Chapter 1 Smoke control overview
Note:
Atrium smoke control should not activate on signals from sprinkler water flow switches or heat detectors. Since the temperature of a smoke plume decreases with height, activation by these devices may not provide reliable results.
Beam smoke detectors minimize interference problems created by stratified hot air under atrium ceilings. On hot days or days with a high solar load on the atrium roof, a hot layer of air may form under the ceiling. The layer can exceed 120° F (50° C). The smoke from an atrium fire may not be hot enough to penetrate the layer and reach ceiling- mounted smoke detectors (Figure 9).
Figure 9: Sample stratification
Vertical grid
The vertical grid is the most common beam detector configuration. A number of beam detectors, located at different levels under the ceiling, detect the formation and thickening of a smoke layer. The bottom of the grid is at the lowest expected smoke stratification level.
Horizontal grid
The horizontal grid is an alternate beam detector configuration A number of beam detectors, located at different levels under the ceiling, detect the rising smoke plume. Beam detectors are located:
•Below the lowest expected smoke stratification level
•Close enough to each other to ensure intersection with the plume
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