U.S. Department of Labor
Occupational Safety & Health Administration
Covers. The employer must ensure each cover for a hole in a walking-working surface:
Is capable of supporting without failure, at least twice the maximum intended load that may be imposed on the cover at any one time; and
Is secured to prevent accidental displacement.
Part Number: 1926
"Covers." Covers for holes in floors, roofs, and other walking/working surfaces shall meet the following requirements:
Covers located in roadways and vehicular aisles shall be capable of supporting, without failure, at least twice the maximum axle load of the largest vehicle expected to cross over the cover.
All other covers shall be capable of supporting, without failure, at least twice the weight of employees, equipment, and materials that may be imposed on the cover at any one time.
All covers shall be secured when installed so as to prevent accidental displacement by the wind, equipment, or employees.
All covers shall be color coded or they shall be marked with the word "HOLE" or "COVER" to provide warning of the hazard.
Note: This provision does not apply to cast iron manhole covers or steel grates used on streets or roadways.