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Course 807: Focus Four - Caught In-Between Hazards

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

Protective Measures

The employer is required by OSHA standards to perform a number of actions to protect workers from caught-in between hazards. Click the button below to see a summary of the requirements.

  • Provide guards on power tools and other equipment with moving parts
  • Support, secure or otherwise make safe equipment that has parts that workers could be caught between
  • Take measures to prevent workers from being crushed by heavy equipment that tip over
  • Take measures to prevent workers from being pinned between equipment and a solid object
  • Protect workers during trenching and excavation work
  • Provide means to avoid the collapse of structures scaffolds
  • Provide means to avoid workers' being crushed by collapsing walls during demolition or other construction activities
  • Designate a competent person
  • Provide training for workers

Use Properly Guarded Machinery

Moving machine parts have the potential to cause severe workplace injuries, such as crushed fingers or hands, amputations, burns, or blindness. Any machine part, function, or process that may cause injury must be safeguarded.

Hazardous Motions and Actions

Different types of hazardous mechanical motions and actions in varying combinations are required to automate tools, equipment, and machinery. Recognizing the hazards they present is the first step toward protecting workers from the danger these motions and actions present. There are three basic hazardous motions and associated actions that can injure employees when exposed.

Click on the button below to see the basic types of hazardous mechanical motions and actions.


  • Rotating - a circular motion around an axis or center such as a rotating shaft.
  • Reciprocating - a push-and-pull motion common to saws.
  • Transversing - a continuous straight-line movement typical of moving belts.


  • cutting - Cutting action may involve rotating, reciprocating, or transverse motion at the point of operation (circular saws, band saws, drills, etc.).
  • Punching - Punching action results when power is applied to a slide (ram) for the purpose of blanking, drawing, or stamping metal or other materials.
  • Shearing - Shearing action involves applying power to a slide or knife in order to trim or shear metal or other materials.
  • Bending - Bending action results when power is applied to a slide in order to draw or stamp metal or other materials.

Click on the button below to see some examples of reciprocating, rotating, or traversing parts that OSHA requires to be guarded if exposed to contact by workers.

These parts include the movement of rotating members, reciprocating arms, moving belts, meshing gears, cutting teeth, and any parts that impact or shear. These different hazardous mechanical motions and actions are basic in varying combinations to nearly all machines, and recognizing them is the first step toward protecting workers from the danger they present.

A wide variety of mechanical motions and actions may present hazards to the worker.
  • belts;
  • gears;
  • shafts;
  • pulleys;
  • sprockets;
  • spindles;
  • drums;
  • flywheels; and
  • chains.

For more information on machine safeguarding, see OSHAcademy Course 726, Introduction to Machine Guarding.

1. Which hazardous motion is a push-and-pull motion common to saws?

a. Reciprocating
b. Rotating
c. Cutting
d. Transversing

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Use Properly Guarded Machinery (Continued)

Use Guards on Tools and other Equipment with Moving Parts

The employer must ensure hand-held power tools are fitted with guards and safety switches. The type of guard will be determined by the power source of the tool (electric, pneumatic, liquid fuel, hydraulic, or powder-actuated). Click on the button below to see examples.

  • Exposed moving parts of power tools, such as belts, gears, shafts, pulleys, etc. must be guarded.
  • Points-of-operation, where the work is actually performed on the materials, must also be guarded.
  • Power saws are a primary type of equipment which requires a point-of-operation guard.
  • In-running nip points, such as where the sanding belt runs onto a pulley in a belt sanding machine, must also be guarded.

Woman partially scalped by rotating belt.

Protective Clothing, Jewelry, and Long Hair

Be sure to remove personal protective equipment, loose clothing, and jewelry to prevent being caught by moving parts. Cover your hair because this can also create a hazard. A protective glove can become caught between rotating parts causing multiple serious injuries or death. Long hair can get caught in rotating parts, pulling the worker into the machinery. Jewelry and loose clothing can catch on machine parts causing amputation or serious injury by pulling the hand/body into the machinery.

Use Other Methods to Secure Machinery

Use other methods to ensure that machinery is sufficiently supported, secured or otherwise made safe. Make sure your equipment is de-energized and cannot be started accidentally by using lockout/tagout procedures.

Click on the button below to see a list of safe practices to make sure equipment energy sources are controlled.

  • Disconnect tools when not in use, before servicing, and when changing accessories such as blades, bits, and cutters.
  • Turn off vehicles before you do maintenance or repair work.
  • If possible, lockout the power source to the equipment. The type of power source may be electric, pneumatic, liquid fuel, hydraulic, or powder-actuated.
  • Lower or block the blades of bulldozers, scrapers, and similar equipment before you make repairs or when the equipment is not in use.
  • Use lockout/tagout procedures for machinery and equipment used in concrete and masonry operations.

