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Research I NationalCanada Council 1618

Conseil national de recherches Canada

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Institute for Research in Construction

lnstitut de recherche en construction

Stair Pressurization Systems for Smoke Control: Design Considerations
by G.T. Tamura

Reprinted from ASHRAE Transactions, 1989 Vol. 95, Pt. 2, 9p. (IRC Paper No. 1618)

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NRCC 30896

On a fait m e 6tude de synthbse sub les divers types de systi5mes de mise en pression, l'utilisation des escaliers lors de 1'Cvacuation et les exigences des codes. Des essais sans feu et de tenue au feu ont C effectu6s dans la tow d'incendie de 18 Ctages du Labomtoire t C national de'19incendie,au Conseil national derecherches du Canada. On a mesun5 la C dsistzaflce B l'koulement de 19air u e p a d'escalier ouverbe B divers angles. h s profils verticaux des Ccarts de pression de part et d9autredu mur de la cage d'escalier et ceux de la pression de vitesse dans l'ouverture de la p r t e d'escalier ont BtC mesuds dans des conditions d'incendie. La cage d'escalier Btant en pression, les vitesses critiquesnkcessaires pour empecher le refoulement de la fumBe dans l'ouverture de la porte d'escalier, h 196tage l'incendie, ont 6tC d6termin6es et compdes aux valeurs calcul6es de pour diverses temp6rature de feu.

Stair Pressurization Systems for Smoke Control: Design Considerations
G.T. Tamura, P.E.
Fellow ASHRAE

ABSTRACT Literature on the various types of pressurization systems, stair use duringevacuation, and code requirements was reviewed and summarized. Non-fire and fire , tests were conducted in the 70-story experimental fire tower of the National Fire Laboratory of the National Research Council of Canada. The flow resistances of an open stair door at various angles were measured. Under fire conditions, the vertical profiles of pressure differences across the stairshaft wall and thoseof the velocity pressure at the stair door opening were measured. With the stairshaft pressurized, the critical vqlocities required to prevent smoke backflow at the stair door opening on the fire floor were determined and compared with the calculated values for various fire temperatures. INTRODUCTION Various methodsfor protecting stairwellsfrom smoke intrusion during a fire have evolved over thepast several years. The one used most often in North America is the stairshaft pressurizationsystem. Designing such systems is complicated because an intermittent loss of effective pressurizationoccurs when occupants enter and leavethe stairs during evacuation. Therefore, the pressurization system should have a supply air fan with sufficient capacity to provide effective pressurizationto preventsmoke entry when doors are open and a means of preventing overpressurization, which can make door opening difficult when all doors are closed. To prevent such overpressures, the design concepts of barometric damper relief,feedback control with fan bypass, variable-speedor variable-pitch fan, and exit door relief have been developed. Although many such systems have been built, it is not known atpresent to what extent they are effective. An ASHRAE research project, RP-559, was undertaken with the objective of assessing these systems and developing design recommendationsfor various methods of overpressure relief. It involves (1) a literature review, (2) field tests, (3) full-scalefire tests, and (4) a design analysis. In this paper the results of studies conducted during the first phase of theproject are presented.They involved a literature review of stair pressurizationsystems, stair use during evacuation, and code requirements.They also involved tests in the experimental fire tower to determine flow

coefficients for various angles of door opening, with and without people, and critical air velocities to prevent smoke backflow at an open stair door for various fire temperatures....