8. In buildings with relatively modest requirements for mechanical services, horizontal distribution may take place primarily above a central corridor or above a strip of dropped ceiling that runs around the perimeter ol'"the building. This is an economical approach :hat can work well in hotels, dormitories, apartment buildings, and classroom buildings.

In general, any horizontal plenum space must connect generously with the vertical passages that feed it. Where i: meets a lire wall or a lire separation vail, the wall must penetrate up through ihe plenum to close tightly against the structural floor above. Anv ducts that cross this fire separation must be provided with lire dampers, and any other penetrations must be sealed with lire-rated construction. Care should be taken to avoid acoustical flanking paths through a plenum space (page 70).

one hundred five


MILLIONS of people arc injured needlessly each year in unsafe buildings, and millions more become ill because of unhealthy buildings. People trip and fall on unsafe floors and stairs. They cut, scrape, and gouge themselves on rough surfaces, sharp edges, and broken glass. They are poisoned by fumes from various adhesives and plastics, and by smoke from building fires. People who are ill, aged, or otherwise disabled may find themselves unable to reach whole areas of a building because of physical barriers that have been incorporated into the architecture. Most health and safety issues in detailing are regulated by building codes; others arc merely based on common sense.

Detail patterns relating to health and safety are the following:

Safe Footing (page 106) Fall Protection (page 107) Safe Edges (page 109) Safe Glazing (page 110) Nontoxic Materials (page 111 ) Firesafe Materials (page 112) Fire-Resistant Assemblies (page 113) Barrier-Free Design (page 114)

Tripping and slipping arc two occurrences that the detailer must guard against in floor and stair details.

1. Tripping on floors can be caused by floor-mounted doorstops, unusually high thresholds, and abrupt changes in floor level or floor material.

2. Tripping on stairs can be avoided by careful compliance with building code provisions. Proportion treads and risers as the code requires, and take care when inspecting construction that excessive variations do not creep into tread and riser dimensions. Do not design stairs that have only one or two risers; people tend not to see them until they have fallen on them.

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