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Fire I & II CH 4
Fire Dynamics
| Term | Definition |
|---|---|
| Common Oxidizers and their uses (5) | Calcium Hypochlorite (granular s) - pools chlor | chlorine (gas) - water purif | Ammonium Nitrate (granular s) - fertilizer | hydrogen Peroxide (liquid) - industrial bleach [pulp/paper/chemical mfg| Methyl Ethyl Ketone Peroxide - catalyst in plastics mfg |
| 7 types of Energy | chemical, mechanical, thermal, electrical, light, nuclear, sound |
| T o F All types of energy can change from one type to another. | True |
| Measurement of Energy in the International System of Units (SI) | Joules (J) .......quantity of heat required to change 1 gram of water by 1 degree Celsius = 4.2 Joules |
| Customary System measurement of energy | British Thermal Unit (BTU).... amount of heat required to raise 1 pound of water by 1 degree Farenheit |
| Comparison of Joules to BTU | 1055 J = 1 BTU |
| heat of combustion | the potential energy available for release in the combustion process |
| Types of Reactions that emit energy (2) | Endo and exothermic |
| Which type of reaction is Fire | Exothermic, it emits heat and sometimes light |
| What is an example of an endothermic reaction? | converting water from a liquid to a gas (steam) |
| T o F Fire is an example of a solid-phase combustion? | FALSE it is a gas-phase combustion |
| What is Off-gasing | when heat is transferred to a liquid or solid, the temperature of that substance rises and starts to convert to a gaseous state |
| What are the examples of off-gasing in solids and liquids? | pyrolysis, and vaporization |
| Piloted Ignition | most common, occurs when fuel + O2 encounters external heat source with sufficient heat or thermal energy to start the combustion reaction |
| Autoignition | occurs without external flame or spark, the fuels surface is heated to the point at which the combustions reaction occurs |
| AIT | Autoignition Temperature - the minimum temperature in which a fuel in the air must be heated in order to start self-sustained combustion |
| Which temperature point of a substance is higher, Piloted ignition temp or AIT? | AIT is always higher |
| What are the two modes of combustion? | NON-FLAMING - slow and lower temp producing a smoldering glow (burning charcoal) | FLAMING - |
| Which Fire model represents non-flaming combustion? | fire triangle |
| Which Fire model represents flaming combustion? | fire tetrahedron |
| Explain | ignition is where flaming combustion begins, the heat source pyrolizes a fuel creating fuel gases, which ignite when they mix with O2 , The fire is the pump, fresh O2 pumped in (inlet flow), and combustion products pump out (exhaust flow) |
| Entrained | referring to air being drawn in |
| Which has a higher density, the hot combustion products or the surrounding air? | the surrounding colder air, which is why the products of combustion sit on top and form layers |
| What is the product of incomplete combustion? | Smoke, when some of the fuel does not undergo a chemical conversion from its current form |
| Example of complete product combustion? | Methane results in heat, light, water vapor, and CO2 |
| 2 main types of fuels that fires involve? | carbon-based fuels (wood, cotton) | hydrocarbon fuels (plastics, synthetic fabrics) |
| Does an Oxygen deficient or Oxygen enriched atmosphere create more incomplete combustion? (smoke) | Oxygen deficient atmospheres create more incomplete combustion (less chemical reaction) |
| How is CO and CO2 created during a fire? | As the O2 is removed from the atmosphere through the chemical reaction, it combines with the combustion product of carbon |
| Asphyxiation | fatal level of O2 deficiency in the blood, can be caused by low O2 in the atmosphere AND/OR the concentrations of the products of combustion |
| 6 Common Products of Combustion | CO, Formaldehyde, Hydrogen Cyanide, Nitrogen Dioxide, Particulates, Sulfur Dioxide |
| Carbon Monoxide | CO (colorless, odorless, 0.2% is harmful) combines with hemoglobin 200x more effectively than O2, does not act on the body but excludes O2 from the blood resulting in hypoxia of the brain and tissues. |
| Formaldehyde | Formaldehyde (colorless gas pungent irritating odor, 50-100ppm can cause severe irritation, is a carcinogen |
| Hydrogen Cyanide | HCN (combustion from products of nitrogen) is 35% more toxic than CO, It's a colorless, toxic, and flammable liquid BELOW 79 F. Prevents the body from using O2, commonly found in smoke in concentrations lower than CO (less than 0.2%) |
| Nitrogen Dioxide | Reddish-brown gas or yellowish-brown liquid, highly toxic and corrosive |
| Particulates | small particles in the mouth, trachea, or lungs, eye irritation, respiratory distress |
| Sulfur Dioxide | Colorless gas with a choking or suffocation odor, toxic and corrosive and can irritate the eyes and mucous membranes |
| What two combustion materials need to incompletely combust to create HCN? | nitrogen and carbon |
