ACCIDENTAL FIRES

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ACCIDENTAL FIRES
Fire/Arson investigators should be able to
accurately determine the cause of all types of
fires to which they are called. The investigator
must know and understand those accidental fire
causes which are found in various
occupancies. Criminal prosecutions of arson
depends on the ability of the investigator to
prove the fact of incendiarism and the fact of
non-accidental fire cause. The cause of a fire
MUST BE DETERMINED before corrective action can
be taken.
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I. Basic Fire Elements
Three elements, or factors, must be present to
initiate a fire.

• A. Heat Sources (4)
• 1. Chemical
• a. Heat of Combustion (burning)
• b. Spontaneous heating
• c. Heat of decomposition
• d. Heat of solution Heat released when a
  substance is dissolved

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Basic Fire Elements

• 2. Electrical
• a. Resistive heating
• b. Induction heating
• c. Dielectric heating, ie. dust or dirt
  collecting on an insulator allowing a fault or
  leak of electrical current
• d. Heat from electric arcing (includes static
  electricity
• e. Heat generated by lightning

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Basic Fire Elements

• 3. Mechanical
• a. Friction heat
• b. Friction sparks
• c. Overheating of machinery (may be considered a
  form of friction heat

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Basic Fire Elements

• 4. Nuclear Heat
• a. Fission - splitting of atoms
• b. Fusion - splitting of atoms

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Basic Fire Elements

• B. Fuel The ease of ignition depends on
• 1. Mass of the Fuel
• 2. State of the Fuel
• a. Solid
• b. Liquid
• (1) Ambient temperature
• (2) Flash point
• c. Gas or vapor

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Basic Fire Elements

• C. An event which brings together the heat
  source and the fuel may be
• 1. An action
• or
• 2. Lack of an action

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II. Fire Causes and Reasons

• A. Accidental (including natural)
• 1. Fires resulting from actions or inactions
• a. Fires caused by carelessness
• b. Providential acts or Acts of God
• 2. Any fire incident NOT resulting from intent or
  design
• B. Incendiary
• 1. Any fire caused intentionally
• 2. Any fire allowed to start intentionally

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Fire Causes and Reasons

• C. Other classifications generally refer to the
  status of the investigation or a reason for the
  cause itself. Suspicious, not investigated,
  undetermined, and under investigation designate
  the investigative status.

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Fire Causes and Reasons

• D. Major Accidental Fire Causes
• 1. Spontaneous heating
• 2. Low temperature ignition, careless use of
  smoking materials
• 3. Open flames and sparks, burning trash
• 4. Heating equipment
• 5. Cooking equipment
• 6. Energized electrical equipment
• 7. Gas fires and explosions
• 8. Dust explosions
• 9. Flammable and combustible liquids
• 10. Others lightning, fireworks, explosives

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III. Spontaneous Heating

• A. Although probably somewhat rare except in
  rural areas, spontaneous heating is sometimes
  used as a catch-all by investigators faced with
  having to list a fire cause and being unable to
  find a correct cause.
• B. Many organic materials and some metals are
  subject to oxidation and/or fermentation which
  results in spontaneous heating.

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Spontaneous Heating

• C. Spontaneous heating is produced in three ways
• 1. Chemical Action
• a. Unmined coal igniting underground
• b. Unslaked lime in contact with water
• Slake to cause (as lime) to heat and crumble by
  treatment with water, hydrate (Websters)
• c. Other hazardous substances in contact with
  water, ie. metallic sodium, potassium, sodium
  hydroxide, and calcium oxide

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Spontaneous Heating

• 2. Oxidation
• a. Most often associated with vegetable oils or
  materials containing vegetable oils and
  by-products
• b. Examples oil mops, oily rags, paint rags and
  brushes
• c. May require hours or days to build up enough
  heat to ignite
• Spontaneous heating due to oxidation most often
  occurs in unsaturated hydrocarbon compounds

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Spontaneous Heating

• 3. Fermentation
• a. Most common type of spontaneous heating
• b. Occurs in vegetable matter such as hay, grain,
  straw and manure
• (1) Low moisture content will not ferment
• (2) High moisture content will not ignite

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Spontaneous Heating

• d. Spontaneous heating may be accelerated by
  outside heat sources
• (1) Sunshine
• (2) Storage near steam pipes or heaters
• (3) Hot air ducts
• (4) Friction

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Spontaneous Heating

• e. Available air is important to spontaneous
  heating
• (1) Too much air may dissipate the heat
• (2) Too little air may retard heating
• (3) Example Oily rags in the bottom of a trash
  can may produce heating, but the same rags spread
  out on the floor may simply dry out

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Spontaneous Heating

• f. Material mass is important. Usually, several
  inches of depth is required to allow spontaneous
  heat to build up.
• g. Spontaneous heating may occur for hours, days,
  or even months, prior to reaching ignition
  temperature.
• h. Bacteriological preheating (Microbial
  Thermogenesis) MAY initiate the fermentation
  process causing spontaneous heating with
  oxidation occurring in the later stages just
  prior to ignition.

