The Fatal Four: Recognizing and Controlling Leading Hazards

The Fatal Four: Recognizing and Controlling Leading Hazards

Every year, thousands of construction workers are seriously injured or killed on the job. OSHA has identified four hazard categories—commonly called the Fatal Four—that together account for the majority of construction fatalities in the United States. Understanding these categories and knowing how to control them is a core expectation for every worker on every jobsite, and it is central to both your NCCER Core credential and your OSHA 10 card.

The Four Categories

Falls are the leading cause of construction fatalities. They occur from scaffolds, ladders, roofs, floor openings, and leading edges. A fall can be fatal even from a relatively low height. OSHA requires fall protection whenever workers are exposed to a fall of six feet or more in construction.

Struck-by hazards occur when a worker is hit by a moving object—a swinging crane load, a vehicle backing up, flying debris from a grinder, or materials ejected from equipment. Workers must stay out of swing-radius zones and wear high-visibility vests near vehicle traffic.

Caught-in/between hazards result when a worker is caught, squeezed, crushed, or entangled between objects. Examples include unguarded rotating equipment, cave-ins in unprotected trenches, and a worker caught between a piece of equipment and a fixed structure. Trench cave-ins are among the most deadly caught-in events because they happen suddenly and a cubic yard of soil can weigh close to a ton.

Electrical hazards include contact with overhead power lines, energized tools, damaged cords, and improper grounding. Electrocution can kill instantly. Before any excavation or digging begins, underground utilities must be located by calling 811. Overhead lines must be treated as energized unless confirmed de-energized by the utility.

The Hierarchy of Controls

Knowing the hazard is only the first step. OSHA and NCCER both teach the hierarchy of controls as the structured method for reducing risk. Apply controls from the top of the hierarchy downward; higher-level controls are more effective because they do not depend on worker behavior.

1. Elimination – Remove the hazard entirely. Example: reschedule overhead work so no workers are below.

2. Substitution – Replace the hazard with something less dangerous. Example: use a scissor lift instead of a portable ladder for extended overhead work.

3. Engineering controls – Use physical means to isolate workers from the hazard. Example: install guardrails and toeboards on a scaffold; use a trench box in an excavation.

4. Administrative controls – Change work procedures or schedules. Example: establish an exclusion zone under crane lifts; use a spotter for backing vehicles; conduct toolbox talks on electrical safety.

5. PPE (Personal Protective Equipment) – Provide equipment worn by the worker as a last line of defense. Example: hard hat, safety-toe boots, high-visibility vest, safety glasses, a personal fall arrest system (PFAS) with harness and lanyard.

PPE never eliminates the hazard—it only reduces injury if the hazard occurs. Always select PPE appropriate to the specific hazard (e.g., a Class E hard hat for electrical hazards, not just any hard hat).

Applying the Hierarchy to Each Fatal Four Category

Falls: Elimination—design flat accessible work areas. Substitution—prefabricate components at ground level. Engineering—guardrail systems, safety nets, covers over floor openings. Administrative—written fall protection plan, training, buddy checks. PPE—full-body harness, shock-absorbing lanyard, anchor point rated at 5,000 pounds per worker.

Struck-by: Elimination—redesign material delivery to avoid overhead lifts near workers. Substitution—use conveyors instead of throwing materials. Engineering—debris nets, barricades, tool tethers at height. Administrative—hard-hat zones, spotter requirements, exclusion zones. PPE—hard hat, safety glasses, high-visibility vest.

Caught-in/between: Elimination—trench design to avoid open excavations. Substitution—use trenchless technology. Engineering—trench boxes, sloping or shoring, machine guards on equipment. Administrative—daily competent-person inspections of excavations, lockout/tagout (LOTO) before servicing equipment. PPE—snug-fitting clothing (never loose sleeves near rotating parts), safety glasses, hearing protection near machinery.

Electrical: Elimination—de-energize and verify before work begins (LOTO). Substitution—use battery-powered tools instead of cord-connected tools near water. Engineering—ground fault circuit interrupters (GFCIs) on all temporary power, assured equipment grounding conductor program. Administrative—safe approach distances to overhead lines, pre-task utility locates. PPE—insulated gloves rated for the voltage, Class E hard hat, non-conductive footwear.

Lockout/Tagout (LOTO)

Any time equipment is serviced or guarded, energy must be controlled. LOTO requires isolating every energy source—electrical, hydraulic, pneumatic, gravitational—locking the isolation point with a personal lock, and verifying zero energy before work begins. Each worker places their own lock; no one removes another worker's lock.

Competent Person Requirement

OSHA standards for excavations, scaffolds, and fall protection require a competent person—someone who can identify hazards and has authority to correct them—to inspect these systems regularly. As a new worker, you must know when to stop work and notify your competent person if you observe a hazard.

Key Takeaway

Recognizing which Fatal Four category a hazard belongs to directs you immediately to the right family of controls. Pair that recognition with the hierarchy of controls, and you have a repeatable, professional approach to keeping everyone on your site safe.