TACTICALTRIANGLE FIREBEHAVIOR BUILDING CONSTRUCTION TACTICAL DECISION CAPABILITIES AND LIMITATIONS
Science A branch of knowledge or study dealing with a body of facts or truths systematically arranged and showing the operation of general laws.
Fire Fighters that use scientific facts • Earn Credibility • Can Defend their Actions Legally • Teach to Referenced/Documented Standards and Practices • Can Protect Themselves • Are Fire Fighter’s that Think for Themselves
Scientific Testing Provides • Common standards used by manufacturers for design • Measurable limits and capabilities • Points of reference to base tactical and strategic decisions • Fire Fighting Facts that are referenced and documented • Facts for lawyers
Science = Life Measurable Documented Justifiable
FIRE BEHAVIOR A FOUNDATION BUILT ON SCIENCE
UNDERSTANDING OUR ENEMY GETS RID OF THE BOOGIE MAN
A BASE LINE PERSPECTIVE GETS US ALL ON THE SAME PAGE
FIRE BEHAVIOR SCIENTIFIC FACTS • Fire Triangle – Fuel, Air, Heat • ASTM E-119 Test • Standard Time Temperature Curve (1916) • Ordinary fuel load – Btu’s - configuration • Btu’s in a cubic ft. of air – rate? • Flame spread • Smoke expansion – Charles Law • Flammable Range of smoke (CO) • Temperature at the floor • Reading the heat in the smoke • Thermal Balance • Rate of Change
FIRE TRIANGLE/TETRAHEDRON Understanding the science within the fire triangle/tetrahedron builds your tactical & strategic perspective on a scientific foundation, that verifies your experience and the experience of others.
FUEL • Three States of Matter: • Solid • Liquid • Gas
FUEL • Two Categories: Hydrocarbon Based: • Gasoline • Diesel • Fuel Oil • Plastics, etc
FUEL Cellulose Based: • Wood • Paper • Cotton • Natural Fiber
COMMON FUELS • Most Common Fuels Contain: • Carbon • Hydrogen • Oxygen
SOLID FUELS • The Initiation of Combustion Requires Phase Conversion to a Gaseous State by Heating • Fuel Gases are Evolved from Solid Fuels by Pyrolysis • The Speed of Pyrolysis is Affected by it’s Arrangement and Surface Mass Ratio
SOLID FUELS • Ignition Temp. 451 Deg. F • Ordinary Combustibles- 8,000 btu’s per lb. • Hydrocarbon (Plastics)- 16,000 btu’s per lb.
Air - Ventilation • Fuel controlled fire, the growth is determined by the amount of available fuel with an abundant supply of air • When burning in the open or early stage of compartment fire, where there is excess air available
Air - Ventilation • Ventilation controlled fire, the growth is determined by the amount of available air • A ventilation controlled fire occurs when there is not enough air to burn the materials being pyrolyzed
Air – Ventilation - Profile • Based on ASTM- E119 tests • Ratio of ventilation opening to floor area involved • Ordinary Development =10% to 15% ventilation to floor area ratio • Accelerated Development = More than 15%ventilation to floor area ratio • Ventilation Controlled = Less than 10% ventilation to floor area ratio
THORTON’S RULE • The Heat of Combustion per kg of O2 Consumed is Nearly Constant for Most Organic Fuels, 13.1 kg per Gram of O2 Consumed • Most fires We Go to Are Ventilation Controlled • This Means that Hydrocarbon based Fuels and Cellulose based Fuels have About the Same (hrr) Heat Release Rate • Once the Fire is No Longer Ventilation Controlled, the Hydrocarbon Based Fuels can Release Almost 3 Times the (hrr) Energy as Cellulose based
LIQUID FUELS • Flammable Liquids Like Gasoline, Ignition Temp. Under 100 Deg. F • Combustible Liquids Like Diesel, Ignition Temp. Above 100 Deg. F • 125,000 to 140,000 btu’s per Gallon • Most Flammable and Combustible Liquids Will Float on Water as They Have a Lower Specific Gravity than Water • Polar Solvents and Alcohol Will Mix With Water
GAS FUELS • Compressed Gas Fuels like Propane and Natural Gas, or Carbon Monoxide and Hydrogen • Propane -2,500 btu’s per cu/ft • Natural Gas -1,100 btu’s per cu/ft • Carbon Monoxide – 323 btu’s per cu/ft • Hydrogen – 325 btu’s per cu/ft • Requires No Pre Heating to Ignite
British Thermal Units • BTU’s WE LOVE EM! • Quantifies heat release rate for building construction strength. • Quantifies heat release rate for fire development • Quantifies water • 1 BTU is the amount of heat required to raise a pound of water 1 degree fahrenheit from 60 degrees fahrenheit.