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Spontaneous Heating

• i. Some common materials subject to spontaneous
  heating

(1) Alfalfa meal (2) Charcoal (3) Colors in
oil (4) Cod liver oil (5) Fish meal (6) Fish
oil (7) Fish scrap
(8) Linseed oil (9) Red skin peanuts (10) Tung
nut meals (11) Varnished fabrics (12) Certain
metals in fine powder form, shavings, chips or
turnings
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Spontaneous Heating

• j. Charring inside the mass, or charring of more
  than one area inside the mass, is an indicator of
  fire caused by spontaneous heating
• Hay clinker
• Clinker stony matter fused together SLAG
  (Websters)
• Kirks Fire Investigation gives a good
  explanation of spontaneous heating

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IV. Low Temperature Ignitionand Careless use
ofsmoking materials

• When temperatures as low as 250 F. is applied to
  cellulosic materials, such as wood, cotton and
  other organic compounds, for an extended period
  of time, a chemical change occurs known as
  PYROLYSIS.
• A. Pyrophoric carbon is formed
• 1. The character of the material is changed
• 2. Exposed material becomes almost pure carbon
  and is subject to spontaneous heating

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Low Temperature Ignition

• B. Low temperature ignition may occur in areas
  where combustible materials are located near
  light bulbs, steam pipes, electric irons, or
  other low temperature heat generating equipment.
• C. Small or thin materials may not be effected
  due to their low mass or low density
• 1. Pyrolysis usually occurs in heavier timbers
• 2. The density of a material has an insulating
  effect.

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Low Temperature Ignition

• D. Low temperature heating may occur over an
  extended time period, from several weeks to
  several years
• E. Common sources of low temperature heat,
  sufficient to cause pyrolytic decomposition are
• 1. Electric light bulbs generating surface heat
  from around 200 F. to near 400 F.
• 2. Steam pipes generating surface heat between
  240 F. and 260 F.

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Low Temperature Ignition

• F. Indicators of low temperature ignition
• 1. Large, charred section of combustible material
• 2. Presence of low temperature heat source
• 3. A discoloration or baking of the material

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Low Temperature Ignition

• G. Smoking Materials Related Fires
• 1. The temperature generated by burning
  cigarettes varies greatly, from
• a. About 550 F., measured on the outside surface
  of a glowing ash
• TO
• b. about 1350 F., measured near the center of a
  glowing ash

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Low Temperature Ignition

• 2. Cigarettes in contact with most combustibles
• a. usually cause local charring or damage due to
  a small contact area
• AND
• b. are often self-extinguishing
• 3. Careless use of smoking materials is often
  over-used by investigators thinking this cause
  will be difficult to contradict

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Low Temperature Ignition

• 4. Cigarettes and the ignition of combustibles
• a. Cigarettes usually must be insulated to ignite
  combustible materials
• (1) Allows build-up of heat
• (2) Increases surface contact
• b. An insulating effect occurs when cigarettes or
  burning ashes fall between cushions of sofas or
  chairs

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Low Temperature Ignition

• c. EXCEPTION A cigarette in open contact with
  cotton bed coverings, ie. sheets, mattress
  covers, etc.
• (1) The insulation affect may not be necessary
• (2) Mattress padding may begin smouldering
• 5. Smouldering furniture usually requires a long
  period of time to produce open burning from
  1-1/2 hours to several hours

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Low Temperature Ignition

• 6. Smouldering fires inside padded furniture may
  produce temperatures from 1400 to 1600 degrees F.
• 7. Indicators of fires in furniture caused by
  cigarettes
• a. Collapse of springs, which usually requires
  temperatures of about 1500 F. to cause loss of
  spring temper. (also known as annealing)
• b. Smouldering furniture fires usually produce
  large quantities of heavy smoke, resulting in
  heavy smoke stain on windows and mirrors in the
  area near the point of origin

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Low Temperature Ignition

• c. Heavy floor damage (charring) may result from
  smouldering furniture fires
• (1) May resemble flammable liquid pattern on the
  floor
• (2) May mislead investigators
• d. Almost total destruction of the involved
  article may result.

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Low Temperature Ignition

• 8. Exceptions to be considered when investigating
  fires thought to have started from contact of
  furniture with cigarettes
• a. Large quantities of flammable liquids on or
  under furniture can cause spring collapse
  (annealing)
• (1) Small quantities of flammable liquids usually
  cause only local damage
• (2) Small quantities usually cause top or surface
  burning

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Low Temperature Ignition

• b. Fires resulting in building collapse or
  extensive damage may produce sufficient heat to
  anneal (collapse) furniture springs
• 9. SOME, NOT ALL, foamed plastics, foam rubber,
  and/or polyfoam furniture padding
• a. may produce more heat than older (cotton
  padded) furniture
• b. may or may not ignite easily upon contact with
  a lighted cigarette, depending upon the chemical
  composition of the material

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Low Temperature Ignition

• c. May produce melted, napalm-like materials,
• (1) generating extreme heat
• (2) generating extreme smoke
• (3) causing very rapid burning
• (4) creating very deep char patterns

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Low Temperature Ignition

• 10. Cigarettes in contact with flammable gases or
  vapors
• a. The cold ash around a burning coal may act as
  a flash screen, similar to the screen in
  flammable liquid safety cans
• b. Explosions of flammable gases may occur when
  an individual attempts to light a cigarette using
  a match or a lighter
• c. Explosions CAN occur, and MUST NOT BE
  OVERLOOKED

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V. Open Flames and Sparks

• A. Sparks are hot and/or burning fragments
  emitting from at heat source.
• B. Sparks are not generally considered a primary
  source of ignition
• C. Sparks are commonly found to be bits of
  glowing or burning wood, paper, or other organic
  material.

