Module A Fire Behavior Battery C36 FF3 Mod A

This law gives the relationship between volume and temperature if pressure and amount are held constant. If the volume of a container is increased, the temperature increases. If the volume of a container is decreases, the temperature decreases. Suppose the temperature is increased. This means gas molecules will move faster and they will impact the container walls more often. This means the gas pressure inside the container will increase (but only for an instant.) Think of a short span of time. The greater pressure on the inside of the container walls will push them outward, thus increasing the volume. When this happens, the gas molecules will now have farther to go, thereby lowering the number of impacts and dropping the pressure back to its constant value.  Charles’ Law: This law gives the relationship between volume and temperature if pressure and amount are held constant. If the volume of a container is increased, the temperature increases. If the volume of a container is decreases, the temperature decreases. Suppose the temperature is increased. This means gas molecules will move faster and they will impact the container walls more often. This means the gas pressure inside the container will increase (but only for an instant.) Think of a short span of time. The greater pressure on the inside of the container walls will push them outward, thus increasing the volume. When this happens, the gas molecules will now have farther to go, thereby lowering the number of impacts and dropping the pressure back to its constant value.

An example of Charles's Law would be what happens when a hot air balloon has air heated. The air expands and fills the balloon. Of course, other physical principles cause the balloon to rise against the gravitational force. As the air inside the balloon expands the balloon gets bigger and displaces more air. The displaced air produces a buoyant force that counters the gravitational force and causes the balloon to rise.

 Boyles Law- His law gives the relationship between pressure and volume if temperature and amount are held constant. If the volume of a container is increased, the pressure decreases. If the volume of a container decreases, the pressure increases. Suppose the volume is increased. This means gas molecules have farther to go and they will impact the container walls less often per unit time. This means the gas pressure will be less because there are less molecule impacts per unit time.  If the volume is decreased, the gas molecules have a shorter distance to go, thus striking the walls more often per unit time. This results in pressure being increased because there are more molecule impacts per unit time.  The mathematical form of Boyle’s Law is: PV=k.  This means that the pressure-volume product will always be the same value if the temperature and amount remain constant.

 A practical application illustrating Boyles Law would be the action of a syringe. When we draw fluids into a syringe, we increase the volume inside the syringe, this correspondingly decreases the pressure on the inside where the pressure on the outside of the syringe is greater and forces fluid into the syringe. If we reverse the action and push the plunger in on the syringe we are decreasing the volume on the inside which will increase the pressure inside making the pressure greater than on the outside and fluids are forced out.

 Heat of compression:  Heat of compression: Generated when a gas is compressed. Due to the fact that the property of a certain gas is directly related to its molecular structure at ambient temperature, and since molecules are constantly in motion even at times colliding into each other, when that gas is compressed the molecules that make up that gas are made to contact each other more often, the increase in friction causes the temperature of the gas to rise.  Example: diesel engine.

Types of fuel:  A. Duff:  a) Small Twigs, roots, soil (peat)  b) Leaves  c) Needles on ground  d)Very hard to extinguish, can become deeply seated fires.

 Types of fuel:  B. Surface Fuels:  a) Living vegetation  b) Examples:  i) Grass  ii) Brush  iii)Heavy limbs

 Types of fuel:  C. Crown Fuels:  a) Suspended and upright fuels  b) Separated from ground fuels to extent air can circulate freely around them increasing chance of ignition.  c) Examples:  i) Branches  ii) Moss  iii) Snags

 A. Fuels size: Smaller fuel particles (light or flash fuels) ignite easier and burn faster. Can also include field crops.  B. Compacted fuels burn slower.  C. Continuity: Fuels close together spread fire faster. Horizontally or vertically.  D. Volume: The more fuel, the greater the intensity.

 E. Wind:  a) Fans fire into greater intensity.  b) Supplies fresh air.  c) Dries damp areas.  d) Can be created by medium or large size fires as well.  F. Temperature:  a) Affects winds.  b) Related to relative humidity.  c) Has drying effect.

 G. Relative Humidity: impacts dead fuels because of moisture content.  H. Precipitation: moisture content.  I. Steepness of Slope:  a) Affects rate of fire spread.  b) Affects direction of travel  C) steeper the slope faster the spread.

 J. Slope Aspect: Southern exposures burn faster.  K. Local terrain features: Air movement.  L. Canyons: Increase wind velocity.

 British Thermal Unit (BTU): Amount of heat necessary to raise the temperature of one pound of water, one degree Fahrenheit.  Fahrenheit (  F): Temperature scale based on the freezing point (32  ) and boiling point (212  ) of water.  Daniel Gabriel Fahrenheit (b. May 24, 1686 in Gdansk,died Sept. 16, 1736, The Hague)

 Celsius (  C): Temperature of scale based on the freezing point (0  ) and boiling point (100  ) of water.  Calorie (C): Amount of heat necessary to raise the temperature of one gram of water one degree Celsius.

