OSHA’s Focus Four are the four hazard categories responsible for the majority of construction worker deaths each year: falls, struck-by incidents, caught-in or -between incidents, and electrocutions. In 2024, these four categories combined for over 1,600 fatal work injuries across all industries in the United States, making them the core of OSHA’s construction safety training programs.
Falls: The Leading Killer on Construction Sites
Falls are the single deadliest hazard in construction. In 2024, falls, slips, and trips accounted for 844 workplace fatalities nationwide. The sources range from unprotected roof edges and scaffolding to ladders, holes in flooring, and elevated platforms. Any walking or working surface with an unprotected edge 6 feet or more above a lower level requires fall protection under OSHA’s standards.
That 6-foot threshold is the number most construction workers need to remember. Once you’re working at that height or above, your employer is required to provide guardrail systems, safety nets, or personal fall arrest systems like harnesses. The rule applies broadly: leading edge work, hoist areas, formwork, ramps, excavation edges, roofing, precast concrete erection, residential construction, and areas near wall openings all have specific fall protection requirements.
Falls don’t only happen from extreme heights. A fall from a second-story scaffold or even a short ladder can be fatal, which is why OSHA treats this category with particular urgency in training.
Struck-By Hazards
Struck-by incidents happen when a worker is hit by a moving, falling, flying, rolling, or swinging object. In 2024, being struck by a propelled, falling, or suspended object killed 357 workers. On a construction site, this covers a wide range of scenarios: a brick falling from a scaffold, a load swinging loose from a crane, a piece of lumber kicked back by a saw, or a vehicle backing into a worker on foot.
The four sub-types are straightforward. Falling objects come from elevated work areas or improperly secured loads. Flying objects are generated by tools, machines, or pressurized systems. Swinging objects typically involve cranes, hoists, or suspended loads that shift unexpectedly. Rolling objects include vehicles, pipes, or equipment on slopes that begin to move. Hard hats, high-visibility clothing, and barricades around active work zones are the basic protections, but the real prevention starts with securing materials, inspecting rigging, and maintaining clear communication between equipment operators and ground crews.
Caught-In or Caught-Between Hazards
This category covers situations where a worker’s body is pulled into, compressed by, or trapped between objects. It includes three main scenarios: trench cave-ins, contact with rotating or moving machinery, and being crushed between two objects. In 2024, roughly 293 workers died from caught-in or caught-between incidents, including both equipment-related compressions and structural collapses.
Trench cave-ins are among the most dramatic examples. In one OSHA case study, a worker setting grade at the bottom of a 9.5-foot deep trench was buried when the excavation wall collapsed during shoring installation. Trenches deeper than 5 feet generally require protective systems like shoring, sloping, or trench boxes.
Rotating machinery is equally dangerous and often less visible as a threat. In another documented incident, a worker crawled under an operating water truck to perform diagnostic work, and his shirt collar became caught on a protruding set screw on a rotating pump shaft. Loose clothing, jewelry, long hair, and dangling lanyards near unguarded moving parts all create caught-in risks. Workers have also been pinned between heavy structural components like I-beams and equipment control panels when loads shifted unexpectedly.
The common thread is that these incidents leave almost no time to react. Prevention depends on proper trenching protocols, machine guarding, lockout/tagout procedures before maintenance, and keeping body parts and clothing away from moving components.
Electrocution Hazards
Electrocution killed 130 workers in 2024. On construction sites, the most common sources are overhead power lines, faulty extension cords, and improperly grounded equipment. Unlike many other hazards, electrical contact doesn’t require a dramatic failure to be lethal. Something as routine as moving an aluminum ladder that touches an overhead line, or using a drill plugged into an extension cord with a missing ground prong, can kill instantly.
Overhead and buried power lines carry extremely high voltage, and the weather coating on overhead lines offers zero protection against electrocution. If a worker touches a power line, whether covered or bare, death is the likely outcome. OSHA identifies three primary ways to control power line hazards: maintaining a safe distance, having the utility company de-energize and ground the lines, or having insulated sleeves installed over the lines before work begins.
Improper grounding is the other major killer. When the grounding path in an electrical system is broken or missing, fault current travels through whatever conductor is available, and that conductor is often a worker’s body. In one case, a missing grounding prong on an extension cord allowed an energized wire to make contact with the grounding wire, electrifying a drill’s entire frame. The worker using it became the path to ground. Checking that ground prongs are intact on every cord and tool before use is one of the simplest protections available.
Why OSHA Groups These Four Together
These four categories aren’t random selections. They consistently represent the largest share of preventable construction deaths year after year, and they respond well to basic training and standard safety controls. OSHA’s 10-hour and 30-hour outreach training programs for construction both require dedicated instruction on all four hazards, making them a mandatory part of the curriculum for anyone going through OSHA construction safety training.
The Focus Four framework gives workers and employers a simple mental model for the most likely ways someone gets killed on a job site. Falls alone accounted for roughly 17% of all workplace fatalities in 2024. Struck-by incidents added another 7%, caught-in or caught-between hazards about 6%, and electrocutions about 2.5%. Together, that’s nearly a third of every workplace death in the country, concentrated in scenarios where proper equipment, training, and site management could have changed the outcome.
For workers preparing for an OSHA outreach course, understanding these four categories and the specific situations within each one is the foundation of the entire program. For anyone working in construction, they represent the daily risks most worth paying attention to.