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Course 808: Focus Four - Struck-By Hazards

Safety guides and audits to make your job as a safety professional easier

What is a Struck-by Hazard?

Skylight a worker fell through


Struck-by injuries are produced by an object that forcibly impacts a person. It is important to point out that in construction, struck-by hazards can resemble caught-in or -between hazards.

To determine if an event was a struck-by accident, ask yourself: Was it the impact of the object alone that caused the injury?

When the force of an impact of an object against a worker's body creates the injury, the event is considered as a Struck-by accident. On the other hand, when the injury is created more as a result of being caught, pinned, or crushed in or between objects, the accident is considered as a caught-in or -between event.

Struck-by hazards are categorized as follows:

  • struck-by flying object. Example - a tool flies through the air and hits you.
  • struck-by falling object. Example - a bucket falls and hits you.
  • struck-by swinging object. Example - a hoisted pallet swinging through the air hits you.
  • struck-by moving (ground-level) object. Example - a moving object such as a vehicle hits you.

Click on the buttons below to see more examples of struck-by accidents and a video on what can happen if a grinder wheel explodes.

Accident Types

Safety Memo - The Accident Cascade.

An accident isn't just an event that you can lump into one big category. In reality, there are many different types of accidents. Let's take a look at a partial list.

  • Struck-by: A person is forcefully struck by an object. The force of contact is provided by the object.
  • Struck-against: A person forcefully strikes an object. The person provides the force or energy.
  • Contact-by: Contact by a substance or material that, by its very nature, is harmful and causes injury.
  • Contact-with: A person comes in contact with a harmful substance or material. The person initiates the contact.
  • Caught-on: A person or part of his/her clothing or equipment is caught on an object that is either moving or stationary. This may cause the person to lose his/her balance and fall, be pulled into a machine, or suffer some other harm.
  • Caught-in: A person or part of him/her is trapped, or otherwise caught in an opening or enclosure.
  • Caught-between: A person is crushed, pinched or otherwise caught between a moving and a stationary object, or between two moving objects.
  • Fall-to-surface: A person slips or trips and falls to the surface he/she is standing or walking on.
  • Fall-to-below: A person slips or trips and falls to a level below the one he/she was walking or standing on.
  • Overexertion: A person over-extends or strains himself/herself while performing work.
  • Bodily reaction: Caused solely from stress imposed by free movement of the body or assumption of a strained or unnatural body position. A leading source of injury:
  • Overexposure: Over a period of time, a person is exposed to harmful energy (noise, heat), lack of energy (cold), or substances (toxic chemicals/atmospheres).

Struck-by Accident Types

  • Four workers were installing signs on a highway when a pick-up truck changed several lanes and entered the work area. The truck struck one of the workers, knocking him off the road and over a bridge rail. He fell approximately 18 feet and died.
  • Four workers were struck by an exterior wall while attempting to lift it in place. Three of the workers received bruises and contusions. One of the workers received a fractured leg and was hospitalized.
  • A construction inspector was crossing an equipment vehicle route at an interstate highway bridge construction site. He walked into the path of the end loader traveling the route, was run over, and killed. The loader operator was unaware that he struck the inspector.
  • A worker was struck by the counterweight and revolving superstructure of an excavator when he walked between the excavator and a hillside.
  • Workers were pulling 60-foot sections of pipe out of a hole, using a hoist to stack them on the derrick floor. One of the workers let go of a pipe section before it was secured. As he bent over, the pipe swung around and struck him on the head, killing him.
  • A worker was maneuvering an overhead crane when a metal plate, weighing approximately 7,330 lbs., separated from the lifting clamp and fell, striking and killing the worker.

Read the material in each section to find the correct answers to each of the questions. After answering all questions, click the "Check Quiz Answers" button to see your score and a list of missed questions. To correct a question, return to the question, review the material, change your answer, and return to the last section page. Click the "Check Quiz Answers" again to recheck the results.

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Note: Videos and exercises in our courses are for information only and not required to view. Final exam questions will not be derived from the videos. OSHAcademy is not responsible for video content.

1. Which of the following describes a struck-by accident?

a. A worker is contacted by electrical energy
b. A rotating crane crushes a worker
c. A worker contacts an hot surface
d. A flying bucket hits a worker

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All-Industry Fatalities

According to Bureau of Labor Statistics (BLS), across all industries, a total of 5,250 fatal occupational injuries occurred in 2018. About 11% (566) of all fatalities were due being struck by objects and equipment.

