Chapter 9

Reading Hazardous Energy

Objectives

• Define hazardous energy and list four ways to categorize its status

• List common electrical equipment and their associated hazards

• List the chemical properties of common utility gases

• List the hazards associated with utility water and storm sewer systems

Objectives (con’t.)• Give examples of mechanical hazardous

energy• List the hazardous energy sources in

vehicles• Discuss weather as hazardous energy and

itemize the warning signs that extreme weather is approaching

• Describe why water is a form of hazardous energy

Defining Hazardous Energy

• Hazardous energy– Stored potential energy that causes harm if

suddenly released

• ISO functions– Predict release– Analyze energy form and determine degree of

impact

Defining Hazardous Energy (con’t.)

• ISO functions (con’t.)– Categorize the status of hazardous energy form

• Stable – not likely to change• Stable – may change• Unstable – may require attention• Unstable – requires immediate attention

– Intervene appropriately

Figure 9-1 The ISO should be comfortable with electrical terms and be able to communicate hazards accurately.

Forms of Hazardous Energy

Forms of Hazardous Energy (con’t.)

• Electricity– Integrity of systems based on proper

grounding, insulation, and circuit protection– Local power company usually assists

firefighters at incidents– ISO must understand electrical systems

• Take no-cost seminars and workshops at local power company

Figure 9-2 ISOs must be able to recognize the components of a typical municipal grid.

Figure 9-3 Electrical components can present hazards to firefighters.

Figure 9-4 This typical power pole arrangement is just one of the many possible.

Forms of Hazardous Energy (con’t.)

• Electricity (con’t.)– Seeks path of least resistance to ground– Ground gradient

• Electrical energy that has established a path to the ground through the earth and continues to energize the earth

• Example: downed power line can energize the earth in a concentric ring of up to 30 feet

Table 9-1 Minimum distance requirements when working around electrical equipment.

Forms of Hazardous Energy (con’t.)

• Electricity (con’t.)– ISOs should evaluate the proximity and

integrity of electrical systems – Exercise particular caution in:

• Battery rooms: energized DC, wet batteries• Substation fires: transformer oil, pooled water, “reel

coil”

Forms of Hazardous Energy (con’t.)

• Utility gas– Evaluate integrity of gas fuel supply and

containment vessel– Excess pressure in components can cause

pressure relief device to release expanding gas– Trauma can cause holes, pipe separation, or

container failure– Escaped gas can accelerate fire, release

toxins, and present explosion hazard

Figure 9-5 The ISO who knows gas properties can more effectively assess risks associated with utilities.

Forms of Hazardous Energy (con’t.)

• Utility water and storm sewer systems– Uncontrolled water flow can cause initial and

secondary collapse in structures– Damaged drain system can leak and

undermine ground support– Pooled water in structures can extinguish pilot

lights and release raw gas into water– Flash floods cause localize flooding and may

trap victims into debris and grates

Forms of Hazardous Energy (con’t.)

• Mechanical energy– Includes pulleys, cables, counterweights, and

springs– Sudden release of mechanical systems can be

caused by heat, trauma, and /or overloading• Steel cable and “guy” wires can recoil with amazing

force

– Freestanding truss structures are weakened quickly when exposed to heat

• Horizontal forces can accelerate collapse

Forms of Hazardous Energy (con’t.)

• Pressurized systems and vessels– Use hydraulics or pneumatics as a medium– Heat may increase pressure beyond design

limits– Pressure relief system failure may result in

component explosion• Component may act as a missile• The stronger the component, the more explosive it

becomes when it fails

Forms of Hazardous Energy (con’t.)

• Hazardous energy in vehicles– Stability/position

• Rolling weight, instability, collapse, ground support failure

– Fuel systems• Fuel types, storage, pumps, fuel lines, pressurization

– Electrical systems• Batteries, converters, high-voltage wires

Forms of Hazardous Energy (con’t.)

• Hazardous energy in vehicles (con’t.)– Power generation systems

• Pulleys, belts, heat, noise, thrust, exhaust gases

– Suspension/door systems• Springs, shocks, gas or pneumatic struts

– Drive/brake systems• Pressure vessels, heat, springs, torsion, exotic metal

fumes

Forms of Hazardous Energy (con’t.)

• Hazardous energy in vehicles (con’t.)– Restraint safety systems (air bags)

• Trigger systems, chemicals• Delayed or unpredicted deployment can cause injury

to rescuers (c-spine trauma, muscle sprain, contusions, and lacerations)

– Alternative fuels and fuel systems have few standards and may resist fire control measures

– High-voltage systems have large battery packs

Forms of Hazardous Energy (con’t.)

• Weather– Effective ISOs

• Study weather and understand weather patterns in their geographical regions

• Keep abreast of daily forecasts of weather observations as a matter of habit

Forms of Hazardous Energy (con’t.)

• Weather (con’t.)– Wind

• Most important consideration• Strong or changing winds can affect firefighting

operations in outside or structural fires

– Humidity• Lower humidity means increased fire speed• High humidity affects firefighter health and smoke

dissipation

Forms of Hazardous Energy (con’t.)

• Weather (con’t.)– Temperature

• Evaluate relative to its effect on firefighter exposure• Acclimation is key!

– Potential for change/storms• Watch the sky• Note 180-degree changes in wind direction for a

short period of time• Be mindful of the potential for a flash flood

Forms of Hazardous Energy (con’t.)

• Weather (con’t.)– Potential for change/storms (con’t.)

• Developing thunderstorms can produce rapid changes

• At night, use lightning flashes to define cloud formations that may be tornadic

• Calculate lightning distance: seconds between lightning flash and thunder divided by five

• Deep snow makes travel difficult and can hide hazards

Figure 9-6 Erratic wind shifts are common during thunderstorms. The ISO needs to watch weather influences during incidents.

Forms of Hazardous Energy (con’t.)

• Miscellaneous hazard energy forms– Earthen materials– Ice– Flowing water– Animal movement

• Evacuation of penned, fire-threatened animals is amazingly dangerous

– High-tech medical devices• Example: MRI equipment

Summary

• Hazardous energy– Stored potential that can cause harm if

suddenly released

• ISOs functions at hazardous energy incidents – Identify hazardous energy forms– Categorize potential impact on firefighters

Summary (con’t.)

• Forms of hazardous energy– Electricity– Utility gases– Water and storm systems– Mechanical energy– Pressurized vessels– Vehicle components

Summary (con’t.)

• Forms of hazardous energy (con’t.)– Weather

• Wind • Temperature• Humidity• Potential for storms and rapid change

– Animals