The ART of READING SMOKE
Developed By: Dave Dodson Former Battalion Chief & Duty Safety Officer Lead Instructor – Response Solutions, LLC
The Art of Reading Smoke
Fighting fires has never been more challenging - composites, lightweight construction, engineered structures, and unusual fuels will cause hostile fires to burn hotter, faster, and less predictable.
As a Fire OFFICER – or Firefighter - you MUST be able to predict fire behavior and hostile fire events. If you don’t or can’t, firefighters will die or be critically injured. The key to predicting fire behavior is directly related to your ability to READ SMOKE as you arrive and begin firefighting operations.
This class will help you discover the ART of READING SMOKE!
Why do we “Read Smoke?
Reading smoke helps you discover the specific location and intensity of a fire, building collapse potential, and the likelihood of a hostile fire event like flashover. If you can discover these things – you can make better strategic and tactical decisions! In order to read smoke, you must have a foundation in some basics:
First, you must know the Advanced Basics:
Concept #1: “Smoke” is FUEL! Firefighters use the term “smoke” when addressing the solids, aerosols, and gases being produced by incomplete burning or heat degradation of contents (pyrolysis).
1. Smoke Solids 70% of smoke is particulate (mostly carbon) Carbon (soot) is black Ash is dirty white (trace minerals and metals that carry heat) Particulates can cause a fire in a compartment to become vent-restricted
2. Smoke Aerosols Water – clean/uniform white when visible Hydrocarbons – black droplets/mist Oil/tar droplets can have self-ignition temperatures as low as 460°F
3. Smoke Gases Thousands of gas types in smoke – most have no color Most are transient and trace Typical gases that impact fire behavior are Carbon Monoxide, Hydrogen Cyanide, Benzene, and Acrolein See chart (next page) for properties “Ladder fuels” Gases also create “continuity of fuel” throughout box
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Properties of Gases Typically Found in Smoke
Gas Flashpoint Self- Flammable Notes Ignition Range in Air Temp. Carbon See notes 1128ºF 12-74% CO is considered a gas only–and, Monoxide therefore, doesn’t have flashpoint. (CO) The flammable range of CO is 12-74 only at the ignition temperature. Hydrogen 0°F 1000°F 5-40% HCN is produced when high Cyanide temperatures break down nitrogen- (HCN) containing products. HCN is quite flammable and is considered extremely toxic. Benzene 12°F 928°F 1-8% Most plastics release benzene while (C6H6) burning or pyrolyizing. Benzene is also a common product from the burning of fuel oils.
Acrolein -15°F 450°F 3-31% Acrolein is a by-product from the (C3H4O) incomplete combustion of wood, wood products, and other cellulosic materials. Poly-plastics can also render acrolein.
Source: http://www.cdc.gov/niosh/npg/npg.html
Concept #2: The Fuels have changed: The contents and structural elements being heated or burned are of LOWER MASS than previous decades. These materials are also more synthetic than ever.
Concept #3: The Fuels have trigger points: There are “Triggers” for Hostile Fire Events: These triggers are simply “right temperature” and “right mixture.” Flash Point can trigger a smoke explosion. Fire Point triggers rapid fire spread. Ignition temperature triggers auto ignition, backdraft, and flashover.
Flash Point: The lowest temperature a fuel will off-gas an ignitable mixture that will simply flash – but not SUSTAIN, given a spark or flame.
Fire Point: The lowest temperature a fuel will off-gas an ignitable mixture that will ignite and continue to burn given a spark or flame.
Ignition Temperature: The lowest temperature a fuel will off-gas an ignitable mixture that can self-ignite.
Burnable gases must be in their right percentage with air to ignite. In hostile fires, a gas may be hot enough to self-ignite – but is too rich to burn. Firefighters’ efforts can cause this ignition.
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Second, the “new” compartment fire can transition through SIX PHASES!
Turbulent vs. Laminar Flow The MOST important smoke observation to make on arrival is the smoke-flow characteristic:
Turbulent = flashover Laminar = box is still absorbing
REMEMBER the “human life” thresholds: 195F for the airway and 300F for Skin (1 minute exposure).
SOME “OVERHEAD” RULES FOR “READING SMOKE”:
The Process:
1. Trying to answer three questions: Where (exactly) is the fire? How big or intense is the fire? What is the fire going to do? (what will it look like in 2 minutes?)
2. Focus on smoke – not flames Easy to say – hard to do Psychological attraction – “find the fire” focus Physiological attraction (pupils)
3. Where is there smoke? Where isn’t there smoke?
4. Look at windows! Windows clear = <160°F Windows wet = 160-190°F nearby Windows black-stained and heat cracked = Reduced life survivability
4 Dodson 5. Turbulent vs. Laminar is perhaps the first and most important smoke observation
6. Capturing “rate of change” is second most important concept. Remember: A fire can grow ten times its volume in a few seconds in today’s fires!