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Open flames and Sparks

• D. Significant sources for sparks would be
• 1. Fireplaces and chimneys through
• a. Open fronts on fireplaces resulting in small
  spots on the floor and possibly igniting carpets,
  rugs and/or furniture
• b. Top of chimney resulting in fires on roofs or
  in other nearby flammable materials
• c. Chinks or defects in a chimney wall allowing
  ignition of supporting timbers and construction
  materials near or in contact with the chimney

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Open flames and Sparks

• 2. Incinerators and trash burners
• a. Usually rate high as a source of sparks and
  burning fragments
• b. Most are used to destroy materials likely to
  generate many sparks, ie, paper, trash
• c. Probably cause more grass fires than roof fires

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Open flames and Sparks

• 3. Bonfires and campfires
• a. Usually generate less high-flying embers and
  brands due to density of the material being
  burned, ie, wood
• b. Lack of restraint and protection from wind
  allows horizontal fire spread at ground level
• c. Very dangerous from the standpoint of igniting
  larger, uncontrolled fires in surrounding grass
  and leaves

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VI. Heating Equipment

• A. Heating equipment may become defective or
  overheat and become an ignition source.
• 1. May be installed too close to combustible
  materials. Should comply with manufacturers
  instructions or follow guidelines of NFPA
  Handbook
• 2. Combustibles may be placed too close to
  heating device, ie, clothes or papers

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Heating Equipment

• B. Oil burning equipment
• 1. Observe the firebox, pipes and flues, looking
  for excess soot which could indicate incomplete
  combustion due to malfunction or improper
  adjustment
• 2. The point of origin may be located near the
  pipes or flues

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Heating Equipment

• 3. Check the controls and fuel lines for
• a. Prior trouble with equipment indicated by
  fresh tool marks indicating attempted repairs
• b. Fuel leakage soaked into the floor

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Heating Equipment

• C. Gas burning equipment
• 1. Check firebox, pipes and flues as above
• 2. Check the controls and gas lines as above

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Heating Equipment

• D. Electrical heating equipment (portable)
• 1. Again, check for combustibles too close to the
  equipment
• 2. Check the units controls
• a. Main switch on or off
• b. Tilt or overturn switch in place or missing
• 3. Is the unit in its normal location?
• 4. Check for electrical short circuits
• E. Electrical heating equipment (stationary) same
  as portable except location and tilt switch.

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Heating Equipment

• F. Coal, wood, or other solid fuel heating
  systems
• 1. Often over supplied with fuel
• 2. Often causes fires in nearby combustibles
• 3. Fuel supplies often are stored too close to
  the heating unit. (includes combustible
  liquids/combustible starting fuels)
• 4. Check the combustion and flue areas
• 5. Check old solid fuel units to see if they
  have been converted to burn liquid fuels. If so,
  they may leak and/or overheat

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Heating Equipment

• G. Technical information on specific heating
  equipment may be found at dealerships, in owners
  manuals, or in the NFPA Handbook.

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VII. Cooking Equipment

• A. Consider your point of origin in respect to
  the location of the cooking equipment. Most
  severe burning will be directly above the
  equipment.
• B. Check the position of all controls and heating
  elements.

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Cooking Equipment

• C. Check the location of the rooms trash
  containers.
• 1. Often placed between the cooking equipment and
  a cabinet or wall
• 2. Ignition of the trash may occur due to
• a. Splattering grease
• b. Conducted heat from the equipment
• D. Check for an accumulation of trash behind the
  equipment.

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Cooking Equipment

• E. Observe all electrical contact points of the
  controls, switches, and thermostats, for
  malfunction. If the equipment is gas or oil
  fired, check all valves and fuel lines.
• F. Look for any signs of repair or adjustments to
  fuel or electrical supply
• 1. Tool marks
• 2. Missing cover plates or screws

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Cooking Equipment

• G. Be aware of attempts by occupants to remove
  burning fuel from the equipment
• 1. Burning pans may be dropped or thrown,
  resulting in burn injuries to occupants.
• 2. The point of origin may appear to be located
  at floor level.
• 3. The point of origin may appear to be located
  in or near the sink.
• 4. The floor may appear to have been spread with
  a flammable accelerant.

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Cooking Equipment

• H. Check time factors
• 1. Did the fire occur during normal meal
  preparation time?
• 2. Check for other evidence of meal preparation
• 3. Check the number of heating elements being
  used
• I. Commercial cooking equipment is generally
  equipped with automatic power shut-offs and
  extinguishing systems which should operate when
  excessive heat is incurred.

