Warning Lines & Safety Monitoring Systems
Warning lines and safety monitors are fall protection options OSHA allows only in limited situations, mainly roofing work on low-slope roofs. They don’t physically stop a fall, so the rules for using them are strict.
- Construction
- Roofing
When they’re allowed (construction)
- Roofing work on low-slope roofs (4 in 12 or less) with unprotected edges 6 feet or more above a lower level: a warning line combined with guardrails, safety nets, personal fall arrest or a safety monitor.
- Safety monitoring alone is allowed for roofing work on low-slope roofs 50 feet wide or less.
- Under a written fall protection plan for leading edge, precast and residential work when conventional protection is infeasible. See Fall Protection Plans.
Warning lines don’t replace fall protection for workers who go between the line and the edge.
Warning line requirements (summary)
- Set at least 6 feet back from the roof edge on all sides
- Near mechanical equipment: at least 6 feet back parallel to the direction of travel and 10 feet perpendicular to it
- Rope, wire or chain flagged with high-visibility material at least every 6 feet
- Line 34 to 39 inches high at its lowest point
- Stanchions that won’t tip over when pushed with 16 pounds of force near the top
- Access paths into the work area marked with a line or barricade
Safety monitor duties
- Be a competent person who can recognize fall hazards.
- Be on the same walking surface and within sight of the workers.
- Be close enough to warn workers by voice.
- Have no other duties that take attention away from monitoring.
- Warn workers right away when they’re unaware of a fall hazard or acting unsafely.
Mechanical equipment (like roofing machines) isn’t allowed in areas protected only by a safety monitor.
Monitors and lines don’t catch anyone. They depend on attention, and attention fails. Guardrails, nets and personal fall arrest are more reliable, and general industry rules are stricter about when lines can be used. See Guardrails.
General industry
Under the 2016 walking-working surfaces rule, general industry uses “designated areas” with warning lines on low-slope roofs only for temporary, infrequent work set back far enough from the edge (generally at least 6 feet, and 15 feet or more in some cases). See Walking-Working Surfaces.
Standards & references
- 29 CFR 1926.502(f) and (h): Warning lines and safety monitoring
- 29 CFR 1926.501(b)(10): Roofing work on low-slope roofs
- See also: Roof Work
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