OSHA’s Focus Four hazards are falls, struck-by incidents, caught-in or caught-between incidents, and electrocution. These four categories are singled out because they account for the majority of construction worker deaths each year. In 2009, they were responsible for nearly three out of five fatal injuries on construction sites, and they remain the core safety emphasis in OSHA’s outreach training programs today.
Falls
Falls are consistently the leading killer in construction. In 2023, about one in five workplace deaths occurred in the construction industry, and 38.5% of those deaths were caused by falls, slips, and trips. The most common scenarios involve unprotected edges, floor openings, and improperly used or positioned ladders and scaffolding.
OSHA requires fall protection at different heights depending on the work setting. In construction, the trigger is six feet above a lower level. General industry workplaces require protection at four feet, shipyards at five feet, and longshoring operations at eight feet. When you’re working over dangerous equipment or machinery, fall protection is required regardless of how far you could fall. Guardrails, safety nets, and personal fall arrest systems (harnesses attached to anchor points) are the primary protective measures.
Struck-By Hazards
A struck-by incident happens when a worker is hit by a moving or flying object and the force of that impact alone causes the injury. This is one of the key distinctions OSHA draws: if the object strikes you and the impact itself is what hurts you, it’s a struck-by event. The three most common sources are vehicles, falling or flying objects, and collapsing masonry walls.
Vehicle-related struck-by incidents include being hit by trucks, pinned between construction vehicles and walls, or struck by swinging backhoe arms. On busy sites with heavy equipment moving in tight spaces, these risks multiply quickly.
Falling and flying objects are a hazard any time you’re working beneath cranes, scaffolds, or areas where overhead work is happening. Objects can also become airborne from power tool use or from the sudden release of tension, such as when a wire rope snaps or a wedged object breaks free. OSHA case files include incidents where unsecured ladder sections fell from scaffolds, snapping cables struck workers, and nails fired from powder-actuated tools passed through walls and traveled dozens of feet. Hard hats, toe boards, debris nets, and tool-tethering systems are basic protective measures for these scenarios.
Caught-In or Caught-Between Hazards
Caught-in or caught-between hazards involve a worker being squeezed, crushed, pinched, or compressed between two or more objects, or pulled into moving machinery. The critical difference from a struck-by event is that the injury comes from crushing force between objects rather than from the impact of a single object. Getting clothing or a limb pulled into running equipment, being compressed between a rolling trailer and a dock wall, or being buried in a trench cave-in all fall into this category.
Trench cave-ins are among the most deadly caught-in scenarios. Soil is heavy, and even a partial collapse can trap and suffocate a worker within minutes. OSHA requires a protective system (sloping, shoring, or shielding) for any trench five feet deep or greater, unless the excavation is entirely in stable rock. Trenches 20 feet deep or greater must have a protective system designed by a registered professional engineer. Despite these clear requirements, cave-in deaths persist because employers skip protective measures or rush the work.
Other caught-between situations include being crushed under overturning equipment, pinned between a piece of machinery and a fixed structure, or trapped when unsupported walls collapse. In one OSHA case report, a worker operating a road grader jumped from the machine when it stalled and began to roll, only to be pulled under and crushed by the tires. In another, a worker in an aerial lift was pinned between the lift’s control panel and an overhead I-beam after accidentally engaging the drive lever.
Electrocution
Electrocution on construction sites most commonly involves contact with overhead or buried power lines, lack of ground-fault protection, and improper use of extension cords. Power lines carry extremely high voltage, and fatal electrocution is the primary risk, though severe burns and falls from elevation (when the shock causes a worker to lose their grip) are also common outcomes.
OSHA sets specific clearance distances that equipment must maintain from power lines. For lines carrying up to 50 kilovolts, the minimum distance is 10 feet. That increases to 15 feet for lines up to 200 kV, 20 feet for up to 350 kV, and 25 feet for up to 500 kV. On a practical level, this means crane operators, workers on aerial lifts, and anyone moving tall equipment or materials need to know the voltage of nearby lines and stay well clear.
Ground-fault protection is the second major concern. Construction environments are rough on electrical equipment. Normal use causes insulation breaks, short circuits, and exposed wires. Without ground-fault circuit interrupters (GFCIs), a fault can send current through a worker’s body instead of safely routing it to the ground. Extension cords that aren’t three-wire type, aren’t rated for heavy use, or have been damaged or modified create similar risks. Inspecting cords before each use and using GFCIs on all temporary power circuits are standard protective steps.
How the Focus Four Fits Into OSHA Training
The Focus Four hazards form a required block of instruction in OSHA’s Outreach Training Program, which includes the widely recognized 10-hour and 30-hour construction safety courses. These courses must be taught over a minimum of two calendar days for the 10-hour class and four calendar days for the 30-hour class. Each Focus Four hazard is covered as its own segment within a dedicated four-hour training block, giving workers the ability to recognize these hazards before they set foot on a job site.
Beyond the outreach courses, the Focus Four framework serves as a practical risk assessment tool. If you’re a site supervisor or safety officer scanning a worksite for the most likely sources of fatal injury, these four categories cover the vast majority of what could kill someone that day. That concentrated focus is the whole point: rather than trying to address every possible hazard equally, the Focus Four directs attention to the scenarios that consistently produce the most deaths.