ASTM E-119 POINT “A” A Place to START!
ASTM - E119Methods of Fire Tests of Building Construction and Materials • Helps to build a SCIENTIFIC perspective for fuel loading and configuration • Still used today -Standard Time Temperature Test (since 1918) • Helps to build a SCIENTIFIC perspective for HEAT IN YOUR WORK PLACE! • Our battlefield the fire structure is built on this testing
Ordinary fuel load is 8,000 btu’s per pound,10 pounds per square foot.80,000 btu’s per square foot • 1 Hour Fire • Wood, • paper, • textiles 8,000 btu's / lb 10 lbs/sq ft l
The Box Minimum size for test specimens Floors and Roofs 160 squ. Ft. Partition and Walls are 380 squ. Ft. Length x Width x Height = Cubic Feet 8 x 10 x 8 = 640 cu. ft.
Furnace test replicates the wood crib test fuel load’s heat release rate of 8,000 btu’s per pound at 10 pounds per square foot. 80,000 btu’s per square foot for a 1 Hour Fire.
STANDARD TIME TEMPERATURE CURVE (1917-1918) Temperatures at Ceiling 5 minutes 1000 deg. F. • TP - ignition source 10 minutes 1300 deg. F. 15 minutes 1400 deg. F. 20 minutes 1460 deg. F. 25 minutes 1510 deg. F. 30 minutes 1550 deg. F. 45 minutes 1638 deg. F. • TP- wired glass 60 minutes 1700 deg. F. 1 hour 1700 deg. F. 80,000 btu’s/square foot 2 hour 1850 deg. F 3 hour 1920 deg. F. 4 hour 2000 deg. F. 8 hour 2300 deg. F.
ASTM E-119 • Pass/fail criteria are based upon the peak temperature attained at the back of the test article and/or whether or not the test article collapses or distorts in a fashion that allows hot gases to escape (and in the case of E119, whether the wall can withstand the pressure of a hose stream). • Wall & Floor Assemblies: 325 deg. F. at any one point or 250 deg. F. overall • FF Practical Tactical – non burning side touch. • Structural Elements Supporting the Load: 1200 deg. F. at any one point and 1000 deg. F. overall • FF Practical Tactical – water sheen.
Peak Development for Ordinary Fire is 4,8oo (Vito) Fully Developed 4,800 - 5,000 btu’s /squ. ft./min. 129 – 135 cfm FO BD Growth Decay
ASTM E-119 Test load vs. N.F.P.A. surveyed load 10 lbs/sq.ft. 5 lbs/sq.ft. Real World Half the Load!
What about plastics?16,000 btu’s per pound! • Remember half the load compared to the test load • Less Mass: plastic is stronger per pound than wood • Ventilation effect in structures • Incomplete combustion • What is the air flow rate? How much air does the fire need? How much water do you really need?
Factors that affect Fire Development • Surface to Mass Ratio • Location of the fuel (center , wall, corner) • Size, number, and arrangement of the vent openings • Volume of the box • Ceiling Height of the box 8’ • Target Fuels
Surface to Mass Ratio • The more air that reaches the surface of the fuel the higher the HRR. The lighter the fuel the faster the HRR.
Location of the Fire in the Box • Fires in the middle of the room entrains air and are cooler. • Fire against the wall is 50% higher HRR • Fire in the corner is 70% higher HRR • The walls reflect heat back to the fire
You & Your Environment • Volume of the box 8’x20’x8’=1,280 cu’ • In a room of a 160 square feet (8x20, 16x10) a fuel load of 16 square feet (4x4)at 10 lbs per square foot (2) upholstered chairs, That would fill the box with incomplete combustion. • Limited space for heat & conversion space • The same fire in Costco would be complete combustion and you would be able to walk right up to the fire. • Plenty of room for conversion and convected heat
Ceiling Height • 8’ ceilings - Residential Structures • Allow for horizontal spread of 40% of the heat of the fire by convection. (touch) • Heat is radiated to the other target fuels and the floor from the convected heat layer trapped below the ceiling • When convected gas ignites and can add an additional 40% of the fires heat by radiation (light) • In general, during a growth stage fire, when 500 degrees F. is reached at mid wall, zero visibility opposite wall from fire, and off gassing at the floor, flashover is possible.