ous materials in circulation corridors, requiring noncirculation corridors for such use. Corridor and door widths and elevator cab sizes and capacities should all be considered with these special needs in mind during the design process.

Access

Points of access to research laboratories, teaching laboratories, and laboratory support areas have to accommodate people and also large, bulky, and potentially hazardous materials. Large items require wide corridors, wide doors, large elevators, and specially designed corners to permit a wide turning radius. Transporting extremely heavy items within a building may be restricted or even prohibited if the building was not designed to support extremely heavy loads. If only part of the building is designed to support extremely heavy loads, the circulation corridors and elevators used to access that pan of the building must also be designed to support the heavy loads.

A 36-inch-wide door is standard for laboratories and laboratory support areas; however, commonly used laboratory equipment and large instruments may require a wider door opening. Door widths of 42 or 48 inches should be considered in these instances. If a single door leaf of 42 or 48 inches is heavy, it may require special hardware to meet ADA access requirements. Double doors could also be used, but a common solution is to use two doors of unequal width. Typically a 36-inch door, called the active leaf, is used with an 18- to 24-inch door called the inactive leaf. The 36-inch door, the minimum size required to comply with ADA requirements, is used on a daily basis to access the laboratory. The smaller door can be opened easily in the infrequent instances when the extra width is needed to move a large item into or out of the laboratory.

For similar reasons, corridors 6 feet wide or wider are common in research laboratory facilities. Narrower corridors do not permit the movement of large items and can obstruct the bidirectional flow of traffic. Even corridors 6 feet wide may not provide a turning radius sufficient for some large items to turn a comer through a door along the corridor.

Elevators pose similar problems. The width and height of the elevator doors, the size of the cab, and the capacity of the elevator all are critical to the efficient movement of large and heavy items throughout the building. Where large pieces of equipment must be moved, high ceilings and doorways are required. Corridors often must have ceiling heights greater than 8 feet. The movement of tall apparatus may require doorways taller than 7 feet. These standards, regularly used for other building types, should be reexamined when planning a research laboratory facility. Corridor ceiling heights of 9 or 10 feet and door heights of 8 or 9 feet may be required in parts of a building where large equipment is used and moved.

The entry to the building and the pathways within the building for movement of large equipment start at the loading dock and must be clear of any low obstructions. During the lifetime of a building, large pieces of equipment will



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