Welcome and Thank You Tonight I will be giving you information that is covered in 24 class hours in about 20 minutes to help you understand what the firefighters are looking at and to help you understand how a wildfire will impact your home. I will be going fast so tighten you seat belts and jot any questions down for the end. First a quick video of some Denver firefighters at the Black Forest Fire to give you some feel of being in a wildfire.
Genesee Fire Rescue, Genesee community and State and Federal athorities are all linked together in an effort make the potential fire event safer.
Following is a slide and video presentation designed to help you understand what fire can do and how to prepare your home.
Any slide that says “click image to play video” will take you to a YouTube video we have prepared for you.
It takes 3 components to have fire: Oxygen – Heat – Fuel. Remove any one of these and no more fire. Water removes Heat / foam and dirt remove Oxygen / fire line and mitigation removes Fuel.
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Convection
Radiation
Conduction
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Oxygen and Fuel are everywhere – so how does the Heat spread? Convection – heat rises Conduction – heat transfers directly from one fuel source go another by direct contact Radiation – this is the heat you feel when you stand in front of your fireplace
Temperature Wind
Increases supply of oxygen. Drives convective heat into adjacent fuels. Influences direction of spread and spotting. Carries away moist air replacing it with drier air. Dries fuels. Raises fuel moisture if the air contains moisture.
Relative Humidity As RH increases, fuel moisture increases.
Precipitation Increases fuel moisture
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There are 4 parts of weather that impact fire behavior: Temperature – preheats fuels in direct sunlight and lowers RH Wind – RH Relative Humidity – impacts fuel moisture Precipitation -
Strong Wind. Sudden changes in wind direction and velocity due to
weather fronts. High, fast-moving clouds may indicate unusual surface
winds. Unexpected calm may indicate wind shift. Thunderstorms above or close to the fire. Unusually high temperatures and low relative humidity. Dust devils and whirlwinds developing. Bent smoke column.
Weather Indicators
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Not much we can do with the weather other than watch for warning signs and try to predict weather that may cause problem fire behavior
SOUTH
NORTH
Heavy fuels Shade Moist
Light fuels Sunny Dry
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Example: Driving down I-70 towards Denver
Flame is closer to
and preheating
fuel
Convection and Radiant Heat
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Fire moves approximately 17 times faster than on level ground
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Like a chimney, the canyon will draw the air up it and in doing so will increase the wind speed and the rate of spread and intensity of the fire. Air want equilibrium. As the Hot air rises and creates void so that surrounding air will rush in achieve equilibrium – sort of like a mini low pressure system. GENESEE
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You get the effects of a chimney and embers have a shorter distance to travel and start spot fires.
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Water flowing in a stream
Steep slopes. Chutes, saddles, and box canyons which
provide conditions for “chimney effect.” Narrow canyons may increase fire spread
These are the 5 characteristics we look at regarding fuels
The amount of water in a fuel expressed as a percentage of the
oven-dry weight of that fuel.
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Determines how well a fuel will ignite and burn. Dry fuels will ignite and burn much more easily than the same fuels when they are wet. Before a wet fuel can burn, the moisture it contains must evaporate. 1-hour0.0 to 0.25 inch diameterGrass, pine needles, etc. 10–hour0.25 to 1 inch diameterComputed from observation time temperature, humidity, and cloudiness. 100–hour1 to 3 inches diameterComputed from 24–hour average conditions composed of day length, hours of rain, and daily temperature/humidity ranges. 1000–hour3 to 8 inches diameterComputed from a 7–day average conditions composed of day length, hours of rain, and daily temperature/humidity ranges.
Light Fuels: Leaves Grass Shrubs
Heavy Fuels: Limbs Logs Stumps
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The higher the ratio of Surface Area to Volume of a fuel, the easier to ignite. Takes more BTUs to ignite larger fuels with lower Surface to Volume ratios
The quantity of fuels in an area
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Simply put it is the amount of fuel in an area. grass, brush, trees, structures Usually expressed in Tons Per Acre
Horizontal Continuity: Uniform Patchy
Vertical Arrangement: Ground Surface Aerial
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Uniform: fuels distributed continuously over the area Patchy: fuels distributed unevenly over the area, or areas of fuel with definite breaks or barriers present.
