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Developed by Dave Dodson, Battalion Chief (ret.), Colorado

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1 Developed by Dave Dodson, Battalion Chief (ret.), Colorado
Reading Smoke “Reading Smoke” Developed for the Everyone Goes Home Resource Kit by Dave Dodson, Battalion Chief (ret.) Opening Photo from South Metro Fire Rescue Authority, CO. “Reading Smoke” is a skill, used by first-due decision-makers, to help make judgments about anticipated fire behavior in structures. Developed by Dave Dodson, Battalion Chief (ret.), Colorado

2 Preparing to use this program:
View the “Reading Smoke” video on DVD #1 prior to delivering this program Review Reading Smoke Lesson Plan Prepare by finding raw fireground footage to use in order to practice “Reading Smoke” (See slide “Practice Examples” for usable websites)

3 The Reading Smoke Process
Reading Smoke can help you answer 3 questions: Where, specifically, is the fire? How big or intense is the fire? How fast is the event changing? (rate and severity of fire spread) Smoke actually paints a better picture of fire potential than flames. Retired LA City Battalion Chief John Mittendorf once said: “Read the smoke, it’s the fire talking to you!” IF you can answer the three questions, you’ll make better decisions regarding tactics (i.e.: ventilation priorities, line size, attack location, rescue profile, etc.).

4 Basic Process – the Science
3 concepts: Smoke is FUEL The fuels have changed – more continuity and explosiveness than previously taught The smoke has trigger points: right temperature and right mixture The ability to reading smoke is actually founded in the understanding of fire science. Smoke is Fuel: Smoke is defined as the product of incomplete combustion or pyrolitic decomposition that includes particulates (solids), aerosols (liquids), and gases. In other words – smoke is the fire load of a building in a moving form! The fuels have changed: Low-mass or high-surface-to-mass plastics are to blame. The changes really took hold in the late 1990s. Now, fire behavior in a typical suburban residential fire is so dramatic and severe that the fire science community is re-writing text books! The smoke (fuel) has trigger points that will cause it to ignite or explode. For smoke to self-ignite, it must be in the right mix with air (flammable range) and gases within the smoke must be above their auto-ignition temperatures. In rare cases, smoke can ignite below its auto-ignition temperature provided the gases are above their flash-/fire-point, have a supply of air, and become exposed to a spark or flame. Photo by Keith Muratori

5 Consider this… The following gases create “ladder fuels” within smoke (remember, there are particulates and aerosols also). Gas Self-Ignition Temperature Flammable Range Acrolein 450°F 3-31% Benzene 928°F 1-8% Hydrogen Cyanide 1000°F 5-40% Carbon Monoxide 1123°F 12-74% These prevalent gases give smoke aggregate fire properties: The smoke can ignite as low as 450 degrees F in mixtures as wide as 1%-74% in air. That makes smoke an amazingly contiguous fuel. “Ladder Fuels” refer to the simple concept that the Acrolein will ignite first (lowest ignition temp.) which will in turn burn and heat the benzene to its ignition temperature, which triggers the ignition of HCN and CO. This can happen in just a few seconds.

6 The Basic Process (cont.)
Process Rules: Nothing is absolute Compare ventilation openings (restricted or unrestricted, smoke or no smoke) Start measuring rate of change (seconds or minutes) Just like any procedure or process, some application guidelines or rules must be understood. Fires are far from absolute due to the many factors that impact fire growth and the dynamic rate of change that can take place – it is for this reason the art of “Reading Smoke” is just as dynamic. The size of an opening or the resistance of a crack will ultimately impact the speed that smoke can leave the building. Compartmentalized fires are always in a state of change. Firefighters must judge whether smoke conditions are getting better or worse – in seconds or in minutes. Photo courtesy: Rosemount Fire Department

7 The 3 Steps for “Reading Smoke”
Inventory & compare smoke attributes: volume, velocity, density, and color Factor in influences that change the meaning of VVDC Answer the questions Reading Smoke includes three steps. The hardest part is step 1 – firefighters must break their natural habit of categorizing smoke as merely “light” or “heavy.” Smoke has four attributes or characteristics: volume, velocity, density, and color. We will explain these attributes in the next few slides. Step 2 takes into consideration influences such as weather and compartment size which can alter the meaning of volume, velocity, density, and color. The questions refer to the 3 we mentioned before: where’s the fire, how big or intense is the fire, and what is the fire going to do next? Photo by Steve Redick

8 STEP 1: Inventory and compare the key attributes
Volume Velocity (Pressure) Density Color Each are explained in the next four slides.

