Driving, Hazards, & Risk Assessments

Before diving into the risk associated with energy sources and sources of harm, let’s get a quick reminder of what is a hazard and what is risk.

hazard is any source of potential damage, harm or adverse health effects on something or someone under certain conditions at work.  So, a hazardous energy is any electrical, mechanical, pneumatic, chemical, nuclear, thermal, gravitational, or other energy that can harm people.  Some energy sources are obvious, such as electricity, heat in a furnace, or an object that might fall.  Others may be hidden hazards such as air pressure in a tank or a compressed spring.


Risk is the chance or probability that a person will be harmed or experience an adverse health effect if exposed to a hazard. It may also apply to situations with property or equipment loss.

Depending on your client, the definition of risk may vary, but in general, risk is defined as a measure of loss, harm to people, the environment, compliance status, reputation, and assets or business performance.

Factors that influence the degree of risk include:

  • How much a person is exposed to a hazardous energy;
  • How the person is exposed (e.g., breathing in a vapor, skin contact);
  • How severe are the effects under the conditions of exposure.

Hazardous Energy Sources:

Electrical energy is the most common form of energy used in workplaces.  It can be available live through power lines or it can also be stored (e.g., batteries or capacitors).  Electricity can harm people in one of three ways: shock, secondary injury, or exposure to an electrical arc or flash.

Hydraulic potential energy is the energy stored within a pressurized liquid.  When under pressure, the fluid can be used to move heavy objects, machinery, or equipment.  Examples include: automotive car lifts, articulations of heavy equipment, pressure washers, power presses, and the braking system in cars.  When hydraulic energy is released in an uncontrolled manner, individuals may be crushed or struck by moving machinery, equipment or other items.

Pneumatic potential energy is the energy stored within pressurized air.  Like hydraulic energy, when under pressure, air can be used to move heavy objects and power equipment.  Examples include spraying devices, air compressor tanks, or machinery.  When pneumatic energy is released in an uncontrolled manner, individuals may be crushed or struck by moving machinery, equipment or other items. Example: a one foot square port on a tank pressurized to 2 psi carries the potential force of almost 300 pounds.

Chemical energy is the energy released when a substance undergoes a chemical reaction.  The energy is normally released as heat, but could be released in other forms, such as pressure.  A common result of a hazardous chemical reaction is fire or explosion.

Radiation energy is energy from electromagnetic sources.  This energy covers all radiation from visible light, lasers, microwave, infra-red, ultraviolet, and X-rays.  Radiation energy can cause health effects ranging from skin and eye damage (lasers and UV light) to cancer (X-rays).

Gravitational potential energy is the energy related to the mass of an object and its distance from the earth (or ground).  The heavier an object is, and the further it is from the ground, the greater its gravitational potential energy.

Mechanical energy is the energy contained in an item under tension.  For instance, a spring that is compressed or coiled will have stored energy which will be released in the form of movement when the spring expands.  The release of mechanical energy may result in an individual being crushed or struck by the object.


It is important to understand that all of these energy types can be considered as either the primary energy source, or as residual or stored energy (energy that can reside or remain in the system).  Primary energy source is the supply of power that is used to perform work.  Residual or stored energy is energy within the system that is not being used, but when released it can cause work to be done.

For example: when you close a valve on a pneumatic (air) or hydraulic (liquid) powered system, you have isolated the system from its primary energy source.  However, there is still residual energy stored in any air or liquid that remains in the system. In this example, removing the residual energy would include bleeding out the liquid, or venting out the air.  Until this residual energy is removed from the system, “work” can occur, whether on purpose or inadvertently.

Not properly assessing and dissipating stored energy is one of the most common causes for workplace incidents that involve hazardous energy.  As a refresh, visit the Stratus Hierarchy of Control Measures (Eliminate the hazard, Substitute the hazard with a lesser risk, Use engineering controls, Isolate the hazard, Use administrative controls, and Use personal protective equipment) on methods to remove a hazard, reduce the potential exposure to the hazard or reduce the likelihood of the risk of the exposure to that hazard.

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