Walking-Working Surfaces and Fall Protection
The four-foot trigger
Under Subpart D (revised in 2016), general industry employees exposed to falls of 4 feet or more to a lower level must be protected. Protection is also required at any height above dangerous equipment, over holes, and on certain surfaces regardless of height. Subpart D is organized as: 1910.22 walking-working surfaces and housekeeping, 1910.23 ladders, 1910.25–.27 dockboards, rope descent, and scaffolds, 1910.28 duty to have fall protection, 1910.29 fall protection systems criteria, and 1910.30 training.
Systems and dimensions
Guardrail systems: top rail at 42 inches ±3 inches, with a midrail; top rail must withstand 200 pounds and midrails 150 pounds. Handrails on stairs are 30 to 38 inches. Covers over floor holes must be secured, marked "HOLE" or "COVER," and support at least twice the intended load. Fixed ladders installed after November 18, 2018 must have a ladder safety system or personal fall arrest system when the climb exceeds 24 feet; cages are no longer acceptable on new ladders. Personal fall arrest systems and their components must be inspected before each use and removed from service after any fall arrest impact.
Traps
A common distractor is the construction trigger (6 feet) - for general industry, use 4 feet. Another is treating the 4-foot rule as applying to portable ladders; portable ladders are governed by use rules (3 feet above the landing, 4:1 set ratio, no moving while occupied), not by a height trigger.
Worked rule of thumb
Ladder setup: for every 4 feet of working height, the base sits 1 foot out (75.5° angle). A ladder reaching a 12-foot eave is set 3 feet from the wall and extends 3 feet above the landing point.