9 VOLUME Gives an impression Establishes relativity to the “box”
Remember: a small volume of smoke from a very large box is significant Volume is a source of pressure (velocity) Volume of smoke is relative to the size of compartment the smoke is leaving. By itself, smoke volume can only give you an impression about the fire. Photo by Steve Redick

10 VELOCITY (Pressure) How fast is the smoke leaving?
Turbulent or Laminar? Is laminar heat or volume pushed? Compare velocity from like-sized openings to find fire location Smoke Velocity refers to the speed and flow characteristic. Flow characteristic can be classified as “turbulent” (severely agitated smoke) or “laminar” (smooth, cooling smoke). If smoke is turbulent, flashover is imminent. Laminar smoke means that the smoke has traveled some distance and has lost heat. All things being equal, the fastest, most excited smoke will be closer to the fire. EMPHASIZE: Turbulent smoke means FLASHOVER is ready! Photo: Summerville Fire Department

11 Density Most Important Factor Tells you the future Continuity of Fuel
Likelihood of an Event “Degree” of the Event Smoke density is the most important factor in that it helps you predict fire growth. The thicker smoke is – the more fuel continuity exists within the building. Obviously, if fuel continuity is high, the more explosive (rapid) and wide-spread fire behavior will become. Photo by Dave Dodson

12 Color Tells Stage of Heating
Should compliment velocity to find location of fire “Brown” Smoke is usually unfinished wood being heated Remember, smoke color can be filtered over distance or through resistance Smoke color is more indicative of heat than type of material burning. White smoke usually means early-stage heating of fuels whereas black smoke is late-stage heating. Carbon and Hydrocarbons (aerosol oil droplets) make smoke black – and both of these are sticky. So, as smoke travels through a building, the black color may be lost even if the smoke is still hot. This will appear as whiter smoke also. To tell the difference between cool white and hot white – look at the velocity of the smoke. Cool should be slow – hot white will have speed. Brown smoke means that unfinished wood is being heated and is ready to ignite. Typically, the only unfinished wood in a building is the structural components. Brown smoke coming from structural areas of newer, lightweight engineered wood buildings is a warning sign of collapse! Photo by Steve Redick

13 STEP 2: Factor in Influences
Container (defines the significance of VVDC) Weather The size of compartment that smoke is leaving helps the fire officer understand the significance of VVDC. For example: low volume, slow velocity, thin, and white smoke should indicate a small fire – that is true if the compartment is small. The same characteristics showing from a big-box store like Home Depot would be alarming – expect a big fire. Weather also changes smoke VVDC. Wind should be obvious. Hot/dry weather allows smoke to rise or disperse. Hot/humid air will allow smoke to rise but stay together. Cold air can cause smoke to cool and fall very quickly. Photos collected by Mike Scott.

14 STEP 3: Answer the Questions
Where’s the fire? How big or intense is the fire? How fast is it changing? (rate and severity) If these questions can be answered, the first-due decision-maker will design better tactical solutions. Photo from Friday Harbor Fire Department

15 Always Remember: Velocity trumps color
ANY thick, fast moving smoke is ignitable Zero visibility makes you a slave to your environment Review key points above Photo by Bill Craddock

16 Single Most Important Point:
Turbulent smoke is ready to flash – and indicates that floor temperatures are past human life thresholds (zero rescue profile!) Manage it – but reduce your risk-taking! This point can’t be over-emphasized: Turbulent means FLASHOVER! Photo from

17 Use raw fireground footage from your department, or from the internet:
Practice Examples Use raw fireground footage from your department, or from the internet: (search on house fires or flashover) There are many sources to use. A good place to start is or

18 Be Safe – Make it Safe ! For more information on Reading Smoke
contact Dave Dodson at Questions and comments can be forwarded to the author: Dave Dodson. His is

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