Experimental studies on pressurized escape routes

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Publisher’s version / Version de l'éditeur:

ASHRAE Transactions, 80, 2, pp. 224-237, 1974

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Experimental studies on pressurized escape routes

Tamura, G. T.

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NATIONAL RESEARCH COUNCIL OF CANADA CONSEIL NATIONAL DE RECHERCHES DU CANADA

Experimental Studies on Pressurized Escape Routes

by George T. Tamura Reprinted from ASHRAE Transactions Vol. 80, Part 2,1974 p. 224 - 237

dy permission of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Research Paper No. 631 of the

Division of Building Research

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L'auteur prbsente les resultats d'essais effectubs sur deux edifices en vue d'6valuer I'efficacitb de la pressurisation pour empgcher I'effondrement des puits d'escalier en cas d'incedie. On vbrifie I'effet de garder quelques portes ouvertes et I'effet d'une injection d'air A la base ou au sommet du puits. L'auteur recommande I'injection d'air

_A

plusieurs niveaux afin d'assurer une pressurisation uniforme du puits d'escalier et un 6coulement d'air dans I'ensemble du puits. On presente egalement les donnbes des essais concernant 11btanch6itb

A I'air des murs et des portes des p~lits d'escalier ainsi que la resistance A I'bcoulement A I'intbrieur du puits.

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No. 2319

.GEORGE T. TAMURA

Member ASHRAE

The p r e s s u r i z a t i o n of s t a i r shafts a s a means of providing s m o k e - f r e e e s c a p e routes during a f i r e has received much attention i n recent y e a r s by a number of investigators and code authorities (1-11). This method has special application to high-rise buildings a s evacuation time can be long and f i r e fighting difficult; hence s a f e v e r t i c a l passageways must b e a s s u r e d for the duration of a f i r e . It entails injecting outside a i r into the s t a i r shaft to establish flow f r o m i t to adjacent s p a c e s , thus preventing e n t r y of smoke into the s t a i r shaft as well a s dis- per sing any smoke within it.

The design of a s t a i r p r e s s u r i z a t i o n s y s t e m r e q u i r e s information on the airtightness of walls and d o o r s of s t a i r shafts and on the r e s i s t a n c e to a i r flow through the s t a i r shaft itself. The t e s t s described i n this paper w e r e conducted to obtain this information for two high-rise buildings. It must be anticipated that s e v e r a l s t a i r doors will be open during a f i r e to permit evacuation and f i r e fighting. This reduces the p r e s s u r e s i n the s t a i r shaft and can adversely affect the performance of the smoke control s y s t e m . The effect of having some s t a i r d o o r s open was also checked, therefore, a s well a s the differences that occur when a i r is injected a t the top or,bottom of the shaft.

DESCRIPTION OF BUILDINGS AND TEST PROCEDURE

The s t a i r shaft of building A s e r v e s 23 s t o r i e s (including one basement floor) and has a conventional stairway. The walls of the s t a i r shafts i n building A a r e constructed of c a s t - i n - place concrete. Building B differs i n that its s t a i r shaft s e r v e s 37 s t o r i e s ( 5 of which a r e underground), the s t a i r s a r e the s c i s s o r - t y p e (two s t a i r s i n a single shaft), and the walls of the shaft a r e of concrete blocks. The doors between the s t a i r shaft and the floor s p a c e s a r e the s a m e i n the two buildings. The dimensions of the s t a i r shafts and the buildings a r e given in Table I.

TABLE I

Description of Stair Shafts. Buildings A and B

Building A Building B Building plan 126 ft by 146 f t 107 f t by 146 f t No. of s t a i r shafts 2 2

F l o o r s served above grade 2 2 3 2 F l o o r s served below grade 1 5

Typical floor height 10 f t , 7 in. 11 f t , 6 in. Over - a l l height 258 ft 425 f t

Shaft size 6.75 by 14.25 f t 8. 5 f t by 31.0 ft Typical door size 36 in. by 84 in. 36 in. by 84 in. Construction conventional, s c i s s o r s , c o n c r e t e

cast-in-place blocks, concrete, p l a s t e r paint finish finish

G . T . T a m u r a , N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a , D i v i s i o n o f B u i l d i n g R e s e a r c h , O t t a w a , C a n a d a

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As building A is not provided with a s t a i r shaft pressurization s y s t e m , the t e s t s w e r e conducted using a mobilte fan unit located outside the building entrance and connected to the stair shaft a t ground level by seveGal lengths of aluminum duct. The fan, mounted on a t r a i l e r , i s a vane axial type b i t h variable pitch blades, which p e r m i t variation i n fan flow f r o m z e r o to 50,000 cfm. The flow r a t e of supply a i r was measured with a velocity-pressure averaging tube and s t a t i c p r e s s u r e taps installed i n a duct Gection between the fan and the building.

Building B has a p r e s s u r i z a t i o n s y s t e m f o r each s t a i r shaft, which i s located on the 32nd (mechanical) floor, the top floor. It consists of a vane axial fan, motorized dampers and associated duct-work. E a c h supply fan is r a t e d at 22, 000 cfm at 2. 0 in. of water s t a t i c pressure. Outside a i r is drawn f r o m the cooling tower enclosure and delivered to e a c h s t a i r shaft through a 3- by 5-ft opening in the wall at the 32nd floor. The p r e s s u r i z a t i o n system can be activated either by a pull a l a r m o r a signal f r o m a smoke detector located at the top of each s t a i r shaft.

Initial tests w e r e conducted to determine the airtightness of the s t a i r - s h a f t e n c l o s u r e and the p r e s s u r e l o s s characteristic of the stairway. To isolate a i r leakages through s t a i r doors f r o m those of the wall construction, leakage c r a c k s of a l l s t a i r doors w e r e sealed with tape; the c r a c k s between f r a m e and wall were not sealed. The s t a i r shafts w e r e p r e s s u r i z e d with various supply a i r r a t e s and the concomitant p r e s s u r e differences a c r o s s the shaft walls were measured a t s e v e r a l levels. The t e s t s were conducted with the s t a i r d o o r s sealed followed by t e s t s with them unsealed.

