 (i), and open to a smoke- and f i r e - f r e e lobby. This system has been adopted in Britain and i s illustrated in

Figure 3. The British Code of P r a c t i c e a l s o specifies load and speed of the elevator.

One or two elevators assigned to f i r emen could be used f o r evacuation of a number of occupants. I t i s obvious, however, that if a l l the occupants a r e to be moved by elevator the time to evacuate would be a m a t t e r of hours. The c o s t of enclosing a l l the elevators and lobbies in a f i r e separation would not be much higher than that of protecting one o r two. This would allow a l l the elevators to be used for evacuation in safety.

If

a l l these elevators w e r e to operate under emergency power, however, the additional c o s t might be excessive.

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9.4 Emergency Power

If reliance i s to be placed on fans to c r e a t e smoke-free a r e a s and if elevators a r e to be used for transporting occupants and firemen, emergency power would have t o be provided.

P r e s e n t requirements of the National Building Code cover emergency power only for lighting and exit signs.

9.5

Communications

Many l a r g e buildings now have equipment t o provide back- ground music in public a r e a s and some apartment buildings have two-way communication between apartments and entrance lobby. This could be extended to provide a public a d d r e s s s y s t e m to the occupants, and to introduce some f o r m of two-way communication between ground floor and upper floors.

Spread of F i r e by Windows

Some consideration should be given to the design of windows to reduce the probability of v e r t i c a l spread of fire. This might involve r e s t r i c t i o n s on the s i z e or placing of windows and on the u s e of combustible ceiling finishes.

REFERENCES

(1) Tamura, G.

T.

and A. G. Wilson. P r e s s u r e differences f o r a nine-stor ey building a s a r e s u l t of chimney effect and

ventilation s y s t e m operation. ASHRAE, Transactions, Vol. 72, P a r t I, 1966, p. 180-189 (NRC 9467).

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(2) McGuire, J.

H.

Control of s m o k e in building f i r e s . F i r e Technology, Vol. 3, No. 4, November 1967. (3) B r i t i s h Standard Code of P r a c t i c e . CP3 Chapter IV,

P r e c a u t i o n s Against F i r e . P a r t 1, F i r e precautions

in f l a t s and m a i s o n e t t e s over 80 f t i n height. B r i t i s h Standards Institution, London 19 62.

(4) Col. Beltramelli, Capt. Clement and J. P. F a c k l e r . P r o b l e m s r a i s e d by smoke in f i r e s i n tall blocks of flats. F i r e International, 1 July 19 63 and 2 October 19 63.

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Degenkolb, J. G. Smoke Proof Enclosures. Building Standards Monthly, Vol. XXXV, No. 10, P a r t 1,

October 19 66.

(6) National F i r e Prevention Association. The Building Exits Code, NFPA 101, 1963.

(7) Associate Committee on the National Building Code. National F i r e Code. National R e s e a r c h Council, Ottawa, Canada.

(8) Associate Committee on the National Building Code.

National Building Code 1965. National R e s e a r c h Council, Ottawa, Canada.

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TABLE

I

DEATHS FROM FIRES IN HIGH BUILDINGS

See Occupancy Contributary

Circurns tances

25 Combustible ceiling cut off

I

access to s t a i r . Elevators stopped a t f i r e floor.

-

older* 1

6

1 Smoke passed up v e r t i c a l

I I 9 2 shafts. 10 2 11 12 13

-

P

3

c o r r i d o r . Elevators stopped a t fifth floor.

2 2 Hotel 1898

B

1

9

Explosion damaged f i r s t

2 1 floor. S m o k e passed up

11 1 11 elevatorshafttollthfloor

8

Depar trnent Store older* 7 7 4 W o r k m e n spraying

I 8 3 7 f l a m m a b l e i n s e c t i c i d e o n

caxpets, F i r e passed up

open s t a i r to 8th floor.

7 Hotel older

*

6

4 4 Combustible wall linings

Hospital 1948

B

9

I 16 16 F i r e passed up refuse chute

spread on combustible ceiling tile in

9 th

floor

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TABLE I (conttd)

*

_{older indicates unknown d a t e in e a r l y 1900's.}

**

_{r e c e n t indicates unknown d a t e since about 1950.} Ref. No. S e e Appendix A 17 Occupancy Hotel F l o o r on Which Death Ocur r ed Age of Building 1922 1956

B

13 F l o o r of Origin 1 Hotel Contributary C i r c u m s t a n c e s No. of Deaths on F l o o r 1 2 Not known 2 1 8

Smoke filled stairs

.

No. of Deaths in F i r e Office Office 4 1 12 1 1 1 older* 2 2 2 2

6

3B 3 2 1

Smoke filled s t a i r s and e l e v a t o r shaft. One m a n

I jumped f r o m window and

died.

