Malls, sprinklers and smoke: is smoke in a shopping mall atrium more of aproblem than we bargained for? Recent tests have been looking at the concerns

In North America, it has generally been assumed that communicating spaces connected to an atrium or mall will be sprinklered and, as a result, the sprinklers will limit the size of a fire in the adjoining space. As a result, engineering design guides for smoke management systems such as National Fire Protection Association NFPA 92B(1) have assumed that the smoke will have minimal effect in the atrium or mall space. The design guides, however, do allow for smoke management designs in which the smoke is allowed to spill into the atrium space. During the steady fire phase, hot smoke continued to flow into the mall area and a smoke layer formed there even though the smoke exhaust system was in use. Hot smoke flowed into the mall area for up to 20 minutes depending on the test conditions. The optical density of the smoke in the upper portion of the simulated mall and its carbon monoxide concentration both exceeded tenability limits. Any accumulation of this smoke in exit routes could limit evacuation. In addressing concerns that smoke cooled by sprinklers in retail spaces connected to malls could travel down and endanger people evacuating the building, the results of the study indicate that during the initial stages -- fire growth and steady fire phases -- the smoke entering the mall area is hot and rises towards the ceiling. A smoke management system using mechanical exhaust could be used to remove this smoke.