Struck-By, Caught-Between, and Line-of-Fire Controls

Struck-By, Caught-Between, and Line-of-Fire Controls

Struck-by and caught-between events often look sudden, but the conditions usually develop in plain sight. A suspended bundle begins to drift, a loader backs into a blind corner, a stack leans after one piece is removed, or a pressure line is opened without controlling stored energy. The CHST role is to recognize where a worker could be hit, pinned, crushed, or trapped, then require controls before the task depends on luck, speed, or shouted warnings.

Identify the Energy and the Path

Line of fire is the path an object, load, tool, vehicle, material, or released force will travel if control is lost. The question is not only what is moving now, but what could move if a chain breaks, a sling slips, a trench wall shifts, a tire rolls, a form panel kicks, or a hydraulic component releases pressure. Caught-between exposure exists when the worker has no escape space between two objects, such as a wall and a reversing truck, a rotating superstructure and a fixed column, or a suspended load and a deck edge.

A practical field scan should cover four categories:

• Moving equipment: trucks, forklifts, loaders, excavators, compactors, telehandlers, and skid steers.
• Moving loads: suspended picks, pushed material, rolling pipe, stacked bundles, buckets, forks, and crane blocks.
• Stored energy: compressed air, hydraulic pressure, springs, gravity, tensioned cable, and unstable soil or material.
• Dropped objects: hand tools, deck materials, formwork components, scaffold parts, and loose hardware.

Controls That Work in the Field

The preferred control is separation. Install barricades, cones, flagging, warning lines, hard barricades, gates, or controlled access zones based on the force involved. A soft cone line may be enough for pedestrian routing around a low-risk storage area, but it is not adequate where workers could be struck by a swinging concrete bucket or counterweight. Use hard barricades or a controlled access point when the consequence is severe.

Communication and Stop-Work Triggers

Communication must be specific. Phrases such as watch out or be careful do not create control. Use positive confirmation: who is moving, where they will move, who signals, what radio channel or hand signals are used, and what command stops the work. For mobile equipment, the spotter and operator should agree on stop signals before movement begins. If visual contact is lost, the equipment stops.

Stop work when an exclusion zone is missing, a spotter is distracted, workers walk under a suspended load, material is not secured against rolling or falling, a reversing path is shared with pedestrians, or two crews create crossing lines of fire. Stopping the task is not a paperwork event; it is a field control used when the present setup cannot protect people.

CHST Field Decisions

A CHST should challenge work plans that place the worker in the pinch point to make the task faster. Examples include guiding a load by holding the bottom edge, standing between a truck and a dock, stepping behind equipment to move a cone, or reaching into a nip point to clear debris. The better decision is to redesign the task: use push poles, tag lines where they do not create entanglement, remote release devices, blocking, equipment repositioning, or sequencing changes.

Inspection also matters. Loose guardrails, damaged barricades, missing backup alarms, broken mirrors, unsecured tools at height, weak stack cribbing, or inoperative radios are early warnings that the struck-by system is failing. The CHST should document the correction, but the immediate goal is to remove the exposure now.

Exam Focus

For the CHST exam, expect scenarios where several answers sound reasonable. The best answer usually controls the hazard at the source or separates workers from the hazard before relying on PPE. Hard hats, high-visibility garments, and safety glasses are important, but they do not make it acceptable to stand under a load, walk through a backing zone, or work inside a crush point.