-

r e c e n t

*

6

2 Smoke p a s s e d up v e r t i c a l 1 shafts. E l e v a t o r opened on f i r e floor.

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S P R E A D O F F I R E BY WINDOWS S P R E A D O F F I R E BY STALRS OR ESCALATORS SPREAD OF SMOKE BY STAIRS S P R E A D O F F I R E BY SHAFTS S P R E A D O F SMOKE BY SHAFTS

S P R E A D

O F

SMOKE

THROUGH ELEVATOR

SPREAD O F SMOKE

THROUGH

VENTILATION SYSTEM

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r

E L E V A T O R S

S C l S S O R S

S T A

l

R

-

F I G U R E

l ( a )

T Y P I C A L F L O O R O F

O F F I C E B U I L D I N G

F I G U R E

l ( b )

F I R E

S E P A R A T I O N

F L O O R M O D I F I E D B Y

A D D I T I O N O F P A R T I T I O N

A N D D O O R S

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F I G U R E 2 ( a )

T Y P I C A L A P A R T M E N T F L O O R

F I G U R E 2 ( b )

F L O O R M O D I F I E D T O P R O V I D E

S E P A R A T I O N I N T O T W O A R E A S

V E N T I L A T E D L O B B Y A C C E S S T O

S T A I R S A N D E L E V A T O R S

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BLOCK - T O W E R BLOCK

F I G U R E 3

P L A N O F B R I T I S H H I G H O F F I C E B U I L D I N G

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APPENDIX A

LIST O F FIRES IN HIGH BUILDINGS

Building Involved Reference

(1) Office building under construction F P A Journal, No. 5 1,

London England Oct. 1960, F i r e Protection

Association, Aldermany House, Queen St., London EC4, England. (2) Office building, New York

(3) Hospital, Hartford Conn.

(4) Apartment building, Denrnar k

(5) Office building, Montreal

Institution of F i r e Engineers Quarterly, Vol XXIII, No. 52, Dec. 1963. The Institution of F i r e Engineers, 148 New Walk, L e i c e s t e r , England.

NFPA Quarterly, Vol. 55, Jan. 19 62. National F i r e Protection As sociation,

60 Batteryrnarch St., Boston 10, M a s s .

F P A Journal, No. 58, Jan. 19 63. F i r e Protection As sociation, Aldermany House, Queen St., London EC4, England.

NFPA Quarterly, Oct. 19 63.

National F i r e Protection A s s ociaticn, 60 B a t t e r y m a r c h St., Boston 10, Mass.

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Building Involved Reference

(6) Office building, London England F P A Journal, No.

61,

Oct. 1963. F i r e Protection As sociation, Aldermany House, Queen St., London EC4, England. (7) Hotel, Boston, Maas.

(8) Dept. store, Tokyo, Japan

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Office building, New York

(1 0) Air terminal building under construction, London, England

NFPA Quarterly, Vol. 57, July 19 63. National F i r e Protection Association,

60 Batterymarch St., Boston 10, Mass.

NFPA Quarterly, Jan. 19 64. National F i r e Protection

Association, 60 Batter ymarch St., Boston 10, Mass.

Society of F i r e Protection,

Engineer's Bulletin, April 1966. Society of F i r e Protection Engineers,

60 Batterymarch St., Boston 10, Mass.

F P A Journal, No. 64, Nov. 19 64. F i r e Protection As sociation, Alder many Hous e, Queen St.

,

London EC4, England.

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Building Involved

(1 1 ) Hotel, Jacksonville, F l o r i d a

(12) , Dormitory, Washington, D. C.

(13) Hotel, Ottawa

(14) Dept. s t o r e , Dallas, Texas

(1 5) Apar trnent building, Ottawa (16) Hotel, New York

(17) Hotel, Newark,N.

J.

(1 8) Off i c e building, Tor onto

R e f e r e n c e

NFPA Quarterly, No. 57, April 19 64. National F i r e Protection Association,

60 B a t t e r y m a r c h St., Boston 10, Mass.

The Evening Star, Washington D. C., USA, M a r . 16, 19 64. DBR F i r e Investigation.

F i r e Journal, Vol. 59, May 1965. National F i r e P r o t e c t i o n

As sociation, 60 Batteryrnarch St., Boston 10, Mass.

DBR F i r e Investigation News Bulletin, National

Automatic Sprinkler and F i r e Control Association Inc.

,

No. 224, Jan. -Feb. 1966. 277 P a r k Ave., New York, N. Y. F i r e Journal, May 1966. National F i r e Protection Association, 60 B a t t e r y m a r c h St., Boston 10, Mass. DBR F i r e Investigation.