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VIII. Energized Electrical Equipment and
ElementaryElectrical Theory

• A. Home and commercial electrical protection
  devices
• 1. Designs are based on the National Electrical
  Code, a publication of the National Fire
  Protection Association.

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Electrical Equipment

• 2. Incoming electrical power is usually protected
  by a fuse or circuit breaker at the meter
  connection on or near the structure being
  serviced.
• a. The fuse or breaker should be rated to
  correspond to the power (current) demands of the
  structure, generally 60 amps or more depending on
  the type occupancy.

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Electrical Equipment

• b. For residential service, incoming power may be
  from 110 volts to 120 volts for small appliances,
  lights, etc. 220 volts to 240 may also be
  provided to residential occupancies for use with
  heavy appliances, window air conditioning units,
  central air and heating units, ranges, ovens,
  etc.
• c. Commercial and industrial occupancies often
  require 440 volt service or greater.

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Electrical Equipment

• 3. Electric power service normally enters the
  structure at a distribution panel containing
  overcurrent protective devices, ie. fuses or
  breakers.
• a. The incoming main power is divided into
  secondary circuits such as
• (1) Lighting circuits
• (2) Appliance circuits
• (3) Water heater circuits (usually and individual
  circuit)

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Electrical Equipment

• (4) Range circuits (usually an individual
  circuit)
• (5) Heating/air conditioning (usually an
  individual circuit)
• b. Secondary circuits are normally called branch
  circuits, and extend beyond the overcurrent
  protective devices.

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Electrical Equipment

• c. Wiring found in branch circuits
• (1) General purpose and small appliance circuits
  are normally 12 guage (AWG- American Wire Gauge)
  and carry approximately 20 amps
• (2) Small appliance circuits found in kitchens,
  bathrooms, and residential garages should also be
  protected by a special type circuit breaker, a
  GFI (Ground Fault Interrupter).

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Electrical Equipment

• (3) Special purpose, individual branch circuits,
  provide service for individual appliances and
  utilize wire sizes and overcurrent protection as
  required by specific codes.
• 4. Grounding of circuits
• a. All metal appliance enclosures, metal
  conduits, and metal electrical conductors, should
  be connected to ground.

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Electrical Equipment

• b. Circuits shall be grounded through at least an
  iron or steel rod electrode. The rod shall be at
  least 5/8 inch in diameter and shall be installed
  so that at least 8 feet of the rod length is in
  contact with the soil. The rod shall be driven
  into the soil to a depth of eight feet, except
  that when a rock bottom is encountered, the rod
  shall be driven at an oblique angle not to exceed
  45 degrees from vertical or shall be buried in a
  trench at least 2-1/2 feet deep. 1993 NEC
  250-83(c)

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Electrical Equipment

• c. Loose connections or accidental overcurrents
  may energize appliances or other objects and
  cause shock and/or fire hazards.

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Electrical Equipment

• 5. Overcurrent Protection
• a. Current generates heat
• b. Excessive current due to an increased power
  demand, generates excessive heat, at times
  creating short circuits, which develop when two
  elements of different potentials come in contact
  with one another.

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Electrical Equipment

• (1) Ground fault is the most common type short
  and occurs when a hot wire contacts a ground or
  grounded wire. This produces a very large surge
  of current.
• (2) True short circuits occur when a hot wire
  contacts a neutral wire.

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Electrical Equipment

• c. If properly designed and operating, excess
  heat or a current surge should cause the
  overcurrent device to open or trip, stopping the
  current flow.

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Electrical Equipment

• 6. Typical overcurrent protective devices
• a. Fuses
• (1) Fuse links melt and produce an open circuit
• (2) Types of fuses
• (a) Edison - screw base glass or screw base
  creamic with glass windows. Up to 30 amps
  maximum. 15 amps or less have hexagonal windows.
  Above 15 amps have round windows.

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Electrical Equipment

• (b) S Type - similar to Edison, with the size
  of the screw base varying according to the amp
  rating.
• (c) Ferrule - clip in, cartridge type, resembling
  a shotgun shell. Cardboard with metal caps on
  either end. Rated up to 60 amps.
• (d) Blade - a cartridge fuse resembling a ferrule
  fuse except the endcaps have blades which fit
  into a clip in the panel. Rated 60 amps or above.

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Electrical Equipment

• (e) Time Delay - similar to an Edison fuse in
  appearance but designed to withstand momentary
  overloads without tripping. Sometimes called
  slow blow fuses. Time delay fuses are also
  available in cartridge type fuses.

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Electrical Equipment

• b. Circuit breakers
• (1) Circuit breakers are designed to open and
  close a circuit by non- automatic means and to
  open a circuit automatically at a predetermined
  overcurrent.
• (2) Older types usually contain bimetallic strips
  which heat and bend, opening contacts or tripping
  the breaker.
• (3) Newer types operate due to an increase or
  decrease in an electromagnetic field caused by
  current flow variations.

