2.2 Nets, warning lines, access zones and safety monitors

1 Safety nets: passive, and mostly for bridges

Safety net systems are named in most of 1926.501(b) and used almost nowhere in building construction, because they are expensive to rig, need clearance below, and require drop testing. Where they earn their place — bridge work, long-span steel, and over occupied space — they are the only system that catches a worker who never wore anything.

The criteria are in 1926.502(c):

The horizontal projection in (c)(2) is the part that surprises people. A net that only reaches 4 feet out from a bridge deck does not catch a falling worker; it catches them after they have passed it. The projection grows with the fall distance for exactly that reason.

2 Warning line systems: roofing only

A warning line is a rope, wire or chain on stanchions that marks a zone near a roof edge and keeps everyone out of it. It is not a barrier and it will not stop anybody; it works by making the edge unmistakable. Under 1926.501(b)(10) it is available only for roofing work on a low-slope roof, and — with one exception noted below — only in combination with a guardrail, safety net, personal fall arrest, or a safety monitoring system.

The criteria are in 1926.502(f):

• Erected around all sides of the roof work area — (f)(1).
• Not less than 6 feet from the roof edge when no mechanical equipment is in use — (f)(1)(i).
• With mechanical equipment: not less than 6 feet from the edge parallel to the direction of operation, and not less than 10 feet perpendicular to it — (f)(1)(ii) and (iii).
• Flagged at not more than 6-foot intervals with high-visibility material — (f)(2)(i).
• Rigged and supported so the lowest point including sag is no less than 34 inches and the highest point no more than 39 inches above the walking/working surface — (f)(2)(ii).
• Stanchions capable of resisting, without tipping over, a force of at least 16 pounds applied horizontally against the stanchion 30 inches above the surface, in the direction of the roof edge — (f)(2)(iii).
• Rope, wire or chain with a minimum tensile strength of 500 pounds, attached so that pulling on one section does not slack adjacent sections — (f)(2)(iv) and (v).
• Access paths bounded by two warning lines, and closed off with a rope, wire, chain or other barricade when not in use — (f)(3).
• No employee is allowed between the roof edge and a warning line unless performing roofing work in that area — (f)(4).

The one exception: under 1926.501(b)(10), on a roof 50 feet or less in width, a safety monitoring system may be used alone, without a warning line. That is the narrowest option in the whole standard and the most abused.

3 Controlled access zones

A controlled access zone, or CAZ, is an area where certain work may take place without guardrails, nets or fall arrest, and into which access is limited to authorized employees. It appears in three places: leading edge work and precast erection under a 1926.502(k) fall protection plan, and overhand bricklaying under 1926.501(b)(9)(i).

1926.502(g) sets the control line geometry:

The line itself: ropes, wires, tapes or equivalent materials on supporting stanchions, flagged at not more than 6-foot intervals with high-visibility material, with the lowest point including sag not less than 39 inches and the highest point not more than 45 inches — 50 inches for overhand bricklaying — and a minimum breaking strength of 200 pounds. The line must extend along the entire length of the unprotected or leading edge and be approximately parallel to it, connected on each side to a guardrail system or wall.

And the rule that gives it meaning: in a CAZ for overhand bricklaying, only employees engaged in overhand bricklaying or related work may enter; in a CAZ for leading edge or precast work under a fall protection plan, only employees authorized by the employer and named in the plan may enter.

4 Safety monitoring: one job, and only one job

Safety monitoring is a person. 1926.502(h)(1) requires the employer to designate a competent person to monitor the safety of other employees, and that person must:

1. 1
   Be competent to recognize fall hazards.
2. 2
   Warn the employee when it appears the employee is unaware of a fall hazard or is acting in an unsafe manner.
3. 3
   Be on the same walking/working surface and within visual sighting distance of the employee being monitored.
4. 4
   Be close enough for oral communication.
5. 5
   Have no other responsibilities which could take the monitor's attention from the monitoring function.

Then the conditions on the arrangement itself, in (h)(2) through (h)(5): mechanical equipment shall not be used or stored in areas where safety monitoring systems are being used; no employee other than one engaged in roofing work — or covered by a fall protection plan — may be in an area where an employee is being protected by a safety monitoring system; and each employee working in a controlled access zone shall be directed to comply promptly with fall hazard warnings from the monitor.

Put those together and the option collapses in most real roofing operations. A kettle, a power buggy, a hoist, a saw on the deck — any of them ends it. A foreman who is also laying out, ordering material and answering the phone is not a monitor. And if a second trade steps onto that roof, the arrangement is void.

5 Choosing between them

Ranked by how much they depend on human behavior, from least to most: guardrails and covers (no behavior), safety nets (no behavior at the moment of the fall, but weekly inspection and drop testing), personal fall arrest (correct connection, correct anchor, adequate clearance), warning lines (staying out of the zone), controlled access zones (staying out, plus authorization), safety monitoring (one person's continuous attention protecting several others).

That ranking is not in the standard, but it should drive your planning, because the systems at the bottom fail silently. A guardrail that is missing is visible from the ground. A monitor who has become distracted looks exactly like a monitor.

If a project's fall protection plan rests on a monitor, ask two questions. Who relieves them for lunch and for the bathroom? And what happens to the crew during that gap? A plan without an answer is a plan that has one.