P l a s t i c tubes 1/4 in. in diameter were strung vertically in the s t a i r shaft f r o m the top t e r - minating at s e v e r a l levels s o that the ends of the tube could s e r v e a s p r e s s u r e taps to measure the p r e s s u r e l o s s e s within the s t a i r shaft. The difference i n p r e s s u r e s between each p r e s s u r e tap and the top of the s t a i r shaft was measured with a p r e s s u r e m e t e r (diaphragm type with silicon piezo-resistive gauge; s t a t i c e r r o r band of

*

1. 5% of full-scale output).

T e s t s were conducted with the pressurization s y s t e m s in operation and with the s t a i r and entrance doors open a t o r near grade level. This was followed by a s e r i e s of t e s t s conducted with various combinations of open s t a i r doors. During each t e s t , p r e s s u r e differences across the s t a i r doors, p r e s s u r e l o s s e s within the s t a i r shafts, and the supply a i r rates w e r e measured. In addition, the a i r velocity through each s t a i r door opening was measured with a hot w i r e anemometer. The difference in p r e s s u r e s between outside and the s t a i r shaft at the top and at grade level was also measured to r e l a t e the s t a i r - s h a f t p r e s s u r e s to outside p r e s s u r e s .

RESULTS AND DISCUSSION

The r a t e of a i r supply required to p r e s s u r i z e a s t a i r shaft to a desired level depends upon the airtightness of the shaft enclosure. T e s t s conducted with a l l of the s t a i r doors sealed give the airtightness value of the shaft wall construction, whereas the test conducted with the door s e a l s removed yields the o v e r - a l l airtightness value of the shaft enclosure. The difference in the two readings i s the airtightness value of the s t a i r doors.

The airtightness values in t e r m s of equivalent orifice a r e a in s q u a r e feet per floor were a s follows:

Building A Building B Shaft wall

Stair door

TOTAL 0. 26 0.42

It i s evident that the shaft walls of building A a r e considerably tighter than those of building B. The f o r m e r a r e constructed of cast-in-place concrete, whereas the l a t t e r a r e constructed of concrete blocks. In addition, a number of s e r v i c e panels and pipes in the stair shaft of building B probably contributed to its relatively high leakage value. The airtightness values of the s t a i r doors of buildings A and B, however, were s i m i l a r . This i s consistent with the measurements of the c r a c k widths between door and f r a m e which w e r e s i m i l a r for both build-

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ings with a v e r a g e values of 3/8 in. a t the bottom and 3/32 in. f o r the remaining t h r e e aides.

The r e s i s t a n c e to flow caused by the path i o r m e d by the shaft wall and s t a i r c a s e can affect, the uniformity of v e r t i c a l p r e s s u r i z a t i o n in the s t a i r shaft. T h e p r e s s u r e gradient inside the s t a i r shaft i s a l s o affected by the change i n flow r a t e by leakage flow through the shaft w a l l and the column weight of a i r , assuming that t h e r e i s no t e m p e r a t u r e gradient and that the c r o s s - s e c t i o n a l a r e a of the s t a i r s h a f t i s constant f o r the height of the shaft ( 1 , 2 ) . To mini- mize the effect of the leakage flow, p r e s s u r e l o s s e s of the , s t a i r shaft of building A w e r e m e a s u r e d with a l l s t a i r doors s e a l e d making the shaft wall virtually a i r t i g h t . The p r e s s u r e l o s s e s m e a s u r e d a r e thus due to the flow r e s i s t a n c e of the s t a i r shaft, a s the effect of column weight of a i r i s a l s o eliminated with the u s e of v e r t i c a l r u n s of plastic tubes a s previously described. The s t a i r shaft was p r e s s u r i z e d with supply a i r r a t e s of 9 , 0 0 0 and 18, 000 c f m at g r a d e level with the s t a i r door a t the top level open. The flow r a t e s m e a s u r e d at the entrance and exit of the s t a i r shaft indicated leakage flow through the shaft walls of l e s s than 570 of the supply a i r r a t e s .

The m e a s u r e m e n t of the p r e s s u r e l o s s c h a r a c t e r i s t i c s of the s c i s s o r s t a i r s of building B was not attempted a s i t s shaft walls w e r e found to be quite leaky and hence a r e a l i s t i c value could not be expected. T e s t s w e r e conducted, however, on.the s c i s s o r s t a i r s of ar, l l - s t o r e y building (building C) whose shafts a r e constructed of c a s t - i n - p l a c e concrete. Measurements '

of the a i r t i g h t n e s s of these shaft walls gave leakage values s i m i l a r to those of building A. With the s t a i r d o o r s s e a l e d , the s t a i r shaft was p r e s s u r i z e d with flow r a t e s of 15,000, 20,000 and 25,000 cfm.

The p r e s s u r e l o s s c h a r a c t e r i s t i c s of the s t a i r shafts f o r both buildings A and C w e r e l i n e a r with height; the p r e s s u r e l o s s e s varied with the s q u a r e of the supply a i r r a t e s . Fig. 1 gives the relationship between the supply a i r r a t e s and the a v e r a g e p r e s s u r e l o s s e s p e r f l o o r , f r o m which the p r e s s u r e loss f a c t o r s w e r e calculated. The p r e s s u r e l o s s factor a s defined in this pape'r i s given by the following equation:

w h e r e

K = p r e s s u r e l o s s f a c t o r , per floor

A P

= p r e s s u r e l o s s , in. of water N = number of floors

VH = velocity head, in. of water

The value of VH i s based on the a i r flow r a t e divided by the f u l l c r o s s -sectional a r e a of the conventional s t a i r shaft, and one- half the c r o s s - s e c t i o n a l a r e a of the s c i s s o r s t a i r which con- tains two s e p a r a t e s t a i r w a y s .