Vertical Arrangement of Fuels
Aerial Fuels
Ladder Fuels
Surface Fuels
Ground Fuels
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GROUND FUELS: All combustible materials lying beneath the surface including: deep duff, roots, rotten buried logs, peat, other organic material SURFACE FUESL: All materials lying on or immediately above the ground including: needles, leaves, grass, downed logs, stumps, large limbs, low shrubs LADDER FUELS; Any fuels that provide a connection between the surface and upper canopy. AERIAL FUELS: All green and dead materials located in the upper forest canopy including: tree branches, crowns, snags, moss, high shrubs
Unusually dry fuels. Large amount of light fuel (shrubs, grass,
needles). Fuels exposed to direct sunlight. Fuels dried by prolonged drought. Ladder fuels that allow a surface fire to move
into the crowns of shrubs or trees. Crown foliage dried by surface fire. Concentration of snags.
Fuel Indicators
Fire Behavior Terms
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Fire burning with a low flame and spreading slowly.
Fire producing sparks or embers that are carried by the wind or convection that start new fires
*Click on image to play video
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Spotting occurs when small burning embers land outside the fire perimeter and start small fires.
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torching is characterized when trees occasionally burn from bottom to top. Torching can happen with individuals trees or small clusters of trees. Torching is frequently isolated and intermittent. This may be an indicator that fire behavior is increasing
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Fire advances from top-to-top of trees or shrubs more or less independently of the surface fire.
*Click on image to play video
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Crowning occurs when a surface fire moves into and burns in the canopy of trees, independent from the surface. This is a very hazardous situation and tactics usually will involve air support and indirect attack
A spinning, moving column of ascending air rising within a vortex and carrying aloft smoke, debris, and flames.
*Click on image to play video
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Spot fires Falling of snags and shallow rooted trees
Keep an eye on the smoke column. Indicates direction of fire spread, location of spot fires, and changes in fire intensity.
Many simultaneous fires starting or smoldering fires beginning to pick up in intensity.
Fire begins to torch small groups of trees or shrubs. Frequent spot fires occurring. Fire-whirls beginning to develop inside the main fire. Crown fires.
Fire Behavior Indicators
Offensive
Defensive
Combination
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The Basic Tactics we use
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Attack and contain the fire
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Engine and crew DIRECTLY ATTACK the fire With hand tools where flame lengths are no higher than 4 feet Engine attack hose line where flame lengths are up to 8-10 feet and you have sufficient water
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Set up at the house Clear flammable material Protect house from flame and sparks
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Note the engine is set up so it is protected from the radiant heat by the structure The crew will prep the house if time permits and would pull hose lines so that they can reach around the house with water And direct the fire around it. This is dependant upon fuels around the structure and escape routes.
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If too much fire or no defensible space, LEAVE! Return after fire front passes
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If time permits, the crew will prep the structure (in this picture they applied foam) and then retreat to a safety zone and wait. This tactic is most successful where homes have been mitigated and one I have used very successfully several time. It is also safer for the firefighters
Structure engines at home for protection
Attack fire and and drive flames away from house
# 1
# 2 # 3
# 4
Structure Triage “Size-Up”
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One engine with 500 gallons of water and a crew of 4. What actions are you going to take? You know another engine is 5 minutes behind you – now what do you do?
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1. Well-irrigated area encircling structure for at least 30 feet on all sides. Plantings limited to carefully spaced low flammability species.
2. Provide added protection with “Fuel Breaks” like driveways, gravel walkways and lawns.
Case Study of Witch and Guejito Fires
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NIST – National Institute of Standards and Technology These are the first case study evaluating fire mitigation and at the same time factoring in ember exposure and defensive actions. As we go through these you will notice how what we talked about earlier applies. As we do not have manicured, irrigated lawns in Genesee, the takeaway here is to use low flammability species for your landscaping. Not ground cover juniper. Trim the grass to the dirt near any wood siding and decks. There are a few homes in the area where they have created areas of river rock around their house
3. Keep vegetation pruned and limb trees 6–10 feet from ground. Remove leaf /needle clutter and dead and overhanging branches.
4. Periodically inspect your property, clearing
dead wood and dense vegetation at a distance of at least 30 feet from your house.
5. Is the structure free of an attached wood fence?
Footnote: Of the 241 homes impacted, 13 had wood shake roofs and all 13
were destroyed. A total of 89 were destroyed or damaged.
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3. How many times have your heard this one? The two takeaways we saw first hand at the Black Forest Fire were “keep your gutters clean” and “don’t use landscaping timbers in retaining walls” 4. Just because you did major mitigation work last year does not mean it does not need to be maintained 5. Continuity of fuels - Footnote: Of the 241 homes impacted, 13 had wood shake roofs and all 13 were destroyed. A total of 89 were destroyed or damaged.
*Click on image to play video
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This video is a couple of minutes and I would like you to Note the embers falling and blowing across the pavement as you watch.