2. To protect against caught-in between hazards, workers should _____.

a. not wear loose clothing or jewelry
b. use pull-back straps and other PPE
c. remove gloves and hair nets
d. disconnect tools while in use

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Pinned-Between or Crushed-by Hazards

The employer must take measures to prevent workers from being pinned between equipment and a solid object, such as a wall or another piece of equipment; between materials being stacked or stored and a solid object, between shoring and construction materials in a trench.

The best way to prevent workers from being pinned or crushed by heavy equipment that tips over is to prevent the equipment from tipping over in the first place. For example, cranes can tip over if the load capacity is exceeded, or the ground is not level or too soft.

  • The employer must designate a competent person to inspect crane operations to identify hazardous working conditions, including ensuring the support surface is firm and able to support the load.
  • The employer must also make sure the material handling equipment is equipped with rollover protective structures.
  • Motor vehicles, forklifts, and earthmoving equipment must be equipped with seat belts and use is required.

3. The best way to prevent workers from being pinned or crushed by heavy equipment that tips over is to _____.

a. install outriggers when digging trenches
b. prevent the equipment from tipping over in the first place
c. designate a worker to monitor equipment stability
d. lower tire pressure to increase stability

Next Section

Collapsing walls are a serious hazard that can easily crush a worker.

Pinned-Between or Crushed-by Hazards (Continued)

Workers may be pinned or crushed by equipment, machinery, or structures if parts break, power is lost, or structures become unstable. For instance, a crane boom, scaffold, trench plates, or a wall might unexpectedly collapse.

During demolition, your employer must ensure any stand-alone walls more than one story must have lateral bracing unless the wall was designed to be stand-alone and is otherwise in a safe condition to be self-supporting.

  • Jacks must have a firm foundation. If necessary, the base of a jack must be blocked or cribbed. After a load has been raised, it must be cribbed, blocked, or otherwise secured at once.
  • When balling or clamming is being performed, only the personnelnecessary for the work must be allowed in the work area.
  • Your employer must make sure that proper bracing is used between heavy plates used as shoring in a trench.
  • The employer must carefully arrange the path of travel when loading/unloading, stacking, and storing materials so that no workers will be caught between materials and moving equipment or between materials and a wall.

Click on the button below to see what additional measures to take to protect yourself from being pinned between or crushed by equipment, objects, or materials.

  • be aware at all times of the equipment around you and stay a safe distance from it;
  • never place yourself between moving materials and an immovable structure, vehicle, or stacked materials;
  • make sure all loads carried by equipment are stable and secured;
  • never walk or work under a load that is suspended;
  • stay out of the swing radius of cranes and other equipment; and
  • wear a seat belt, if required, to avoid being thrown from a vehicle and then potentially being crushed by the vehicle if it tips over.

Click on the button below to review a pinned-between accident.

Description of the accident

The son of the owner of a commercial drywall construction company, an employee of the company, was preparing an aerial lift for a job and had replaced two battery terminals. He had raised the aerial boom and was reaching toward the battery compartment across the metal enclosure that houses the lift's toggle controls when the boom dropped and pinned him to the control panel. His father discovered him and summoned emergency responders, but he died at the site.

Investigation Findings

  1. The lift's emergency valve, hydraulic hoses and fittings, and electrical wiring were inspected after the accident and were not defective; however, the on/off key switch had been bypassed so that the operator could use the toggle switches without using the key.
  2. The battery charging system was missing a fuse that would stop the system from charging, and the spring-loaded toggle switches that controlled the boom did not have guards to prevent accidental contact.
  3. The employee did not use lockout procedures while he was working on the lift and did not block the boom to prevent it from dropping.
  4. The owner had not reviewed the lift's instruction manual with the victim or other company employees.
  5. Although the company had more than 10 employees, it did not have a safety committee.

The accident resulted in the OSHA violations listed below:

  1. The employer failed to ensure that employees did not remove or tamper with required safety devices.
  2. The employer did not develop, document, and require employees to use lockout procedures to control hazardous energy during maintenance work.
  3. The employer had more than 10 employees but did not have a safety committee.(State of Oregon requirement)

4. During demolition, your employer must ensure non-designed stand-alone walls over one story _____.

a. are surrounded by warning lines
b. display warning signs
c. are equipped with jacks
d. have lateral bracing

Next Section

Excavation Sites

A competent person must inspect each trench.

You must be protected from equipment or materials that could fall or roll into excavations. This could include spoils that could fall into the trench and bury the workers. A warning system must be used (such as barricades, hand or mechanical signals, or stop logs), when mobile equipment is:

  • operated next to an excavation or
  • is required to approach the edge of an excavation, and
  • the operator does not have a clear and direct view of the edge of the excavation. If possible, the grade should be away from the excavation.

OSHA standards require, before any worker entry, that employers have a competent person inspect trenches daily and as conditions change to ensure elimination of excavation hazards.