The calculation of p r e s s u r e loss f a c t o r s yielded values of 45 and 28 for the conventional s t a i r s h a f t (building A) and the s c i s s o r s t a i r s h a f t (building C) respectively.

The s c i s s o r s t a i r shaft differs f r o m that of the conventional s t a i r in that the s t a i r w a y con- tinues in the s a m e d i r e c t i o n between f l o o r s , w h e r e a s , in the conventional s t a i r shaft the s t a i r w a y makes a 180-deg t u r n mid-way between floors. T h e number of 180-deg t u r n s i n the conventional s t a i r shaft, t h e r e f o r e , would be twice a s g r e a t a s that for the s c i s s o r s t a i r serving the s a m e number of floors. The conventional s t a i r shaft usually h a s no party w a l l at the inner r a i l i n g s , w h e r e a s the s t a i r c a s e of the s c i s s o r s t a i r i s enclosed by a wall on both s i d e s of the tread. The s i z e of the flow channel f o r the s c i s s o r s t a i r i s , t h e r e f o r e , much less than f o r the conventional s t a i r shaft. The values of p r e s s u r e l o s s f a c t o r s c a n facilitate the calculations of p r e s s u r e l o s s e s i n a p r e s s u r i z e d s t a i r shaft. Such calculations a r e n e c e s s a r y i n the design of a s t a i r p r e s s u r i z a t i o n s y s t e m a s high p r e s s u r e l o s s e s within a s t a i r s h a f t can

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r e s u l t in e x c e s s i v e p r e s s u r e d i f f e r e n t i a l s a c r o s s the s t a i r d o o r s , which w i l l i n t e r f e r e with t h e i r operation.

Additional t e s t d a t a a r e r e q u i r e d to d e t e r m i n e the effect of such p a r a m e t e r s a s the s i z e of well between inner r a i l i n g s , d i r e c t i o n of v e r t i c a l flow, and s t a i r c a s e configuration.

Air Injection Into the S t a i r Shaft a t the Bottom (Building A)

F o r a l l of the t e s t s t h e single s t a i r shaft of building A w a s p r e s s u r i z e d with outside a i r sup- plied f r o m the mobile f a n unit ducted to the s t a i r door opening on the ground floor. T h e supply a i r r a t e of 20, 000 c f m w a s b a s e d on the intended u n i f o r m p r e s s u r i z a t i o n of 0. 10 in. of w a t e r a s s u m i n g no p r e s s u r e l o s s e s with a l l but one s t a i r d o o r closed. The outside t e m - p e r a t u r e during the t e s t s was about 50 F.

T e s t No. A1 w a s conducted with the s t a i r and f r e i g h t e n t r a n c e d o o r s on the b a s e m e n t .level open followed by t e s t No. A2 with only the s t a i r door on the 22nd ( m e c h a n i c a l ) floor open. During both t e s t s the building a i r -handling s y s t e m s w e r e in nor ma1 operation. T h e r e s u l t a n t p r e s s u r e difference r e a d i n g s a c r o s s the s t a i r d o o r s f o r both t e s t s , given i n Fig. 2, show that the p r e s s u r e difference p a t t e r n s f o r the two t e s t s differ significantly. F o r test No. A1 the p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s f r o m the f i r s t f l o o r to the 21st floor v a r i e d f r o m 0.10 to 0. 20 in. of w a t e r , w h e r e a s f o r t e s t No. A2 they v a r i e d f r o m 1. 3 t o - 0 . 3 in. of water. The total p r e s s u r e d r o p s inside the s t a i r s h a f t f r o m the f i r s t t o the 22nd f l o o r w e r e 0. 07 and 1 . 6 8 in. of w a t e r f o r t e s t Nos. A1 and A2, respectively.

The nonuniformity of p r e s s u r i z a t i o n can be attributed to the p r e s s u r e L O S S c h a r a c t e r i s t i c

of the s t a i r shaft. T h i s can be significant f o r high flow r a t e s a s in t e s t No. A2 with p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s on the lower f l o o r s that a r e much g r e a t e r than the maximum p e r m i s s i b l e p r e s s u r e difference with r e g a r d to e a s e of door o p e r a t i o n of 0.40 in. of w a t e r (3). With a flow r a t e of 13, 100 c f m through the s t a i r door opening on the b a s e m e n t f l o o r , t h e up- w a r d flow r a t e f o r t e s t No. A1 was'about one t h i r d of t h a t f o r t e s t No. A2 and hence t h e pre- s u r i z a t i o n w a s much m o r e uniform. C r e s c i (2) and Koplon ( 4 ) r e p o r t e d s i m i l a r r e s u l t s f r o m t e s t s conducted on p r e s s u r i z e d s t a i r shafts.

The p r e s s u r e difference of 0. 56 in. of w a t e r a c r o s s the s t a i r d o o r of the 22nd ( m e c h a n i c a l ) floor f o r t e s t No. A1 (point a of F i g . 2) i n d i c a t e s that the p r e s s u r e s on t h i s floor a r e lower than those of the typical f l o o r s by 0.46 in. of w a t e r . T h i s w a s probably caused by p r e s - s u r i z a t i o n on the typical f l o o r s ( 0 . 18 in. of w a t e r ) and s u c t i o n on the mechanical f l o o r (0.25 in. of w a t e r ) with the o p e r a t i o n of the building air-handling s y s t e m s . T h i s would e x p l a i n the negative p r e s s u r e differences a c r o s s the s t a i r d o o r s above the 16th f l o o r f o r t e s t No. A2 a s the s t a i r - s h a f t p r e s s u r e s would tend t o d e c r e a s e and a p p r o a c h those of the mechanical floor with the s t a i r door open on that floor. T h e s e t e s t s indicate that a l a r g e opening a t the top of the s t a i r shaft o r s u b s t a n t i a l mechanical exhaust a t the top with a i r injection at the bottom c a n l e a d t o e x c e s s i v e s t a i r - s h a f t p r e s s u r i z a t i o n a t lower l e v e l s and to inadequate p r e s s u r i z a t i o n a t upper levels.