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Electrical Equipment

• B. Evaluating electricity as an accidental fire
  cause.
• 1. Conductor material (wires) for general wiring
  shall be of aluminum, copper-clad aluminum, or
  copper, and shall be insulated unless otherwise
  specified or specifically permitted by code.
  1993 NEC, 310-2

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Electrical Equipment

• 2. Aluminum wiring first came into use about
  1956.
• a. Contracts and expands approx. 38 more than
  copper.
• b. Oxidizes more than copper.
• c. Oxidation and expansion at connections may
  cause connectors to become loose.
• d. Aluminum and copper react with one another
  (electrolysis) and the connection may corrode due
  to the reaction.

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Electrical Equipment

• e. Proper connections MUST be used for copper to
  aluminum connections. Proper connectors will be
  marked as follows
• (1) AL/CU (aluminum/copper)
• (2) Connector may be painted white

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Electrical Equipment

• 3. Examine the service/distribution area,
  checking
• a. Fuses - Overheating usually causes little or
  no burning or discoloration. Electrical shorts
  usually cause sudden current surges resulting in
  discoloration.
• b. Circuit Breakers - May have been taped in an
  on position or be held in on position by a
  broom or mop handle.

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Electrical Equipment

• c. The distribution panel may show evidence of
  tool marks on the cover plate or have the cover
  plate removed.
• d. Check the panel for
• (1) Tight/loose connections
• (2) Pennies in fuse sockets
• (3) Altered fuses
• (4) Foil wrapped fuses
• (5) Solid metal jumpers
• (6) Jumper cables
• (7) Other bridging methods

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Electrical Equipment

• 4. Examine the undamaged building areas,
  evaluating the electrical system for
• a. Unsound mechanical work, missing cover
  plates, loose connections, splices, etc.
• b. Adequate number and placement of receptacles
• c. Evidence of circuit misuse such as many
  extension cords in use, extra long extension
  cords (longer than 8 feet), multi-adapters, etc.

73
Electrical Equipment

• d. Major appliances on light circuits
• e. NOTE Evidence of misuse or overuse of
  circuits DOES NOT PROVE an electrical fire cause,
  but DOES indicate a need for additional
  investigation.

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Electrical Equipment

• 5. Examine wiring in the area of the point of
  origin
• a. Aluminum wiring usually melts at about 1200
  degrees F. It may melt and run after causing a
  fire or may melt due to normal house fire
  temperatures.
• b. Copper wiring usually melts at about 2000
  degrees F, a temperature not normally produced in
  most structural fires of accidental cause.

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Electrical Equipment

• c. Heat damaged copper wire usually results in
  sharp pointed ends and some blistering may occur
  on the wire surface. Heat may also cause the
  wire to neck or have thin diameters resembling
  pulled taffy.
• d. Insulation may remain on heat damaged wire and
  may be tightly bonded to the wire due to external
  heat burning the insulation from the outside.

76
Electrical Equipment

• e. Sparks from electrical short circuits
  generate temperatures of from 2,000 to 7,000
  degrees F, and may cause damage to copper wiring.
• (1) Copper may melt and spatter
• (2) Beads may form at the ends of smaller wires
  or cable strands
• (3) Cavities may form on ends of larger cables

77
Electrical Equipment

• f. Insulation may indicate the type of heat
  present.
• (1) Internal head causes insulation to expand and
  produce a sleeve over the wire.
• (2) External heat may cause insulation to bond
  tightly to the wire.
• g. Short circuits may develop during the fire and
  do not, of themselves, indicate or prove the
  short to be the fire cause.

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Electrical Equipment

• h. Conduit or flexible metal cable (B cable) (BX
  Cable??) may develop cavities or blow outs from
  short circuits occurring during the fire.
• i. Evidence of short circuits very close to the
  point of origin indicate the need for additional
  investigation.

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Electrical Equipment

• j. Evaluate circuits containing suspected
  electrical fire causes, tracing wiring back to
  the distribution panel, checking for loose
  connections, bridge overcurrent protection
  devices and recent repair attempts.

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Electrical Equipment

• C. Evaluating equipment and applinces as
  accidental fire causes.
• 1. Light bulbs can cause ignition of combustible
  materials, however this DOES NOT occur as often
  as some investigators believe.
• 2. Temperatures generated by light bulbs depend
  on their
• a. Size (wattage)
• b. Shape (design), and
• c. Position (angle of installation)

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Electrical Equipment

• 3. Light bulbs in contact with thin combustibles
  often produce only localized scorching.
• 4. Indicators of light bulbs as a fire cause
• a. Heavy staining of bulb fragments
• b. Combustible ash may be stuck to the bulb or
  bulb fragments.
• c. A short circuit may develop near the bulb or
  socket.
• d. the point of origin may be very near

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Electrical Equipment

• e. Usually long periods of time with no occupants
  in the area of origin
• f. Laboratories may be able to determine if the
  bulb was on at the time of the fire by
  examining the filament remains

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Electrical Equipment

• 5. Lighting fixtures may cause fires in nearby
  combustible building components (joists, studs,
  insulation, etc) if improperly installed.
• a. Fire may be slow starting and be
  characteristic of low temperature ignition
  (pyrolysis).
• b. The point or area of origin may be found near
  the fixture due to very deep charring.

