UFC 3-560-01
6 December 2006
Including change 1, 7 December 2006
1-7.2
Danger from Arcs and Blasts. This UFC addresses arc flash criteria for
electrical safety. Arcs result from the passage of electric current through air; the air
failing as an insulator but serving as a conducting medium for ionized gases. Blasts
result when the metal at the arc site expands and vaporizes. Arcs can reach
temperatures up to four times the temperature of the sun's surface. Water expands
1,670 times when it becomes steam; copper expands 67,000 times when it vaporizes.
High energy arcs can be fatal even at distances of 10 ft (3 m).
1-7.3
Workplace Dangers. Table 1-2 indicates typical hazardous materials that
can be found in enclosures or confined work spaces. Check the applicable material
safety data sheets (MSDS).
Table 1-2. Hazardous Materials
Material
Source
Asbestos*
Insulation, underground manholes, under houses;
crawl spaces, old electric equipment, fire protecting
tape, duct banks, arc chutes/shields, cables, and
wiring
Polychlorinated biphenyl (PCB)
Old liquid-filled transformers, capacitors, ballasts,
lead-sheathed cables
Sulfur hexafluoride (SF6)
Toxic decomposition products from electric arcs or
faults acting on SF6 insulation
Combustible gases
Sewer or natural gas accumulations or from
outgassing of lead-acid batteries
Carbon monoxide
Cable faults, combustion engine exhausts
Hydrogen chloride
Faults or fires involving polyvinyl chloride (PVC)
conduits or PCB oils
Inadequate oxygen
Displaced by heavier-than-air gases
Note: Asbestos was a widely used insulator. If insulation is not marked as being
"Asbestos Free", consider it to contain Asbestos. Avoid disturbing the material, getting
it on clothing, or any activity that could make the fiber airborne.
1-7.4
Health Hazards of Asbestos. Asbestos is a known human carcinogen. Its
primary route of entry to the body is by inhalation, however exposure can occur by
ingestion. Asbestos is not absorbed through the skin. The diseases caused by long
term exposure to asbestos are: cancer of the lungs, pleura sack surrounding the lungs,
bronchus, oropharynx, stomach, and colon. Symptoms are shortness of breath, dry
cough, and clubbing of the fingers. These symptoms generally do not show up for 20
years or more after initial exposure. The potential for a material containing asbestos to
1-7
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