Does OSHA specify a minimum aisle width?

OSHA doesn’t actually have a minimum width for pedestrian aisles, unless the aisle is part of an emergency egress route. The egress route regulation at 1910.36(g)(2) requires a minimum of 28 inches. In addition, paragraph (g)(3) says that the width must be sufficient to accommodate the maximum occupant load, so egress route aisles may need to be wider than 28 inches depending on the number of people who will use them to evacuate.

Also, OSHA adopted the minimum of 28 inches many years ago and it applied to existing structures. For newer construction, guidance from the National Fire Protection Association or local fire codes might require an aisle wider than 28 inches. For example, Michigan OSHA specifies a minimum of 34 inches for exit access.

Beyond exit routes, OSHA doesn’t specify a minimum width for aisles. Our experts commonly get questions about a 4-foot minimum width in warehouses, but that’s not a regulatory requirement. OSHA mentioned that distance in an old OSHA letter of interpretation from 1972 that has since been withdrawn. The archived letter stated, “The recommended width of aisles is at least 3 feet wider than the largest equipment to be utilized, or a minimum of 4 feet.”

Since that letter was “active” for about 30 years, a lot of employers ask about the 4-foot requirement. However, that “recommended width” is not enforceable, and as noted, the letter has been withdrawn. There’s no OSHA requirement for pedestrian aisles to be four feet wide.

Egress routes must be clear and unobstructed at all times. Blocking an exit route is a common violation in warehousing, retail, and manufacturing. The egress regulation at 1910.37 requires that exit routes remain clear at all times; those routes cannot be obstructed even for short periods.

Stairs and catwalks

Warehouse and office aisles aren’t the only potential egress routes. In a multi-story structure, workers likely use stairs to evacuate upper levels. Although OSHA’s regulation on stairways at 1910.25(c)(4) requires a minimum width of only 22 inches, any stairway that is part of an egress route must be wider.

Also, catwalks or runways could technically be as narrow as 18 inches according to 1910.28(b)(5)(ii)(A). If the runway is part of an egress route, however, it must be wider.

Mechanical equipment

Another reference to aisles appears in 1910.176 which requires “sufficient safe clearance” where forklifts or other mechanical equipment is used. Although OSHA withdrew the previously-mentioned interpretation, ensuring that aisles are at least 3 feet wider than the equipment is still a good practice to ensure sufficient clearance.

In addition, 1910.176(a) requires that aisles be kept clear, with no obstructions that could create a hazard. OSHA doesn’t cite this paragraph nearly as often as the one for obstructing exit routes, but does issue a few dozen per year. For example, the U.S. Postal Service received a citation under 1910.176(a) for allowing wheeled mail carts in marked forklift aisles, which OSHA said created struck-by and caught-between hazards.

In addition to ensuring “adequate” or “safe” width, aisles must be clear and unobstructed at all times. Employers must keep egress routes clear, but blocking designated forklift aisles could result in citations as well.