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Electrical Equipment

• 6. Fluorescent fixtures may malfunction or the
  ballast transformer may break down.
• a. Ballasts may contain tar like filler
  materials which will melt and run at higher
  temperatures.
• b. Improperly operating ballast transformers may
  develop extreme temperatures and self-ignite or
  ignite other nearby combustibles.
• 8 single-pin slim-line fixtures are somewhat
  famous for starting fires and/or causing problems

85
Electrical Equipment

• 7. Small electrical appliances are required to
  have thermal controls, thermostats, and/or
  overload protective devices.
• a. Controls are usually constructed of bimetalic
  strips.
• b. Control points may be pitted or fused together
  thus allowing overheating.
• c. Control points which are closed during the
  fire are usually clean and unstained.

86
Electrical Equipment

• 8. Electric motors as heat sources
• a. Bronze bearings usually do not seize-up,
  freeze, or lock, from external fire damage and
  heat, but this may indicate an internal heat
  source due to electrical overload or friction.
• b. Motor overload fuses should be examined.
• c. Contact points should be examined for fusing
  or pitting.

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Electrical Equipment

• d. Damage to the inside surface of drive belts,
  at their points of contact with pulleys, may
  indicate friction heat build-up.
• e. The clear, varnished appearance of electrical
  motor insulation, is usually burned away ONLY
  when a motor burns out from internal heat.
  External fire heat usually DOES NOT destroy motor
  wiring insulation.

88
Electrical Equipment

• f. Motors which retain high temperatures after
  other metal objects in the same area have cooled
  down, may indicate internal heating. Consider
  the metal mass of each object.

89
Electrical Equipment

• 9. Electric blankets, heating pads, and water bed
  heaters may generate heat sufficient to start a
  fire.
• a. Frequently due to an owners misuse by not
  following the manufacturers recommendations
• b. Check thermostat controls
• c. Often difficult to distinguish from fires
  caused by a cigarette in or on the mattress

90
Electrical Equipment

• 10. Televisions, radios, stereos, and home
  entertainment centers may generate enough heat to
  ignite themselves or nearby combustible
  materials.
• a. Adequate ventilation is an absolute necessity
  to allow proper operation without overheating.
• b. Dust build-up inside the set may produce
  arcing and ignite internal plastic components.
• c. Many T.V. sets operate with elevated voltages
  (up to 32,000 volts) in some areas within the set.

91
Electrical Equipment

• d. Many units fail due to their power switch
  being of a light duty design and/or possibly
  remaining in an instant on position, thereby
  allowing the set to be partially energized at all
  times generating heat.
• e. Plastic cabinets may melt, run, and burn,
  producing floor charring similar to furniture
  fires and/or liquid accelerant fires.

92
Electrical Equipment

• 11. Static electricity may cause fires.
• a. Occurs when objects of different potentials
  (or charges) contact one another.
• b. Usually occurs more during cold, dry weather.
• c. Accidental fires may occur especially in areas
  where flammable vapors/gases are present.
• d. Ground wires, straps, or clamps, may indicate
  static hazard areas.

93
Electrical Equipment

• D. Questions to be answered in any fire suspected
  to have been caused from electrical sources
• 1. Was the electricity on before the fire?
• 2. Was the electricity on at the time of the
  fire?
• 3. Did the local utility company respond to the
  fire?
• 4. Have there been any recent problems of an
  electrical nature in the building?
• 5. Have there been any blackouts or brownnouts?

94
Electrical Equipment

• 6. Have the fuses been blowing?
• 7. Have the circuit breakers been tripping?
• 8. Has the local utility company been called, or
  have servicemen been seen on the premises in
  recent days?
• 9. Do the lights seem to dim, or do they get dim
  at peak hours of electrical usage?
• 10. Do the lights flicker or dim when appliances
  are turned on?
• 11. Do appliances start or operate slowly?

95
Electrical Equipment

• 12. Does the television picture shrink or fade
  when appliances are turned on?
• 13. If there have been any electrical problems,
  what, if anything, has been done to alleviate
  them?
• 14. Has the handyman or janitor been working on
  the electrical system?
• 15. Has the owner or manager been working on the
  electrical system?
• 16. Has any other authorized or un- authorized
  person been working on the electrical system?

96
Electrical Equipment

• 17. Has an electrical contractor been working on
  the electrical system - if so, who?
• 18. Why was the electrical contractor called?
• 19. Was he called to alleviate a problem, for an
  addition, remodeling or for new work?
• 20. Is the contractor licensed?
• 21. Is there a permit for the job - if so, where
  is it?
• 22. Has the job been completed.