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Building Involved Refer enc e

(19) Office building under construction. Construction in South Afr ica, Johannesburg, S. Africa Aug. 1966. The Pithead P r e s s

Ltd., 9 1 Mooi St., Johannesburg South Africa.

(20) Office building, New Orleans

(21) Dept. store, BristoAEngland

(22) Hotel, Boston,Mass.

(23) Apartment building, Ottawa (24) Restaurant and apartment

building, Montgomery, Alabama F i r e Journal, July 1966. National F i r e Protection Association, 60 Batterymarch St.

,

Boston 10, Masa.

F P A Journal, No. 73, Dec. 1966. F i r e Protection As sociation, Aldermany House, Queen St., London

EC4,

England.

F i r e Journal, May 19 66. National F i r e Protection

Association, 60 Batterymarch St., Boston 10, Mass.

DBR F i r e Investigation

F i r e News, No. 571, Mar. 1967. National F i r e Protection Associatiq 60 Batterymarch St., Boston 10, Mass.

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APPENDIX B MEANS O F ESCAPE

Building regulations generally contain provisions f o r exits and specify a limit to the number of people per unit exit width (22 in. ). The figures used by the principal North American Codes a r e a l l about the same. They appear to have their

origin in studies conducted by the National Bureau of Standards,

*

Washington in the 1930's.

Studies were made of r a t e of evacuation of a number of buildings and counts w e r e taken of traffic flow through Grand Central Station in New York during r u s h hours. The study con- cluded with recommendations for design of exits based on r a t e of flow of 60 persons per unit exit width per minute through doorways, and 45 persons p e r unit exit width down s t a i r s . The r e p o r t notes that people may be expected to move in a steady flow f r o m low buildings, but that in high buildings this i s not practicable. The figures recommended for high buildings w e r e determined by assuming that the occupants of each floor will stand on the s t a i r s , between the floor they have left and the one immediately below. I t was thought, however, that to provide space for a l l the occupants of each floor to stand in the s t a i r - wells would be uneconomic. I t was therefore suggested that there should be provision f o r

-

half the occupants of each floor above the f i r s t to stand on the stairwells.

*

Design and Construction of Building Exits. Misc. Pub.

M15 1, U. S. Dept. of Commerce, National Bureau of Standards, Washington, 1935.

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**

A m o r e recent study by the London Transport Board has demonstrated how the degree of crowding can affect r a t e of travel. The optimum spacing suggested f o r movement of people in level c o r r i d o r s i s 7 . 7 s q f t p e r person which

corresponds to a forward speed of 2.3 mph (202 f t l m i n ) . For the s a m e speed m o r e width i s needed on s t a i r s than in c o r r i d o r s . An interesting observation, however, i s that local r e s t r i c t i o n s in the corridor, not m o r e than 10 f t in length, can be accom- modated without reduction in speed. Thus i t i s the recommen- dation of the British study that connecting c o r r i d o r s be not l e s s than 213 the width of the s t a i r s and that local reductions in the c o r r i d o r be not l e s s than 1 /2 the width of the s t a i r s .

When the space i s 5 s q f t p e r person on both c o r r i d o r s and s t a i r s the forward speed i s 1.5 mph (132 f t l m i n ) . This appears to be close to that required for emergency exit and corresponds to a r a t e of 40 persons per unit exit width p e r

minute. At 2.5 s q f t p e r person flow i s impeded and a t 2.0 sq f t p e r per son all forward movement stops.

The National Building Code suggests 100 s q f t per person a s the occupancy load of an office floor area. Exit s t a i r s m u s t

**

Second Report of the Operational Research Team on the Capacity of Footways. Research Report No. 95, London Transport Board, London, August 1958.

Also described in:

Information Sheet 1194, Internal Circulation, Architects' Journal, Information Library, 20 March 1963. Architectural P r e s s Ltd.,

9 -

13 Queen Anne1 s Gate, London SW1 England.

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be provided to allow 60 persons per unit exit width (22 in.). There i s a l s o a minimum provision of a t l e a s t two s t a i r s not l e s s than 3 f t wide. A normal s t a i r well might be about

15 f t by 6 f t or 90-sq-ftfloor area.

I

we a s s u m e that people will stand in the stairwell between any floor and the one

immediately below in a floor space of 2 s q f t p e r person each s t a i r will accommodate 45 people. In an office floor a r e a

9,

000 s q f t in a r e a with 90 occupants there will be room on the s t a i r s for everyone to stand. F o r a l a r g e r floor a r e a and a g r e a t e r number of people t h e r e may be insufficient space in the s t a i r s . Figure B-1 shows the r a t i o of people on the floor for office buildings to NBC and standing space in s t a i r s for different a r e a s of floor.