T e s t No. A3 w a s conducted with the building a i r - h a n d l i n g s y s t e m s s h u t down and with the s t a i r and f r e i g h t e n t r a n c e d o o r s o n the b a s e m e n t floor open. All o t h e r s t a i r d o o r s w e r e closed. With the s t a i r shaft p r e s s u r i z e d the flow r a t e through the open s t a i r door on the basement floor was 14, 200 c f m giving a n upward flow r a t e of 5, 800 cfm i n the s t a i r s h i f t . The p r e s s u r e c h a r a c t e r i s t i c s of t h e two s t a i r s h a f t s , floor s p a c e and outside caused by building s t a c k action and s t a i r - s h a f t p r e s s u r i z a t i o n a r e shown in Fig. 3. T h e horizontal d i s t a n c e s between the s t a i r s h a f t and the floor s p a c e p r e s s u r e c h a r a c t e r i s t i c s r e p r e s e n t the p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s . S i m i l a r l y , the horizontal distances between the floor s p a c e and outside p r e s s u r e c h a r a c t e r i s t i c s r e p r e s e n t the p r e s s u r e d i f f e r e n c e s a c r o s s the e x t e r i o r walls.

The n e u t r a l plane of the building i s located a t about t h e 13th f l o o r , below which the p r e s - s u r e s of the floor s p a c e s a r e higher than t h o s e of s t a i r s h a f t No. 2 ( n o t p r e s s u r i z e d ) and above which the r e v e r s e o c c u r s . T h e p r e s s u r e s of s t a i r shaft No. 1 ( p r e s s u r i z e d ) a r e , a s expected,

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higher than those of the floor s p a c e and outside for the e n t i r e height of the shaft. The p r e s - s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s on the typical f l o o r s v a r i e d f r o m 0. 150 to 0.200 in. of w a t e r , which a r e g r e a t e r than those obtained with the building air-handling s y s t e m s i n n o r m a l operation ( t e s t No. A l j ; the p r e s s u r e d i f f e r e a c e a c r o s s the s t a i r d o o r of the 22nd (mechanical) f l o o r , however, w a s much lower. It would a p p e a r that the h i g h e r leakage r a t e of the shaft w a l l a t this floor with the air-handling s y s t e m s operating probably r e s u l t e d i n p r e s s u r e differences a c r o s s the s t a i r d o o r s of the, typical f l o o r s which w e r e lower than those with air-handling s y s t e m s shut down. .

With injection of untempered outside a i r d u r i n g cold w e a t h e r , the s t a i r -shait t e m p e r a t u r e s can be much lower than those of the surroundings. To investigate t h i s , a i r t e m p e r a t u r e s of s t a i r shaft No. 1 w e r e m e a s u r e d a t s e v e r a l l e v e l s one-half hour after the s t a r t of t e s t No. k 3 ; the v e r t i c a l t e m p e r a t u r e gradient i s shown i n Fig. 4. T h e r a t e of i n c r e a s e i n a i r t e m p e r a t u r e i s the g r e a t e s t a t the point of a i r injection; i t d e c r e a s e s with distance away f r o m this point a s the a i r t e m p e r a t u r e approaches the inside ambient t e m p e r a t u r e .

T e s t s Nos. A4 and A5 w e r e conducted to investigate the p e r f o r m a n c e of the s t a i r p r e s - s u r i z a t i o n s y s t e m s with other s t a i r d o o r s open i n addition to t h e one on the b a s e m e n t floor. All building air-handling s y s t e m s w e r e shut down a s i n t e s t No. A3. It w a s a s s u m e d t h a t during a f i r e the exit s t a i r door a t o r n e a r g r a d e l e v e l and the s t a i r d o o r o n the f i r e f l o o r could be expected to b e open f o r a n extended period. With t h i s in mind, t e s t No. A4 w a s conducted f i r s t l y with the s t a i r door a t the 4th floor open and secondly with the s t a i r door a t the

16th floor open, the two f l o o r s r e p r e s e n t i n g a f i r e a t low and high levels.

The p r e s s u r e differences a c r o s s the s t a i r d o o r s for both t e s t conditions a r e shown i n Fig. 5

together with those of t e s t No. A3, during which a l l s t a i r d o o r s above g r a d e w e r e c l o s e d . T h e r e w a s a s u b s t a n t i a l d e c r e a s e i n p r e s s u r e difference when the s t a i r d o o r s w e r e opened. The a v e r a g e a i r velocities through the open s t a i r d o o r s w e r e 265 f p m (5300 cfm) and 180 fpm (2600 cfm) f o r the 4th and 16th floor respectively. A minimum acceptable a i r velocity of 200 fpm i s suggested in Ref 5 to p r e v e n t smoke f r o m e n t e r i n g the s t a i r shaft.