97
IX. Handling, storage and hazards of compressed
and liquefied gases

• A. Definition of gas The physical state of a
  substance which has no shape or volume of its
  own, but will take on the shape and occupy the
  entire volume of whatever container it occupies.
• B. Chemical classification of gases The
  chemical properties of a gas are of primary fire
  protection concern because they can react with
  other materials that can produce hazardous

98
Compressed and Liquefied Gases

• 1. Flammable gases
• a. Any gas that will burn in normal
  concentrations of air
• b. Will burn in air the same as a flammable
  liquid vapor
• c. Most flammable gases are shipped in their
  liquid state

99
Compressed and Liquefied Gases

• 2. Nonflammable gases
• a. Any gas that WILL NOT burn in any
  concentration of air or oxygen
• b. Some will support combustion (ie. oxygen) but
  others will suppress combustion (ie. carbon
  dioxide)

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Compressed and Liquefied Gases

• (1) Those supporting combustion are known as
  oxidizers and usually contain more oxygen than
  normally present in air.
• (2) Those NOT supporting combustion are known as
  inert gases (ie. nitrogen, helium, argon)

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Compressed and Liquefied Gases

• C. Physical classifications of gases
• 1. Compressed gas A gas that remains in its
  gaseous state under pressure
• 2. Liquefied gas A gas that, at normal
  temperatures inside its container, exists as
  partly liquid and partly gaseous
• 3. Cryogenic gas A liquified gas that exists in
  its container at below normal temperature, but
  slightly above its boiling point
• a. Cryogenic gases cannot be contained for an
  indefinite period of time

102
Compressed and Liquefied Gases

• b. Heat enters the container, increasing the
  temperature of the confined liquid, resulting in
  a vaporization of the contents
• c. Resulting pressure will exceed any feasible
  container strength

103
Compressed and Liquefied Gases

• D. Usage classifications of gases
• 1. Fuel gases Butane, propane, natural gas,
  manufactured gases (from coal, coke, or other
  flammable materials)
• 2. Industrial gases Entire range of gases used
  in any industrial process
• 3. Medical gases Oxygen, nitrous oxide,
  cyclopropane

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Compressed and Liquefied Gases

• E. Storage and transportation of gases Gases
  are stored, handled and transported basicly in
  three (3) types of closed, pressurized,
  containers ie. cylinders, tanks and pipelines.
  Each type requires careful design, fabrication
  and maintenance.

105
Compressed and Liquefied Gases

• 1. Cylinders (NFPA Handbook, 17th Edition)
• a. Fabricated in accordance with the United
  States Department of Transportation (DOT) or the
  Canadian Transportation Commission (CTC)
  regulations
• b. Generally limited to a maximum water capacity
  of 1,000 pounds or about 120 gallons of water
• c. Designed for a maximum service pressure

106
Compressed and Liquefied Gases

• d. Designed to contain a specific gas or group of
  gases
• e. Require specific safety devices
• f. Other specifications cover metal
  composition and physical testing, wall thickness,
  joining methods, nature of openings in the
  container, heat treatments, proof testing, and
  marking.

107
Compressed and Liquefied Gases

• 2. Tanks (NFPA Handbook, 17th Edition)
• a. Usually fabricated in accordance with
  standards published by either the American
  Society of Mechanical Engineers (ASME) or the
  American Petroleum Institute (API).
• b. ASME tanks are covered by their Boiler and
  Pressure Vessel Code and are usually smaller
  tanks under moderate pressure.

108
Compressed and Liquefied Gases

• c. API tanks are covered by their tank
  fabrication standards and are usually very large
  tanks under low pressure.
• d. Cylinders or tanks that are part of
  transportation units such as cargo vehicles or
  railcars, are subject to additional regulations
  of the DOT or CTC, generally reflecting the fact
  that the containers are on wheels.

109
Compressed and Liquefied Gases

• e. Cylinders or tanks containing liquefied
  petroleum gas (LPG), compressed natural gas
  (CNG), or liquefied natural gas (LNG), are
  regulated in Texas by safety rules of the LPG
  Division of the Texas Railroad Commission.

110
Compressed and Liquefied Gases

• 3. Pipelines (NFPA Handbook, 17th Edition)
• a. Natural gas, LP Gas, anhydrous ammonia,
  oxygen, hydrogen, and other gases used in large
  volumes, are often transported by pipeline.
• b. Most pipelines transporting or distributing
  flammable gases have been regulated since 1968 by
  the DOT Office of Pipeline Safety, and are
  covered by federal regulations.

111
Compressed and Liquefied Gases

• c. DOT regulations cover such items as pipe
  materials, design for pressure and other
  stresses, piping components including valves,
  joining methods, installation of meters, service
  regulators and service lines, testing
  requirements, and other items.

112
Compressed and Liquefied Gases

• F. Safety Considerations
• 1. Contained compressed gas hazards and
  safeguards
• a. Compressed gas (solely in a gaseous state)
  simply expands when heated and generally follows
  basic gas behavior laws, generating more pressure
  in the container.

113
Compressed and Liquefied Gases

• b. Additional pressure generally is relieved by
  an overpressure relief device.
• (1) Spring-loaded valve
• (2) Bursting disk
• (3) Fusible plug
• c. Flammable gases should not be stored with
  nonflammable gases, but should be separated by at
  least 20 feet.

