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The width of aisles and passageways is generally not specified in OSHA standards, other than in specific instances. Examples of these specific instances include requirements for aisles 3 feet wide in inside storage rooms holding flammable and combustible liquids (1910.106) and requirements for minimum exit access widths of 28 inches (1910.36(g)(2)-(3)). And while 1910.176(a) outlines general aisle requirements, it does not specify aisle widths.
However, a May 15, 1972, OSHA Letter of Interpretation (since withdrawn) said, “The recommended width of [permanent] aisles is at least 3 feet wider than the largest equipment to be utilized, or a minimum of 4 feet.” The width of the largest equipment includes the width of the widest carried if the load is wider than the frame of the equipment. For example, forklifts might carry 12 foot long lumber horizontally on the forks, so the aisle width must be 15 feet.
Employers must also comply with any applicable local or state building and fire codes.