 A. Surface to mass ratio:  a) Ratio of surface area of the fuel to the mass of the fuel.  b) As ratio increases, fuel particles become smaller and more finely divided thus greatly increasing the chance of ignitability.  c) As surface area increases, heat transfer is easier and the material heats easier thus accelerates pyrolysis.

 B. Positioning: Vertical vs. horizontal- fuel stacked vertically increase likely hood of fire extension. This is due to super heated air rising and converting the vertically stacked material via pyrolysis into fuel much quicker.

IDENTIFY THE HAZARD OF FINELY DIVIDED FUELS AS THEY RELATE TO THE COMBUSTION PROCESS (4-5.1):  C. Moisture content: Dry vs. moist materials. Obviously drier materials are more likely to burn quicker.  D. Arrangement (air): material packed tightly v. material that is loosely packed.

 Flash point: Minimum temperature at which a liquid gives off sufficient vapors to ignite momentarily near the surface of a liquid. Vapors will flash but will not burn.  Fire point: Temperature at which liquid gives off sufficient vapor to support combustion once ignited.  Ignition temperature: Minimum temperature to which a fuel, in air, must be heated to start self- sustained combustion without outside ignition source.

 Law of Specific Heat: The measure of the heat absorbing capacity of a substance. Amount of heat transferred is measure in BTU’s. Specific heat represents the amount of heat necessary to raise the temperature of a specified quantity of a material and an equal amount of water.

 Latent heat of vaporization: Quantity of heat absorbed by a substance when it changes from liquid to a vapor. Raising temperature of one pound of water from 60  to 212  F requires 152 BTU’s. To change water at 212  F to steam vapor of the same temperature, requires an additional 970 BTU’s of heat energy (latent heat). Latent heat explains potential extinguishing capacity of water.

 Chemical:  A. Heat of combustion: oxidation reaction, varies depending upon material type, why some materials burn hotter.  B. Spontaneous heating: organic substance, occurs where sufficient air not present and insulation prevents heat dissipation.  C. Heat of decomposition: release of heat from decomposing materials usually bacterial, ex: compost piles.  D. Heat of solution: heat released by the solution of matter in liquid, some acids.

 Mechanical:  A. Friction: created by the movement of 2 surfaces against each other.  B. Compression: generated when a gas is compressed, diesel engine, SCBA bottle filling.

 Electrical energy:  A. Resistance heating: generated by current passing through conductor, increased if wire is not large enough, too much pull on system.  B. Dielectric heating: result of pulsating AC or DC at high frequency on non- conductive materials, substance heated by being in constant contact with electricity.  C. Leakage current heating: occurs when wiring is not insulated well enough to contain all the current, current leaks out of wires and heats surrounding materials, outlet in wall mounted to a wall stud.

 Electrical energy: (cont.)  D. Heat from arcing: occurs when current flow is interrupted, may be from a switch or loose connection.  E. Static electricity: buildup of positive charged on one surface and a negative charge on another surface.

 Type 1 construction:  1. Designed to compartmentalize fire spread.  2. Building itself is made of fire noncombustible or limited combustible materials.  3. Provides structural integrity during a fire.  4. Primary hazards is building contents  5. Protection may be compromised:  a) Opening in partitions.  b) Improperly designed HVAC system (dampers)  6. Interior attack can be done with a greater deal of confidence.

 Type 2 construction:  a) Primary concern is contents of building.  b) Heat build up can cause structural collapse. Steel trusses will absorb heat and can fail very quickly (5-15 minutes).  c) Materials with no fire resistance ratings may be used (ex: untreated wood)  d) Usual have flat, built-up roofs. These roofs can contain felt, insulation, and roofing tar.  e) Fire extension can easily spread to roof and cause roof collapse.

 Type 3 construction (ordinary):  a) Exterior walls and structural members are noncombustible or limited combustible materials.  b) Interior structural members (walls, columns, beams, floors, and roof are completely or partially constructed of wood, which the wood is of a diameter much smaller than heavy timber construction.)  c) Fire and smoke spread through concealed spaces.  d) Heat may be conducted to concealed areas through finish materials (drywall, gypsum board or plaster).  e) Fire may burn within concealed spaces and if conditions are right (hot enough)/  f) Hazards can be reduced by placing fire stops inside concealed spaces.

 Type 4 construction (heavy timber):  a) Primary hazard is massive amount of combustible members.  b) Because of heat given off by structural members it presents serious exposure hazards.

 Type 5 construction (wood frame):  a) Almost unlimited potential for fire extension throughout structure.  b) Concern for extension to exposures.