T e s t No. A5 w a s conducted with the s t a i r d o o r s on f l o o r s 4 , 7, 8, 10, 11, 13, 14, 16, 17, 19 and 20 open to s i m u l a t e evacuation. The p r e s s u r e differences a c r o s s the s t a i r d o o r s up to the 4th floor w e r e s i m i l a r to those with only the s t a i r door on the 4th f l o o r open. Above the 4th f l o o r , however, p r e s s u r e differences w e r e considerably l e s s : v a l u e s v a r i e d f r o m 0 to 0.015 in. of w a t e r ( F i g . 5). The a v e r a g e flow velocities through t h e door opening w e r e 275, 70, 50 and 12 f p m for f l o o r s 4 , 10, 16 and 20 respectively. T h e s e values s u g g e s t that the effectiveness of the s t a i r - s h a f t p r e s s u r i z a t i o n s y s t e m with a i r injection a t the b o t t o m is not affected when s e v e r a l s t a i r d o o r s a r e opened above the f i r e floor but i s a d v e r s e l y affected when s e v e r a l s t a i r d o o r s a r e opened below the f i r e floor. A s e p a r a t e t e s t with s t a i r d o o r s of f l o o r s 3, 4 and 5 open r e s u l t e d i n a n a v e r a g e flow velocity of 120 f p m through the s t a i r door opening of the 4th floor. In a s s e s s i n g t h e s e r e s u l t s in the context of evacuation i t should be b o r n e i n mind that the p e r i o d during which e a c h s t a i r door o t h e r than the o n e s on the e x i t and f i r e flooxs i s open i s only a few minutes (the t i m e taken by the occupants t o vacate the floor).

Air Injection a t Top of S t a i r Shaft, Building B

The s c i s s o r s t a i r s of building B w e r e p r e s s u r i z e d with the two s e p a r a t e p r e s s u r i z a t i o n s y s t e m s located a t the 32nd ( m e c h a n i c a l ) floor. Although the s i z e of both fans is the s a m e , a t the t i m e of t e s t the flow c a p a c i t i e s w e r e different a s the one fan had m o r e blades t h a n the other. The outside t e m p e r a t u r e was 30 F d u r i n g the t e s t s .

T e s t No. B1 w a s conducted with the building a i r handling s y s t e m s shut down and w i t h all s t a i r d o o r s closed. Supply a i r r a t e s w e r e 16, 500 cfm and 14, 200 c f m f o r s t a i r s h a f t s NOS. 1 and 2, respectively. P r e s s u r e differences a c r o s s the s t a i r doors of s t a i r shaft No. 1 a r e shown i n Fig. 6, which shows that the p r e s s u r e differences a c r o s s the s t a i r doors a r e much g r e a t e r a t upper l e v e l s than those a t lower levels. This is a s s o c i a t e d w i t h the p r e s s u r e l o s s e s in the s t a i r shaft a l s o shown i n Fig. 6 c a u s e d by the flow r e s i s t a n c e of the s t a i r w a y

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r e s u l t i n g i n shaft p r e s s u r e s that a r e s u b s t a n t i a l l y g r e a t e r a t upper l e v e l s than t h o s e a t lower levels. P r e s s u r e differences a c r o s s s t a i r d o o r s w e r e l e s s than 0.40 in. of w a t e r except f o r t h e top two typical f l o o r s and the m e c h a n i c a l f l o o r s . The p r e s s u r e l o s s e s , and hence the v a r i a t i o n in the p r e s s u r e d i f f e r e n c e s a c r o s s t h e s t a i r d o o r s , would have b e e n g r e a t e r if the s t a i r s h a f t had b e e n the conventional type.

F r o m Fig. 7 , which shows the p r e s s u r e c h a r a c t e r i s t i c s of the floor s p a c e , s t a i r s h a f t s Nos. 1 and 2 and o u t s i d e , i t c a n be s e e n that the p r e s s u r e s of s t a i r shaft No. 1 a r e higher than those of s t a i r shaft No. 2 due t o the h i g h e r supply a i r r a t e for t h e f o r m e r . T h e n e u t r a l plane of the building w i t h the s t a i r - s h a f t p r e s s u r i z a t i o n s y s t e m s off w a s a t the 26th f l o o r level. With the s t a i r - s h a f t p r e s s u r i z a t i o n s y s t e m on, t h e f l o o r space p r e s s u r e s a l s o i n - c r e a s e d which r e s u l t e d i n the lowering of the n e u t r a l plane to t h e 16th f l o o r level ( F i g . 7). The extent of i n d i r e c t p r e s s u r i z a t i o n of the floor s p a c e s would depend upon the a i r t i g h t n e s s of the e x t e r i o r w a l l s and t h o s e of the w a l l s of t h e s t a i r shaft a s they c o m p r i s e the r e s i s t a n c e to flow i n s e r i e s f r o m the s t a i r s h a f t to the e x t e r i o r . T h e r e s u l t a n t p r e s s u r e d i f f e r e n c e s a c r o s s t h e s t a i r d o o r s would depend, t h e r e f o r e , on the a i r t i g h t n e s s of the e x t e r i o r w a l l s as w e l l a s t h a t of the w a l l s of the s t a i r shaft.

A i r t e m p e r a t u r e s of s t a i r s h a f t No. 1 w e r e m e a s u r e d one-half hour a f t e r the s t a r t of test No. B1. T h e s e a r e shown i n Fig. 8 which shows a s i m i l a r c h a r a c t e r i s t i c to those obtained f o r building A ( F i g . 4). During cold w e a t h e r , t h e p r e s s u r i z a t i o n of t h e s t a i r shaft w i t h un- t e m p e r e d outside a i r c a n r e s u l t i n uncomfortable conditions i n the s t a i r s h a f t on s e v e r a l f l o o r s extending f r o m the r e g i o n of a i r injection.

T e s t No. B2 w a s s i m i l a r t o t e s t No. B1 e x c e p t that t h e s t a i r and e n t r a n c e d o o r s on the f i r s t f l o o r w e r e open. As shown i n Fig. 6 t h e p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s w e r e l o w e r f o r t h i s s i t u a t i o n than they w e r e f o r t e s t No. B1. The a v e r a g e a i r v e l o c i t i e s through the open s t a i r d o o r s w e r e 130 and 125 f p m f o r s t a i r s h a f t s Nos. 1 and 2 respectively.

