Buy CEN/TR SMOKE AND HEAT CONTROL SYSTEMS – PART 5 : GUIDELINES ON FUNCTIONAL RECOMMENDATIONS AND CALCULATION. exhaust ventilation systems (published as CR ). Part 6: Specification for pressure differential systems — Kits. Part 7: Smoke control. Design approaches for smoke control. in atrium buildings. G 0 Hansell*, BSc, PhD, CEng, MCIBSE, AlFireE H P Morgan, BSc, CPhys, MlnstP, AlFireE.
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The concept of this space has evolved architecturally over the past few hundred years and now applies to structures much larger than the typical Roman house. The atrium space generally has no functional use other than as a circulation area Figure 1. These flow outwards below the ceiling until they reach a barrier eg the walls, or a downstand.
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The pressure drop criterion may be increased if the population of the building is adult and physically fit, to perhaps Pa 8 ms-I. Where the boundary between the room and the atrium is open, it is sometimes feasible to provide a smoke ventilation system within the room, to maintain smoky fire gases above the opening to the 21101-5. Table 4 strictly applies to ventilators which are small compared to the layer depth below the ventilators eg where the diameter is much less than the depth of the layer.
Experience of pressurisation designs suggests that the technique is well-suited to the protection of K I Heat radiation Figure 6 T h c onset of flashover 5 stairways used as escape routes in tall 121001-5, though it can also be useful in other circumstances.
Note that depressurisation does not protect the smoke-affected space in any way; instead it protects the adjacent spaces.
BS en 12101-5
There have been a number of purely qualitative papers, as well as papers on work using relatively simple models of smoke movement within atria see for example References Instead it gives general principles for the design of efficient systems, with simplified design procedures for an ideal model of an atrium, and then further guidance on frequently encountered practical problems.
Being close, smoke issuing from such a compartment will deepen locally on meeting a transverse barrier.
The depth of the established layer DB in Figure 21 under the balcony immediately downstream of the local deepening must first be found using the design procedure given in the preceding sections. This accords to a face velocity across a rectangular sn opening of about 6 ms-I. This Report is the culmination of a long-running collaborative project between the Fire Research Station of the Building Research Establishment and Colt International Limited on aspects of smoke movement and its control in atrium buildings.
In either case, the threat to means of escape which are either within the atrium or in spaces open 1.
There is no information available to show how Equation 1 or any current alternatives should be modified to 1210-5 for the effects of sprinkler spray interactions. Sprinklers may also be required in other circumstances for insurance purposes.
As the fire grows and declines, the mismatch in volume between the inlet air and the extracted fire-warmed air will also change. The pressure difference enn any small opening on to the route must be large enough to offset adverse pressures caused by wind, building stack effect and fire buoyancy. The extent of local deepening can be found from Figure Screens may be fixed or may descend upon smoke detection.
If the compartment is open to the atrium, then the gases flow out immediately they reach the opening. When ventilating compartments directly, if the faiade is normally sealed then facilities should be provided for the necessary quantity of replacement air to be supplied to the fire room automatically.
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The Report cannot cover all the infinite variations of atrium design. Even if there is a very large ventilation area downstream eg if the ceiling downstream were to be removedthis flowing layer would still have a depth related to the width available under the remaining ceiling which can now be considered a balconythe temperature of the smoke and the mass flow rate of smoke.
The populations within such buildings are also greater; hence there has been a substantial increase in the number of people to be protected and evacuated in an emergency. This effect can be expressed as a modification to the coefficient of discharge as follows: Recent work by Hanseldrawing on work by Zukowski et aand Quintiere et ahas shown that the rate of air entrainment into a plume of smoke rising above a fire Mmay be obtained by using the equation: Other values may be appropriate for other circumstances.
Multi-storey buildings in the assembly, shop, industrial or storage purpose groups will also be fitted with sprinklers if individual uncompartmented floors exceed a given size. Note however, that pressurising the atrium may be a viable option where the atrium faqade has only relatively small leakage paths.
I Figure 20 Under-balcony smoke reservoir venting into an atrium smoke reservoir Entrainment into smoke flows from compartments is being studied When the fire occurs in an office, the operation of sprinklers under the balcony will not assist in controlling it.
Larger chambers should be subdivided by smoke screens extending the full height of the chamber dn below the false ceiling to form a complete smoke reservoir below. In most practical compartments there is sufficient oxygen to support combustion in the first few minutes, and the fire growth and smoke production are controlled by the fuel, ie, fuel-bed control.