Do's and Don'ts

Click on the buttons below to see some important do's and don'ts while working in or around trenches and excavations.

  • enter or exit a trench or excavation using a ladder, stairway or properly designed ramp that is placed within the protected area of the trench
  • keep heavy equipment away from trench edges.
  • identify other sources that might affect trench stability.
  • keep excavated soil (spoils) and other materials at least 2 feet (0.6 meters) from trench edges.
  • know where underground utilities are located before digging.
  • test for atmospheric hazards such as low oxygen, hazardous fumes and toxic gases when greater than 4 feet deep.
  • inspect trenches at the start of each shift.
  • inspect trenches following a rainstorm or other water intrusion.
  • inspect trenches after any occurrence that could have changed conditions in the trench.
  • ensure workers wear high visibility or other suitable clothing when exposed to vehicle traffic.

  • work in a trench if a crane or earthmoving equipment is operating directly over the top of the trench;
  • work under suspended or raised loads and materials.
  • work in an unprotected trench five feet deep or more;
  • work outside of the confines of the protection system.

Click on the button below to view a video detailing an actual accident


5. Which of the following is required if mobile equipment is used near or over an excavation?

a. Horizontal bracing for plates
b. Hard hats for workers in the trench
c. A competent observer
d. A suitable warning system

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Excavation Sites (Continued)

The type of protection working in trenches 5-20 feet deep may be one of the following:

  • Sloping or benching: Sloping is cutting back the sides of the trench to a safe angle so it won't collapse. Benching uses a series of steps that approximate the safe sloping angle. The angle depends on the soil type.
  • Trench box or shield: These do not prevent cave-ins but protect the workers who are in them if a cave-in happens.
  • Shoring: Shoring are wooden structures or mechanical or hydraulic systems that support the sides of an excavation.
Image of sloping


All simple slope excavations 20 feet (6.11 meters) or less deep should have a maximum allowable slope of 1-1/2:1. A slope of this gradation or less is safe for any type of soil.

Types of shoring

Your employer must make sure all excavations and trenches five feet deep or more, but less than 20 feet, are protected by sloping or benching, trench box or shield, or shoring. There must also be an adequate means of access and egress from the excavation. If an excavation is more than 20 feet deep, a professional engineer must design the system to protect the workers.

6. Which of the following protection measures is required for excavations more than 20 feet in depth?

a. Engineered system
b. Trench box
c. Shoring
d. Sloping

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Buried-by Structures and Materials

Measures need to be taken by your employer to avoid the collapse of other structures, such as scaffolds, that could bury workers underneath them.

There is a danger of collapse anytime there is inadequate support, improper construction, or a shift in the components of a scaffold (including the base upon which the structure is built). For instance, cinder blocks or other similar materials should not be used to support a scaffold because they could be crushed. To support scaffolds, use only suitable base plates on wood sills.

OSHA standards require that scaffolds can only be erected, moved, dismantled or altered under the supervision of a competent person.

  • The competent person selects and directs the workers who erect the scaffold.
  • The selected workers must be trained by a competent person on correct procedures and hazards of scaffold erection.

7. Which of the following is suitable for supporting scaffolds so they won't collapse?

a. Base plates
b. Cinder blocks
c. Equipment
d. Barrels

Next Section

Designate a Competent Person

OSHA defines a "competent person" as:

"one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them."

Your employer must designate a competent person for certain construction activities that may have caught-in between hazards:

  • training for scaffold erection
  • inspections of excavations, the adjacent areas, and protective systems
  • engineering survey prior to demolition of a structure (and any adjacent structure where workers may be exposed) to determine the condition of the framing, floors, and walls, and possibility of unplanned collapse
  • continuing inspections during demolition to detect hazards resulting from weakened or deteriorated floors, or walls, or loosened material

8. Who must train, inspect, and survey safe conditions on most construction sites?

a. A designated manager
b. An experienced operator
c. A safety supervisor
d. A competent person

Next Section


Make sure you have the proper training on the equipment and hazards of your job so you can work safely. Specific and detailed training is a crucial part of any effort to safeguard employees from worksite hazards.

OSHA’s general training requirement for construction workers is:

The employer shall instruct each employee in the recognition and avoidance of unsafe conditions and the regulations applicable to his work environment to control or eliminate any hazards or other exposure to illness or injury. One way to do this is to review and discuss OSHA Accident Facts.

Your employer must train you to perform your job and use the provided equipment safely. If working with scaffolding your employer should be aware of specific training requirements found in OSHA standards. These standards can be found in 29 CFR 1926.454 (Scaffolds – workers who are involved in erecting, disassembling, moving, operating, repairing, maintaining, or inspecting a scaffold).

9. Providing worker training on the safe use of the equipment being operated is the responsibility of _____.

a. the lead contractor
b. an experienced safety professional
d. the employer

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.

Final Exam