T e s t No. B 3 w a s a l s o conducted d i t h t h e s t a i r and e n t r a n c e d o o r s on t h e f i r s t f l o o r open. In addition, the s t a i r door on the 28th floor f o r s t a i r s h a f t No. 1 and s t a i r d o o r s on t h e 24th to 28th f l o o r s inclusive f o r s t a i r shaft No. 2 w e r e a l s o open. The supply a i r r a t e s i n c r e a s e d f r o m 16, 500 c f m to 19,000 c f m f o r s t a i r s h a f t No. 1 and f r o m 1 4 , 2 0 0 c f m t o 16, 200 c f m for s t a i r s h a f t No. 2. Opening of s t a i r d o o r s a t upper l e v e l s apparently r e d u c e d the s y s t e m r e s i s t a n c e which r e s u l t e d in a n i n c r e a s e i n the f a n delivery. Stack a c t i o n during cold weather c a n a l s o affect the f a n d e l i v e r y . T h e flow r a t e i s d e c r e a s e d by a f a n l o c a t e d a t t h e top and i n c r e a s e d by a fan located a t the b ~ t t o m of a building.

P r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s given in Fig. 9 a r e , below the 28th f l o o r , l e s s than 0.08 in. of w a t e r f o r both s t a i r s h a f t s . As the a i r v e l o c i t i e s a c r o s s the s t a i r door openings on the f i r s t floor w e r e low and could not be a c c u r a t e l y m e a s u r e d , the flow p a t t e r n s w e r e checked with s m o k e t r a c e s . In both s t a i r shafts a i r flowed into t h e shaft through the lower p a r t of the ~ p e n i n g and out above it. In addition, t h e s t a i r d o o r s of the 3 r d f l o o r for both s t a i r s h a f t s w e r e a l s o opened. The d i r e c t i o n of flow f o r t h e s e openings was f r o m the s t a i r shaft% to the floor s p a c e s f o r the e n t i r e opening f o r s t a i r shaft No. 1 and up to 6 in. f r o m the top of the s t a i r door f o r s t a i r shaft No. 2, above which the flow d i r e c t i o n w a s in- d e t e rminante.

The p r e s s u r e c h a r a c t e r i s t i c s f o r t e s t No. B3 a r e shown in Fig. 10. C o m p a r i s o n of this F i g u r e with Fig. 7 f o r t e s t No. B1 shows t h a t with s e v e r a l d o o r s opened the p r e s s u r e s of the s t a i r s h a f t s a r e d e c r e a s e d and t h o s e of the f l o o r s p a c e s a r e i n c r e a s e d with the n e u t r a l plane lowered f r o m the 16th to the 4 t h f l o o r level. This was c a u s e d by an i n c r e a s e i n the p r e s - s u r i z a t i o n flow and a d e c r e a s e in the r e s i s t a n c e s to flow of t h e s t a i r - s h a f t walls r e l a t i v e to those of the e x t e r i o r walls.

CONCLUSIONS

1. T h e supply a i r r a t e b a s e d on uniform p r e s s u r i z a t i o n of 0. 10 in. of w a t e r with one s t a i r door open and a l l o t h e r s c l o s e d p r o v i d e s sufficient p r e s s u r i z a t i o n t o maintain t h e s t a i r

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shaft tenable when the s t a i r d o o r s on the f i r e f l o o r and ground f l o o r a r e open. T h e s e d o o r s c a n be expected to be open f o r a n extended period d u r i n g a f i r e .

2. A s u b s t a n t i a l d e c r e a s e in s t a i r - s h a f t p r e s s u r i z a t i o n and a possibility, t h e r e f o r e , of staid- shaft contamination can be expected if s e v e r a l additional d o o r s a r e open. T h e s e d o o r s a r e likely t o be open, however, f o r a much s h o r t e r d u r a t i o n ; the t i m e f o r each d o o r i n the open position is that r e q u i r e d by the occupants to v a c a t e a floor.

3. T h e s e c o n d a r y objective of s t a i r - s h a f t p r e s s u r i z a t i o n i s to p.rovide adequate flow f o r dilution throughout the s t a i r shaft a s t h e r e i s a possibility of i t s being contaminated by smoke. A i r injection a t the bottom of t h e s t a i r shaft r e s u l t s in a s u b s t a n t i a l l o s s of supply a i r through the open e x i t door. When a i r is injected a t the top, t h e r e s u l t a n t p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s c a u s e a high r a t e of l e a k a g e flow a t u p p e r l e v e l s i n addition to c r e a t i n g p r o b l e m s w i t h o p e r a t i o n of t h e s t a i r d o o r s o n t h e s e f l o o r s .

4.

T h e b e s t a p p r o a c h would a p p e a r to be to i n j e c t a i r a t s e v e r a l levels r a t h e r than only a t the top o r bottom. In this way a s u b s t a n t i a l flow of a i r f o r dilution throughout the s t a i r shaft and a m o r e u n i f o r m p r e s s u r i z a t i o n c a n be achieved. T h e n u m b e r of outlets and locations f o r a i r injection should be such t h a t p r e s s u r e d i f f e r e n c e s a c r o s s the s t a i r d o o r s a r e between 0.10 t o 0.40 in. of w a t e r with a l l s t a i r d o o r s closed except for the one o n t h e ground floor. Relief d a m p e r s should be considered if no provision i s made f o r e n - s u r i n g continuous opening of the s t a i r door a t the ground f l o o r l e v e l d u r i n g a f i r e . F o r v e r y t a l l buildings, i t may a l s o be n e c e s s a r y to t r e a t t h e s t a i r shaft a s a number of s e g - m e n t s , i. e .

,

provide a s e p a r a t e p r e s s u r i z a t i o n s y s t e m f o r e a c h c o m p a r t m e n t .

5. T h e a i r leakage r a t e s of the s t a i r d o o r s of both t e s t buildings w e r e s i m i l a r . T h o s e of the s h a f t w a l l s of c a s t - i n - p l a c e c o n c r e t e w e r e negligible w h e r e a s those of t h e shaft w a l l s of c o n c r e t e blocks w e r e s u b s t a n t i a l . The p r e s s u r e l o s s f a c t o r s w e r e 45 and 28 f o r the conventional and s c i s s o r s t a i r s h a f t s r e s p e c t i v e l y . Such d a t a , which a t p r e s e n t a r e s p a r s e , a r e r e q u i r e d i n the design of a s t a i r - s h a f t p r e s s u r i z a t i o n s y s t e m .