Construction Fatalities

In 2018, a total of 1,008 fatalities occurred in all construction occupations. About 11% (112) of all construction fatalities were due to struck-by object or equipment accidents.

Over 50% of the struck-by fatalities in construction were due to being struck by falling objects or equipment, followed by being struck by vehicles -non-transport that accounted for about 23% of the total.

You can review the BLS statistics on Table A-9, Fatal occupational injuries by event or exposure for all fatal injuries and major private sector, all United States, 2018.

2. Most struck-by fatalities in construction were caused by being struck by _____.

a. swinging or slipping objects
b. vehicles tipping over
c. rolling objects or equipment
d. falling objects or equipment

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Struck by Falling Objects or Equipment

A person is struck-by a falling object or equipment when crushed, pinned, or caught under an object or equipment that has fallen from above. This accident type does not include the collapse of material or structures.


  • A worker was tearing down a transmission structure using a digger-derrick when a pole broke and struck him on the head.
  • A worker was struck by a load of wall panels that fell off his truck.
  • Four workers rebuilding a bridge that had washed out by floods were injured when a crane boom cable broke, and the boom fell on them.
  • A worker was engaged in cutting a boiler in sections with a cutting torch. The section being cut fell off allowing the remaining section to flip over onto its bottom and land on the worker.
  • A worker was assisting a rigger who had attached a load to the block hook of a wheel mounted crane. The crane operator was positioned in the cab and waiting for the hand signal to make the lift. During this process, the jib of the crane fell from its stowed position on the boom and struck the worker.

Practice Identifying Hazards

Try to identify the hazards in each picture below. Then click on each picture to see if you correctly identified the hazards.

Read about a real-world accident

Fall from tilt-up concrete wall

Description of Accident

Ball and socket connectors are used to attach conductor stringing blocks to insulators on the arms of 90-foot metal towers of electrical transmission lines. Normally stainless steel cotter keys secure the ball and socket connector in place. In this case, however, black electrical tape was wrapped around the socket to keep the ball in place rather than a cotter key. The tape apparently stretched, and the ball came loose, dropping the stringing block approximately 90 feet onto the head of an employee below, one of a four-man erection crew.

What would you recommend?


  • Rigging and equipment must be regularly inspected and maintained in safe operating condition as required by general provisions of OSHA's construction (29 CFR 1926.959).
  • Employees must be instructed to recognize and avoid unsafe conditions. They must also be made aware of regulations that apply to the work and the work area, which eliminate safety and health hazards as required in the safety training and education section of OSHA's construction safety standards (29 CFR 1926.21(b)(2)).

3. Struck-by falling object or equipment accidents include all of the following EXCEPT _____.

a. material falling off decks or roofs
b. scaffolds collapsing
c. objects falling off scaffolds
d. equipment falling off moving vehicles

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Struck by Flying Object

A Struck by flying object hazard exists when something has been thrown, hurled, or is being propelled through space. It can include instances when a piece of material separates from a tool, machine or other equipment, striking a worker, resulting in injuries or fatality.

Also, a hazard exists if an object is ejected under power by a tool or equipment. An example of this would be a nail gun, which propels a nail from the gun by force; it is discharged. This force can be either pneumatic or powder-actuated. Powder-actuated tools are particularly hazardous due to the force behind the fastener. These fasteners are designed to go through wood, concrete and steel, and they can certainly go through a worker. To learn more about nail gun safety, see OSHAcademy Course 611, Nail Gun Safety.

Using compressed air can also cause flying object hazards. Compressed air is commonly used to power tools and clean surfaces.

Practice Identifying Hazards

Try to identify the hazards in each picture below. Then click on each picture to see if you correctly identified the hazards.

Struck-by Flying Objects Hazard
Click image to review hazards

Struck-by Flying Objects Hazard
Click image to review hazards

Struck-by Flying Objects Hazard
Click image to review hazards

Let’s review an example of an actual accident:

Examples of accidents that can result from struck-by flying object hazards:
  • A worker was removing a frozen bolt from the track of a caterpillar front end loader and was struck-by a bolt that entered his forehead.
  • A worker was freeing a pump component under pressure and was impaled by the pump component.
  • A worker was killed when a blast of compressed air from a gas pipeline struck him. A compressor was started to fill the pipeline with compressed air in an effort to push out a "pig." when the pipeline suddenly cleared, an employee was still in the way and was killed. Before the compressor was started the area should have been cleared.
  • The victim was in the process of using an 8-foot step ladder to gain height to nail a strap onto a residential home single story construction project. The victim used a nail gun with a 3 ½ inch nail to affix the strap to the exterior wall. Using his right hand for the gun, he leaned over to the left and tried to place a nail into the strap. The nail ricocheted and hit him on the left side of his head just above the left ear. He fell to the ground and eventually passed out. Fellow workers transported him to the hospital. He died approximately two days later.

