STRUCK-BY HAZARDS: THE SECOND LEADING CAUSE OF CONSTRUCTION DEATHS

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Falls get the most attention — and for good reason. But struck-by incidents are one of the leading causes of fatalities on construction sites in Ontario and across North America. According to WSIB data, struck-by injuries consistently account for a significant portion of critical injuries and deaths in Ontario's construction sector every year. A wrench dropped from the 10th floor, a backhoe swinging its bucket into a worker, a piece of formwork blown off a scaffold by wind — these incidents happen fast and the consequences are devastating.

Understanding the types of struck-by hazards, where they occur, and how to prevent them is essential for every construction worker on every site.

The Numbers in Ontario

WSIB data shows that construction consistently leads all sectors in Ontario for traumatic workplace fatalities, and struck-by incidents are a major contributor. In 2022, construction accounted for 31 percent of Ontario's 90 traumatic workplace fatalities, the largest share of any sector.

The most common struck-by fatalities involve heavy equipment (excavators, dump trucks, loaders), falling objects from elevation, and crane loads. Critical injuries from struck-by incidents are even more common — workers who survive often face permanent disabilities including traumatic brain injuries, crushed limbs, spinal damage, and internal organ injuries.

The 4 Types of Struck-By Hazards

Struck-by hazards fall into four categories. Recognizing which type applies to your work situation helps you choose the right prevention measures:

1. Struck by Flying Objects

Flying objects are materials or fragments propelled through the air by force — power tools, pneumatic equipment, saws, grinders, or explosive-actuated tools. Concrete chips from a chipping hammer, a nail from a powder-actuated tool that penetrates a wall and exits the other side, metal fragments from a cut-off saw — all of these are flying object hazards.

• Prevention: Always wear impact-rated safety glasses or goggles when operating or working near power tools. Use guards on grinders and saws. Check the area behind walls and surfaces before using powder-actuated tools. Erect debris screens when chipping or grinding near other workers.

2. Struck by Falling Objects

This is the most common type of struck-by incident on construction sites. Anything above you that is not secured can become a falling object — tools, materials, equipment, building components, or debris. Even a small bolt dropped from height can seriously injure a worker below.

Ontario Regulation 213/91 (Construction Projects) section 34 requires overhead protection wherever material may fall on a worker, at every means of access to a building under construction and above every area where work is being done. Other controls include toe boards on guardrails (minimum 89 mm high), debris netting, tool lanyards, and canopy structures over pedestrian access routes.

• Prevention: Install toe boards and guardrails with mid-rails on all elevated platforms. Use debris netting on scaffolding. Tether all tools and materials when working at heights — tool lanyards, retractable tool tethers, and secured tool pouches are not optional when you are working above other people. Establish controlled access zones below overhead work. Never stack materials near open edges.

Even a small bolt dropped from height can seriously injure a worker below. Secure every tool and piece of material at height — toe boards, tool lanyards, and debris nets are not optional when workers are below.

3. Struck by Swinging Objects

Swinging objects are loads that move in an arc — crane loads, excavator buckets, concrete pump booms, suspended scaffolds, and any material being hoisted or moved by mechanical means. The danger is in the swing radius. A crane load that looks stationary can swing several metres when the crane slews, when wind picks up, or when the load is released from a snag.

In Ontario, one of the most tragic recurring scenarios involves workers being struck by excavator booms and buckets. The operator's blind spots combined with the wide swing radius create a deadly zone that workers often underestimate.

• Prevention: Never stand in the swing radius of a crane, excavator, or other rotating equipment. Establish exclusion zones and mark them with barricades, tape, or signage. Use a dedicated signaller when loads are being moved near workers. Rig loads properly so they do not swing — use tag lines to control suspended loads. Never walk under a suspended load for any reason.

4. Struck by Rolling Objects

Rolling objects include pipes, conduit, barrels, cylindrical materials, equipment on wheels, and vehicles. On sloped surfaces, unsecured round materials can roll unexpectedly. In roadwork zones, vehicles entering the work area are a constant rolling-object threat. On laydown areas, improperly stored pipes and conduit can shift and roll when disturbed.

• Prevention: Chock and wedge all cylindrical materials stored on slopes. Use pipe racks with proper restraints. In roadwork zones, use concrete barriers (not just pylons) to separate workers from traffic. Never store round materials on sloped ground without positive restraint. On active sites with vehicle traffic, establish dedicated pedestrian walkways separated from vehicle routes.

Exclusion Zones Around Heavy Equipment

Heavy equipment is involved in a disproportionate number of struck-by fatalities. Excavators, backhoes, loaders, dump trucks, and cranes all have blind spots where the operator simply cannot see a worker — even with mirrors and cameras.