114
Compressed and Liquefied Gases

• 2. Contained liquefied gas hazards and safeguards
• a. Liquefied gases, including cryogenic gases,
  exhibit more complicated behaviors because the
  net end result of heating is the combination of
  three effects
• (1) The gas phase is subject to the same effects
  as a compressed gas

115
Compressed and Liquefied Gases

• (2) The liquid attempts to expand, compressing
  the vapor, and
• (3) The vapor pressure of the liquid increases as
  the temperature of the liquid increases.
• b. The relieving capacity of pressure relief
  devices is based upon the discharge of gas, not
  liquid.

116
Compressed and Liquefied Gases

• 3. A BLEVE (Boiling Liquid Expanding Vapor
  Explosion) is a pressure-release explosion.
• a. Results FROM container failure
• b. Even though an overpressure relief device
  functions properly as designed, BLEVEs may still
  occur because of the circumstances present at the
  time.

117
Compressed and Liquefied Gases

• G. Ignition sources and conditions conducive to
  ignition
• 1. The major and most dangerous source of
  ignition is exposure of pressure containers to
  external heat sources, such as flame impingement,
  resulting in a BLEVE.
• 2. Other sources of ignition stem from escaping
  gases traveling to an open flame or spark, and
  igniting.

118
Compressed and Liquefied Gases

• H. Gas fires and explosions
• 1. Gas fires
• a. Destruction of fuel lines during a fire may
  increase the burn rate and the resulting charring
  may appear unnatural.
• b. The point of origin may be located in the area
  of a gas appliance, which would require
  confirmation that the appliance malfunctioned.

119
Compressed and Liquefied Gases

• 2. Gas explosions
• a. The type of structural damage may indicate the
  type of explosive fuel (gas) involved.
• (1) Natural gas and manufactured gas are
  lighter than air and will rise to upper levels of
  a structure, usually resulting in damage being
  centered in the upper levels of the area involved.

120
Compressed and Liquefied Gases

• (2) LP Gases, such as butane and propane are
  heavier than air and generally settle to lower
  levels of a structure resulting in more damage to
  the lower levels of the area involved.
• (3) All flammable liquid vapors are heavier
  than air and will normally settle to the lower
  levels of a structure, usually producing more
  damage centered at the lower levels of the area
  involved.

121
Compressed and Liquefied Gases

• 3. Explosions may occur during attempted suicides
• a. Many people wrongly believe natural gas and
  LPG to be poisonous, and may attempt to use gas
  fueled cooking equipment to commit suicide.
• b. Check for extinguished pilot lights and
  controls set on HIGH.

122
X. Combustible Dusts

• A. Most finely divided combustible materials are
  capable of igniting and burning or exploding.
• 1. Agricultural products, ie. wood, starch,
  sugar, corn
• 2. Carbonaceous dusts, ie. coal, charcoal, coke,
  soot
• 3. Chemical dusts, ie. sulphur, lactose, ascorbic
  acid, lead stearate, methyl celulose
• 4. Metal dusts, ie. aluminum, bronze, iron,
  magnesium, zinc

123
Combustible Dusts

• B. Deposits of combustible dust on beams,
  machinery, and other surfaces, are subject to
  flash fires.
• C. When combustible dust particles are suspended
  in air and ignited, they may explode.

124
Combustible Dusts

• D. The chance of a dust cloud igniting is
  governed by
• 1. The size of its particles
• 2. The dust concentration
• 3. Impurities present
• 4. Oxygen concentration
• 5. Strength of the source of ignition

125
Combustible Dusts

• E. Dust explosions generally occur as a series
• 1. Small cloud explodes, creating more dust
• 2. Larger cloud ignites and explodes, etc.
• F. The hazard of any given dust is relative to
  its ease of ignition and the severity of the
  ensuing explosion.
• G. The small the dust particle, the easier it
  ignites

126
Combustible Dusts

• H. Dust clouds have been ignited by open flames,
  lights, smoking materials, electric arcs, hot
  filaments of broken light bulbs, static sparks,
  welding and cutting torches, and other common
  heat sources

127
Combustible Dusts

• I. Destructiveness of a dust explosion depends
  primarily on the
• 1. Rate of pressure rise
• 2. Maximum pressure developed
• 3. Duration of the excess pressure
• 4. Degree of confinement
• 5. Oxygen concentration

128
Combustible Dusts

• J. It is the total duration of excess pressure,
  rather than the force exerted at any one moment,
  that will determine the amount of destruction
• K. The involved area may appear to have suffered
  a flash fire with NO SINGLE POINT OF ORIGIN.

129
XI. Flammable and Combustible Liquids

• A. Definitions
• 1. Flammable liquids Liquids having a flash
  point BELOW 100 degrees F.
• 2. Combustible liquids Liquids having a flash
  point AT or ABOVE 100 degrees F.

130
Flammable and Combustible Liquids

• B. Misuse of flammable/combustible liquids may
  cause accidental fires
• 1. Improper storage
• a. Can occur in almost any storage area
• (1) Residential occupancies
• (a) Utility rooms
• (b) Kitchen cabinets
• (c) Bathrooms
• (d) Garages/carports

131
Flammable and Combustible Liquids

• (2) Commercial/industrial occupancies
• (a) Offices
• (b) Plant or work areas
• (c) Storage closets
• (d) Warehouse area