What Does
Warning Line System Mean?
A warning line system is a safety measure used to prevent falls on construction sites. It consists of a line (made of rope, chain, or chain) held up by stanchions with flags attached at regular intervals.
Unlike guardrails, warning lines do not stop someone from falling. Rather, they are a visual reminder of fall hazards and demarcate the area where there is a higher risk of falling.
It also marks off the area where work can be done without fall protection equipment like safety nets and safety belts.
Safeopedia Explains Warning Line System
The Occupational Safety and Health Administration (OSHA) allows warning line systems to be used only on low-slope roofs. Warning lines must be set up at least six feet from the unprotected edge, and used in conjunction with other fall protection systems, such as:
What a Warning Line System Consists Of
A warning line system is made of three components (the line, stanchions, and flags) and may include an access point.
Supporting Stanchions
The stanchions are standing posts with a wide base for stability. The line is attached to these posts, creating a fence.
OSHA 1926.502(f)(2)(iii) requires that warning line stanchions be capable of resisting a minimum force of 71 Newton (16 pounds) applied horizontally at 30 inches above the walking-working surface.
Line
The line can be made of wire, rope, or chain. OSHA 1926.502(f)(2)(ii) and (v) specifies that, after rigging and supporting the line on the stanchions, the lowest point of the line must be at least 34 inches from the walking-working surface, with the highest point no more than 39 inches from that surface.
When a section of the line between stanchions is pulled, it should not cause slack in adjacent sections.
High-Visibility Flags
Flags must be affixed to the line, at a maximum interval of six feet.
These flags act as visual reminders of the fall hazard nearby. As such, they must be made of high-visibility materials.
Access and Egress
If a point of access is needed, a path can be created with two warning lines connecting to the work area.
When the path is not in use, the access point must be blocked by a line or barrier.
OSHA’s Warning Line System Requirements
According to OSHA 1926.502(f), the warning line must be set up on all sides of the roofing work area, at a minimum distance of six feet from the edge. While this is a minimum, a setback of 10 feet from the unprotected edge is preferable.
If mechanical systems are being used in the work area, the warning line must be erected at least 6 feet from the roof edge parallel to the direction of the operation of the equipment, and at least 10 feet from the edge perpendicular to the direction of its operation.
Where necessary, the distance can be further increased to eliminate the fall risk. For instance, poor visibility, inclement weather, the type of work being performed, or slippery surfaces can all be reasons to set up the warning line further away from the edge.
The warning line must be strong enough to resist the horizontal force exerted by a worker tripping and falling onto the line or one of its stanchions. As per OSHA 1926.502(f)(2)(iv), the line must have a minimum tensile strength of 500 lbs (2.22 kN).
Requirements for Non-Roofing Activities
For non-roofing work taking place on a roof, warning lines must meet the following conditions:
- The line is set up at least 15 feet from the unprotected edge
- The line meets OSHA requirements for warning line systems
- The roof has a low slope
- There is no work taking place outside the warning line’s perimeter
- The workplace has an effective policy prohibiting workers from breaching the warning line
Conventional Fall Protection and Safety Monitor
Warning lines are beneficial on low-slope roofs because conventional means of fall protection like PFAS, guardrails, and safety nets are not required if a safety monitor is in place. A safety monitor is a competent person who can recognize fall hazards and ensure that workers are being safe around them. The main job of a safety monitor is to look out for workers and ensure no one is near a fall hazard.
A safety monitor must:
- Be on the same surface as the employees
- Be able to observe all the employees from their vantage point
- Be close enough to be seen and heard by all the employees
- Warn the employees when they are near a fall hazard or otherwise behaving in a way that puts the at greater risk of falling
Inspection and Maintenance Requirements
Warning lines must be well-maintained and inspected regularly to ensure their effectiveness. A damage warning line may not be able to withstand the force needed. Lines may eventually start to sag below the acceptable level. Warning lines are also sometimes moved around and may no longer have the required minimum distance from the edge.
Warning line systems must be inspected by a qualified safety inspector to verify that it is in good condition and installed in compliance with OSHA regulations. If a warning line fails to meet the requirements, it needs to be adjusted accordingly, or replaced if it cannot be adjusted. The high-visibility flags must be replaced when their coloring fades.
Limitations of Warning Lines in Fall Protection
A warning line system is a visual reminder of the proximity of a fall hazard. It’s an effective tool when used in conjunction with other fall protection measures. However, it does have inherent limitations that must be taken into consideration:
- Since the stanchions are not fixed in place, they can be moved, which could result in the warning line system being positioned too close to the edge
- A warning line system relies on worker compliance – it is only effective if everyone on the site remains within its boundaries
- Since work within the designated area can be performed without additional fall protection systems, workers who go outside the boundaries of the demarcated area will be unprotected
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