Fall from tilt-up concrete wall

Description of Accident

A carpenter apprentice was killed when he was struck in the head by a nail that was fired from a powder-actuated tool. The tool operator, while attempting to anchor a plywood form in preparation for pouring a concrete wall, fired the gun causing the nail to pass through the hollow wall. The nail traveled some twenty-seven feet before striking the victim. The tool operator had never received training in the proper use of the tool, and none of the employees in the area was wearing personal protective equipment.

What would you recommend?


  • Institute a program for frequent and regular inspections of the job site, materials, and equipment by a competent person(s) (1926.20(b)(2)).
  • Require employees exposed to the potential hazards associated with flying nails to use appropriate personal protective equipment. (1926.100(a) and 1926.102(a)(1)).
  • Train employees using powder actuated tools in the safe operation of the particular tool (1926.302(e)(2)).
  • Train employees operating powder actuated tools to avoid firing into easily penetrated materials (1926.302(e)(8)).

4. Which of the following accidents may occur if a worker is struck by an object ejected from a tool under power?

a. Struck by swinging object
b. Struck by falling object
c. Struck by flying object
d. Struck by rolling object

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Struck by Swinging Object

When materials are mechanically lifted, they have the potential to swing and strike workers. As the load is lifted, the materials may swing, twist or turn. This movement can catch workers by surprise, and the swinging load could hit them.

Windy conditions are especially hazardous because the load will swing more. Depending on where the worker is standing and the force behind the load, the worker may fall to another level after being struck and sustain even greater injuries. Swinging, loads can also slip from their riggings and strike workers. Loads must be rigged properly to prevent slipage.

When the source of injury has been referred to objects that are not free standing, they are attached at some point or are being held by the worker. This includes instances where a hinge-like motion retracts creating swinging motion in which the worker is struck-by a slamming or swinging motion.


  • A worker was working within the swing radius of a barge-mounted crane used in dredging operations. He was hit and killed.
  • Two workers were assigned to use a crane to set up on a ground slab at the corner of a building. The 24-piece bundle of rebar was to be picked up and loaded onto the crane's hoist line 50 ft in front of the crane. The operator made the pick-up and was swinging around and lowering it to his left using hand signals when the right pennant line broke at the yoke/bridle. The boom collapsed, striking one of the workers on the head and killing him.

Practice Identifying Hazards

Try to identify the hazards in the picture below. Then click on the picture to see if you correctly identified the hazards.

5. What condition is especially hazardous when a crane lifts a load?

a. Illumination
b. Noise
c. Rain
d. Wind

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Struck by Moving (Worker-Level) Object

Being struck-by a moving object is when an object is rolling, moving, or sliding on the same level at which the worker is located. It includes instances in which the worker is:

  • struck or run over by a moving vehicle without being caught under it, or
  • instances in which the worker is struck-by a sliding object or equipment on the same level.


Click on the button below to see more examples of struck-by-moving-object accidents.

  • While walking along the track, a worker was struck by an unmanned rail car at an airport.
  • A worker (security guard) was struck by a tractor trailer and dragged, resulting in fatal injuries.
  • A worker suffered fatal injuries after being struck by a moving semi-truck while loading/unloading freight.
  • A worker was performing repair operations on an impact attenuator and was struck by a truck.
  • A worker was flagging traffic and was struck by a truck.
  • A four-person ground crew was working with a mobile under-hung bridge crane. The crane ran over one of the crew members, who had walked too close to the wheel of the crane. The employee died from his injuries.
  • A worker was setting traffic cones for a paving project. A steel wheel roller was compressing the asphalt, and the traffic cones were being moved so that they would be in the path of the roller. He was pronounced dead at the hospital.

Practice Identifying Hazards

Try to identify the hazards in each picture below. Then click on each picture to see if you correctly identified the hazards.

6. A struck-by-moving-object accident includes instances in which the worker is _____.

a. struck and caught under a tractor
b. struck and run over by a car driving by
c. struck and pinned by a moving crane
d. struck and crushed under the vehicle

Check your Work

Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.

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