ACKNOWLEDGEMENTS

The author gratefully acknowledges the contribution of the T r i z e c Equities Limited and t h e D e p a r t m e n t of P u b l i c Works f o r p e r m i s s i o n and a s s i s t a n c e i n c a r r y i n g out t e s t s in t h e i r buildings.

The author a l s o acknowledges the contributions by J. H. McGuire and C. Y. Shaw f o r t h e d i s c u s s i o n and planning of the field t e s t s and R. G. Evans f o r h i s a s s i s t a n c e i n c a r r y i n g out the field t e s t s .

T h i s p a p e r i s a contribution f r o m the Division of Building R e s e a r c h , National R e s e a r c h Council of Canada, and i s published with the approval of the D i r e c t o r of the Division.

REFERENCES

1. P. R. DeCicco, Smoke and F i r e Control i n High-Rise Office Buildings, P a r t I

-

F u l l Scale T e s t s f o r E s t a b l i s h i n g S t a n d a r d s , p r e s e n t e d a t ASHRAE Symposium on E x p e r i e n c e a n d Applications on Smoke and F i r e Control, Louisville, Kentucky, June 1973.

2. R. J. C r e s c i , Smoke and F i r e Control i n High-Rise Office Buildings, P a r t I1

-

A n a l y s i s of S t a i r P r e s s u r i z a t i o n S y s t e m s , presented a t ASHRAE Symposium on Experience and Applications on Smoke and F i r e Control, Louisville, Kentucky, June 1973.

3. R. E . B a r r e t t and D. W. Locklin, Computer Analysis of Stack Effect i n High-Rise B u i l d - i n g s , ASHRAE T r a n s a c t i o n s , Vol. 74, P a r t 11, 1968.

4.

N. A. Koplon, A P a r t i a l Report of the Henry Grady F i r e T e s t s (Atlanta, Georgia) p r e s e n - ted a t ASHRAE S y m p o s i u m on E x p e r i e n c e and Applications on Smoke and F i r e C o n t r o l , Louisville, Kentucky, June 1973.

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5. P. J. Hobson and L. J. S t e w a r t , P r e s s u r i z a t i o n of E s c a p e Routes i n Buildings, Heating and Ventilating R e s e a r c h Association, B r a c k n e l l , B e r k s h i r e , J a n u a r y 1973.

6.

G. T. T a m u r a , J. H. McGuire and A. G. Wilson, A i r Handling S y s t e m s f o r Control of Smoke Movement, ASHRAE Symposium Bulletin, F i r e H a z a r d s i n Buildings, S a n

F r a n c i s c o , Calif.

,

J a n u a r y 1970.

7. E . G. B u t c h e r , P. J. F a r d e l l and J. C l a r k e , P r e s s u r i z a t i o n a s a Means of Controlling the Movement of Smoke and Toxic G a s e s on E s c a p e R o u t e s , J F R O Symposium No. 4 , Movement of Smoke on E s c a p e Routes i n Buildings, P a p e r 5, Watford, 1969.

8. J. G. Degenkolb, Smoke P r o o f E n c l o s u r e s , ASHRAE Symposium Bulletin, Design Con- s i d e r a t i o n s f o r F i r e Safety, Philadelphia, P e n n . , J a n u a r y 1971.

9. The City of New York, Local Law No. 5, F i r e Safety R e q u i r e m e n t s and Controls, J a n u a r y 1973.

10. S t a n d a r d s Association of A u s t r a l i a , Committee ~ ~ / 4 1 Ventilation and A i r Conditioning, D r a f t A u s t r a l i a n Standard Code f o r Mechanical Ventilation and A i r Conditioning in Buildings. P a r t 2 , F i r e P r e c a u t i o n s i n Buildings with A i r Handling S y s t e m s , May 1970.

11. Uniform Building Code, Vol. 3, Housing 1970. Smokeproof E n c l o s u r e s , Chapter 33, Section 3309. I n t e r n a t i o n a l Conference of Building Officials, 50 South Los R o b l e s , P a s a d e n a , Calif.

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10,000 20,000 30,000 40,000 F L O W RATE, C F M LL

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F i g . 3 P r e s s u r e c h a r a c t e r i s t i c s w , i t h s t a i r s h a f t No. 1 p r e s s u r i z e d , t e s t No. A 3 _of_{b u i l d i n g}_A 2 2 2 0 A I R I N J E C T I O N A T F I R S T F L O O R 1 8 M E A S U R E M E N T 5 T A K E N 1 6 O N E - H A L F H O U R A F T E R V) w S T A R T O F T E S T N O . A 3 0 14 0

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1 0 I (3

-

8 O U T S I D E T E M P E R A T U R E , 5 0 ° F W I 6 4 2 B A I R T E M P E R A T U R E , OF F i g . 4 A i r t e m p e r a t u r e s o f s t a i r s h a f t No.1 o f b u i l d i n g A d u r i n g t e s t A 3

(14)

I

LEGEND - - - -

pa

o

0

Test no. A3, a l l stair doors

I

above first floor closed

a

Test no. A4, stair door on

boa

O

4th floor o w n

I

0

_{Test no.}

~ b ,

_{stair door on}

16th

floor open

ba

O

I

Test no. A5, stair doors on

I

11 floors open

too:

B U I L D I N G A I R H A N D L I N G

SYSTEMS

PRESSURE D I F F E R E N C E A C R O S S S T A I R D O O R S , I N C H O F WATER F i g . 5 P r e s s u r e d i f f e r e n c e s a c r o s s s t a i r d o o r s f o r t e s t N o . A 4 a n d t e s t N o . A 5 o f b u i l d i n g A ( o p e n d o o r t e s t s ) AIR I N J E C T I O N AT 3 2 N D FLOOR