7. Hostile warning signs Flashover = Turbulent smoke, rollover Backdraft = closed box pressurized, yellowish smoke Rapid Spread = smoke speed is accelerating Smoke Explosion = trapped smoke above fire
The 3-STEP process to READING SMOKE:
STEP 1: INVENTORY the KEY ATTRIBUTES of smoke:
Volume = Amount of fuel off-gassing, helps you understand relativity to the box, sets an impression for everything else. A small volume of smoke from more than one opening of a LARGE building is significant.
Velocity (Speed and flow characteristic) = Pressure build-up. Only volume and heat can cause pressure. Volume-caused pressure will immediately slow down. Heat-caused pressure slows gradually. Turbulent smoke is heat-caused. Comparing velocities help you figure WHERE the actual fire is. Look for the fastest smoke from the most-resistive opening.
Density = Quality of Burning, potential for event - PERHAPS THE MOST IMPORTANT FACTOR FOR PREDICTING SEVERITY – the thicker the smoke, the more dangerous it is. Zero-visibility smoke has fuel continuity to the fire and can ignite with no warning to those within it. Zero-visibility smoke with high velocity is amazingly dangerous!
Color = Stage of heating and distance to fire. As a starting place, White is cooler, black is hotter. Carbon and hydrocarbons are STICKY and can be FILTERED – taking away blackness as smoke travels over distance or through cracks. White smoke should not be discarded! DIRTY WHITE smoke with velocity means a hot fire – but the smoke you see has traveled some distance. Thin, black smoke means “Flame Pushed.” Brown Smoke means unfinished wood is pyrolyizing.
REMEMBER THE TERM: “BLACK FIRE” Black fire = high-volume, turbulent velocity, super dense, and black smoke. It is a sure sign of an impending (delayed) flashover!
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STEP 2: WHAT is INFLUENCING THE KEY ATTRIBUTES?
Container – can change the meaning of volume, velocity, density, and color
Weather – hot/humid gives a narrow, defined column; hot/dry gives a cone shaped column; cold/humid causes the smoke to crash and hangout near; cold/dry causes the smoke to crash but disperse easily. Below freezing air temperatures can make black smoke look white within a few feet of the outside vent opening (moisture content of smoke condensing).
Firefighting Efforts – all four attributes should change: Volume increases; velocity surges then slows down; density immediately decreases; color goes to clean/pristine white. If this isn’t happening, the fire attack is inadequate. PPV fans can alter all the smoke attributes.
STEP 3: Determine the Rate of Change – Answer the Questions
Getting Better or Getting Worse? Seconds or minutes?
Reading Smoke Shortcuts
What You See What It Can Mean
Turbulent smoke Warning sign of impending flashover that fills a box Thick, black, fast Close to the seat of the fire, super hot smoke capable of instant ignition, maybe a vent-limited fire that needs air Thin, black, fast Flame-pushed smoke; Fire nearby that is well ventilated
Dirty white smoke Heat-pushed smoke that has traveled a distance or has had with velocity the carbon/hydrocarbon filtered (like smoke through a crack) Same color Deep-seated fire, possibly located well within a building or in (white/gray) and combustible voids and concealed spaces same velocity from multiple openings Low volume white Serious fire deep within smoke from more than one location of a large box Brown smoke Unfinished wood pyrolyizing (can support flame); usually a sign that a contents fire is transitioning into a structural fire; when coming from structural spaces of lightweight wood structures, a warning sign of collapse! Yellowish-gray Sulfur compounds = Warning sign of impending backdraft smoke from cracks or seams
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GROUP ACTIVITY: What Does the Smoke Say?
Specifically where is the fire?
How big or intense is the fire?
What’s Next? (where is the fire going and how fast - be specific)
Remember:
Practice doesn’t make perfect, PERFECT practice makes perfect!
Don’t be ARBITRARILY AGGRESSIVE – Be INTELLECTUALLY AGGRESSIVE!
PASS ON THIS INFORMATION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Call me if you want more info: Dave Dodson (303) 912-1201, [email protected]
The “Reading Smoke” PowerPoint is available as a free download at: www.firefighterclosecalls.com
Find videos at www.firevideo.com or www.firelinevideo.com or www.firestormvideos.com. You can also find fire video clips at www.firefighterclosecalls.com, www.youtube.com, or through a Google search using keywords “Flashover” or “Reading Smoke.”
Dave Dodson’s 3 volume “Reading Smoke” DVD training set is available for purchase through www.pennwellbooks.com.
Don’t just Be SAFE – Go out and Make it SAFE !
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