Fall distance and safety factor for horizontal lifelines

February 9, 1995
Mr. J. Thomas Wolner
D.B. Industries, Inc.
[Recipient address omitted]
Dear Mr. Wolner:
Your December 5 letter addressed to Ms. Barbara Bielaski requesting an interpretation of the Occupational Safety and Health Administration's (OSHA) final rule on fall protection concerning the criteria for personal fall arrest systems has been forwarded to the Office of Construction and Maritime Compliance Assistance for response.
Your interpretation regarding total fall distance experienced by the user during fall arrest on a horizontal lifeline is correct as stated in your letter. Specifically, the free fall distance is limited to 6 feet; the deceleration distance must not exceed 42 inches; lifeline elongation is not included in deceleration distance; and the total fall distance is unregulated except that the employee cannot make contact with a lower level.
Regarding your question on applying the safety factor, the safety factor of two should be applied based on the anticipated maximum arrest force and not the fall energy. The example in your letter of determining the maximum arresting force and then doubling that figure to arrive at the system design load is the approach to be taken.
If we can be of any further assistance, please contact me or Mr. Dale Cavanaugh of my staff at (202) 219-8136.
Sincerely,
Roy F. Gurnham, P.E., J.D. Director
Office of Construction and Maritime Compliance Assistance

[Requester letter reproduced on OSHA page; omitted here.]