\

LEGEND

0 _Testno. B1, supply air rate

\

16,500ch all stair doon

closed

\

Test no. B2, sqply air rate 16,000 c h stair door and

\

entrance door on first floor \ opsn

I

OUTSIDE TEMPERATURE,

\

35.F PRESSURE LOSSES I N

\

STAIR SHAFT N O . 1 F i g . 6 P r e s s u r e d i f f e r e n c e s a c r o s s s t a i r d o o r s o f s t a i r s h a f t N O 1 t e s t N o . B 1 a n d t e s t N O . B 2 o f b u i l d i n g B 1B 3 8 5B - 0 . 2 0 0 0.20 0.40 0 . 6 0 0 . 8 0 1 .OO 1 .20 PRESSURE DIFFERENCE ACROSS STAIR DOORS,

I N C H O F WATER

-

4

I

0 0 K>

I

i

(15)

=

Z UJ UJ + Y L L Y 0 0 6

--

I-= rn v 2 ; m z c

+o;

9 0

Z l +

₂

+:,

3

u

Y

z 5 u

I- 6

-

rir I-

"u

2 4 0

h

o z

zCVg

? ? I - W

- -

W v , w = u-l

=

-'-.a

-

$ 2 2

2 2 s

-

< a -

zom

I- O u

1 1 1

I

I .

I

I I

I

I I

I

i

I 1 1 1 1

z

m m a - 0 _u + J v l '44 0 m u .c: rn bl c - 0 k ..r h .-I rc m a O u a rn p 9 w '44 - O

=

obl

2

a,.: k a

2

3 - y U '1 n m a

- o , r

t 4

w 444 + 5 0 0 Y U Y Q

-

6 k . .

*

'1 0 0 - 2 2 m m 0 '-I bl k4 0 CV cv O O D ~ P O O D ~ P C V O O D cv - m~ Pv , 0 O ( V C V N C V C V - a - - - -S I O O l J ' l H 9 1 3 H

(16)

) 0 A I R I N J E C T I O N A T 3 2 N D F L O O R B 0

LEGEND

Stuir shaft no. 1, supply air rate 19,000 cfm stair doors on floor 1 and 28 open Stuir shaft no. 2, supply air rate 16,200 cfrn stair door on floors 1, 24, 25, 26, 27, 28 open - 0 . 2 0 0 0 . 2 0 0 . 4 0 0 . 6 0 0 . 8 0 1 . O O PRESSURE D I F F E R E N C E A C R O S S S T A I R D O O R S , I N C H O F WATER F i g . 9 P r e s s u r e d i f f e r e n c e s a c r o s s s t a i r d o o r s f o r t e s t N O . B 3 o f b u i l d i n g B ( o p e n d o o r t e s t s ) STAIR SHAFT STAIR SHAFT AIR I N J E C T I O N AT 3 2 N D F L O O R B U I L D I N G AIR LEGEND H A N D L I N G _{SYSTEMS S H U T D O W N} OStair h a f t no. 1, 19,000 cfm

doon open on floon 1 and 28 *Stair h a f t no. 2, 16,200 cfm

doon open on floors 1, 24, 25, O U T S I D E TEMPERATURE, 26,

n,

28

0 Floor space

NEUTRAL P L A N E

PRESSURE DIFFERENCE SCALE

I +

0 0 . 2 0 0 . 4 0 0 . 6 0 AP, I N C H O F WATER

v

ABSOLUTE PRESSURE ---e-

F i g . 1 0 P r e s s u r e c h a r a c t e r i s t i c s w i t h

s t a i r s h a f t s p r e s s u r i z e d a n d

s e v e r a l s t a i r d o o r s o p e n , t e s t

(17)

MR. J . C . OLSEN (Tamblyn M i t c h e l l & P a r t n e r s , T o r o n t o , O n t a r i o , Canada): The s l i d e s i n d i c a t e d t h a t t h e t e s t was conducted i n summer. Were any of t h e t e s t s conducted a t c o l d t e m p e r a t u r e s ? I f s o what was t h e e f f e c t on s t a i r p r e s s u r i z a - t i o n w i t h c o l d o u t s i d e a i r 3 Do you a n t i c i p a t e a r e q u i r e m e n t t o h e a t t h e a i r ?

MR. TAMURA: O u t s i d e t e m p e r a t u r e s d u r i n g s t a i r p r e s s u r i z a t i o n t e s t s were 50F w i t h a i r i n j e c t i o n a t t h e bottom and 35F w i t h a i r i n j e c t i o n a t t h e t o p . Measurements of a i r t e m p e r a t u r e i n s i d e t h e s t a i r s h a f t i n d i c a t e d t h a t t h e s e t e m p e r a t u r e s

w e r e

c l o s e t o t h a t o u t s i d e n e a r t h e p o i n t of a i r i n j e c t i o n b u t i n c r e a s e d r a p i d l y away from it u n t i l a t a d i s t a n c e of a b o u t t e n f l o o r s away, t h e y approached t h e i n s i d e ambient a i r t e m p e r a t u r e a s i n d i c a t e d i n F i g . 4 and F i g . 8 .

I n j e c t i o n of unheated o u t s i d e a i r i n t o t h e s t a i r s h a f t d u r i n g c o l d weather does n o t a d v e r s e l y a f f e c t t h e performance of a s t a i r p r e s s u r i z a t i o n system. The r e q u i r e m e n t t o h e a t t h e s u p p l y a i r , t h e r e f o r e , depends on whether o r t o what d e g r e e c o m f o r t c o n d i t i o n should he provided f o r o c c u p a n t s e v a c u a t i n g t h r o u g h t h e s t a i r s h a f t .

(18)

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