Ontario Regulation 213/91 section 104 addresses the safe operation of vehicles and equipment on construction sites. The regulation requires projects to be planned so vehicles and equipment reverse as little as possible, and requires a signaller to assist the operator whenever the operator's view of the intended path of travel is obstructed or a person could be endangered by the equipment or its load. Signallers must be used when equipment is operating near workers, particularly during backing operations.

• Establish clear exclusion zones: The minimum exclusion zone around heavy equipment should be the full swing radius of the machine plus a safety margin. For an excavator, this is typically the full reach of the boom in all directions.
• Use signallers and spotters: A dedicated signaller must be used whenever a vehicle or piece of equipment is backing up in areas where workers are present. The signaller must have a clear view of both the operator and the area behind the equipment.
• High-visibility clothing: Ontario Regulation 213/91 section 69.1 requires every worker who may be endangered by vehicular traffic to wear a fluorescent blaze or international orange garment covering at least the upper body, with retro-reflective, fluorescent yellow stripes. Signallers must wear the same garment. This is not optional — it is law.
• Communication: Make eye contact with operators before entering their work area. If you cannot see the operator, assume the operator cannot see you. Use two-way radios on large sites with multiple pieces of equipment operating simultaneously.

Tool Tethering at Heights

When you are working above other people, every tool and piece of material you carry is a potential struck-by hazard for the workers below. A 1 kg wrench dropped from 10 metres generates approximately 100 joules of kinetic energy on impact — enough to cause a fatal head injury even through a hard hat.

• Tool lanyards: Attach all hand tools to your harness or belt using rated tool lanyards. Coiled lanyards work well for frequently used tools. Retractable lanyards are better for heavier tools.
• Tool pouches and holsters: Close-topped pouches prevent tools from falling out when you bend over or lean forward. Open-topped tool belts are a constant risk at elevation.
• Material handling: Use hoisting equipment to move materials to elevation — do not carry loose materials up ladders. Secure all materials on elevated platforms so they cannot be dislodged by wind, vibration, or accidental contact.
• Barricades below: Establish a controlled access zone directly below all overhead work. Barricade the area with caution tape at minimum, and use hard barricades for high-risk operations like steel erection or concrete forming.

PPE for Struck-By Protection

Personal protective equipment is the last line of defence against struck-by hazards. It does not eliminate the hazard — it reduces the severity of injury if all other controls fail:

• Hard hats: Hard hats are mandatory at all times on Ontario construction projects, and the shell must withstand a 20,000-volt dielectric test. From July 1, 2027, they must also meet CSA Z94.1 or ANSI Z89.1, with Type 2 (top and lateral impact) protection where workers face side-impact hazards. Replace any hard hat that has taken an impact — the shell absorbs energy by deforming, and it cannot do that twice. Replace hard hats every 5 years regardless of visible condition, as UV exposure degrades the shell material.
• High-visibility clothing: Class 2 or Class 3 high-visibility vests or jackets ensure operators can see you. Required under Ontario Regulation 213/91 for workers who may be endangered by vehicular traffic, and for signallers.
• Safety glasses and goggles: Impact-rated eye protection (CSA Z94.3) for flying object hazards. Use goggles for grinding, chipping, and overhead work where debris can enter from above and around regular glasses.
• Safety footwear: CSA Grade 1 safety boots with steel or composite toe caps protect against falling and rolling objects striking your feet.
• Face shields: For high-energy flying debris from cutting, grinding, or demolition operations. Worn over safety glasses, not as a replacement for them.

Typical Struck-By Incidents

These examples illustrate how struck-by hazards cause injuries and deaths on construction sites:

• Falling formwork panel: A formwork panel being stripped from a concrete wall fell and struck a worker below who was not wearing a hard hat and was working inside what should have been a controlled access zone. The zone had not been established. The worker suffered a traumatic brain injury.
• Excavator swing: A worker walked behind an excavator that was backfilling a trench. The operator swung the bucket to load a dump truck and struck the worker, who was inside the machine's blind spot. No signaller was in place. The worker was killed.
• Dropped tool: An ironworker's spud wrench fell from an elevated work platform and struck a labourer on the ground. The tool was not tethered and the area below was not barricaded. The labourer suffered a skull fracture.

Every one of these incidents was preventable with standard controls — exclusion zones, tool tethering, signallers, barricades, and PPE.

The Bottom Line

Struck-by hazards are everywhere on construction sites. They involve heavy equipment, falling tools, swinging loads, and rolling materials. The controls are straightforward — exclusion zones, barricades, tool tethering, signallers, and proper PPE. None of them are complicated. All of them are required. The workers who get hurt are almost always the ones who were in a zone they should not have been in, or who were not protected by controls that should have been in place.

Stay out of the line of fire. Tether your tools. Respect exclusion zones. Wear your hard hat. These are not suggestions — they are what keeps you walking off the site at the end of the day.