| What materials produce HCN? 4 | natural fibers (wool, cotton and silk), resins (carbon fiber or fiberglass), synthetic polymers (nylon or polyester), synthetic rubber (neoprene, silicone, and latex) |
| Why is HCN 35x more toxix than CO? | It prevents the body from using O@ at the cellular level, can be inhaled, ingested, or absorbed, and then targets the heart and brain...it is a byproduct of the combustion of polyurethane foam (many household furnishings) |
| CO2 and CO, which is product or complete/incomplete combustion or organic materials (carbon containing)? | CO2 is complete combustion, CO is incomplete |
| Carbon Dioxide (CO2) | product of complete combustion of organic materials. its not toxic in the same manner as CO and HCN. It displaced the O2 and creates and O2 deficient atmospheres. CO2 acts as a respiratory stimulant and increases the RR |
| 3 examples of irritants in Smoke | hydrogen chloride, formaldehyde, and acrolein |
| Pressure | The force unit of area applied perpendicular to a surface. (kPa). Pressure in a fire compartment less thant 0.1 kPa can create movement. |
| Difference between Heat Release Rate and Temperature | temp is the average measurement kinetic energy in the particles. 1 candle vs 10 candles. 10 candles 10x greater heat release rate (kW). greater heat flux (kw per square meter) temp says safe to go in, heat transfer rate how long to stay in |
| Heat Flux | the energy flow involved in heat transfer rate. Measured by kW per square meter |
| T o F temperature is an accurate predictor or measurement of heat transfer | False |
| self heating | a form of oxidation, that increases temp without external heat, the material heats due to inability to dissipate energy as fast as it develops |
| spontaneous combustion and 3 requirements | material self heats to the point of AIT, due to 1) the materials insulation prevents energy from dissipating as fast as generated 2)reaches AIT 3) available air supply in and around material must be adequate to support combustion |
| 3 examples of spontaneous heating materials | Charcoal, Linseed oil-soaked rags, hay and manure |
| 3 Sources of Thermal Energy | Chemical, Mechanical, Electrical |
| 4 ways of Electrical Heating | resistance, overload or overcurrent, arcing, sparking |
| the 3 mechanisms of Heat Transfer | conduction, convection, radiation |
| What is the relationship of heat transfer rate and temperature differences of materials? | the greater the temperature difference, the greater the heat transfer rate |
| T o F Air is a good insulator? | True, it is the least able to conduct heat of most substances |
| Order these from least to most able to conduct Heat. Steel, gypsum board, copper, wood, concrete, air | air, wood, gypsum board, concrete, steel , copper |
| Lateral movement is due to ______. Vertical movement is due to _____. (convection) | ... pressure differences. the buoyancy of smoke and fire gases |
| T o F Radiation is disrupted by the air in the space between materials | False. convection and conduction are disrupted |
| What are synthetics made of | petroleum products |
| Power and the SI (Standard International) unit | the rate at which energy converts from one form to another, the watt; 1 watt = 1 joule per second (J/s) |
| Heat release rate and how it is measured | the energy released per unit of time as a fuel burns, kW or MW, directly relates to O2 consumption |
| Vapor Density | the density of gases in relation to air (1) |
| Specific Gravity | the ratio of the mass of a given volume of liquid compared to the mass of an equal volume of water the the same temperature. (water = 1) |
| vapor pressure | the pressure of vapors escaping a liquid exert. This pressure must be greater than atmospheric pressure in order for vaporization to occur. (liquids vaporize, solids pyrolyze) |
| Flash Point vs Fire Point | Flash Point is the min temp at which liquid gives off sufficient vapors to ignite but not sustain combustion, in the presence of a piloted ignition source. Fire Point is sustained combustion |
| Which type of liquid mixes with water? + 2 examples | Polar solvents, alcohols (ethanol, methanol) |
| Which type of liquid does not mix with water? 3 examples | Hydrocarbon fuels (gasoline, diesel, fuel oil) Specific gravity less than 1 |
| Wood begins to pyrolyze at temperatures _____ | Below 400 F, (which is lower than temp required for ignition of vapors) |
| 5 likely materials of insulation, exterior, and interior finish materials | polyvinyl chloride, polyethylene, polystyrene, polypropylene, polyurethane |
| What is the most common material in upholstered furniture? | Polyurethane Foam (PUF) |
| 4 Stages of wood burning | 1) < 392F, moisture + comb + noncomb mats released, insufficient heat for ignition, 2) 392-536F, majority of moisture released, charring begun, CO is primary compound, no ignition, 3) 536-932F rapid pyrolysis, ignition + charcoal 4) >932F Free Burning |
| 3 Stages of PUF | Polyurethane Foam 1) <392F PUF thermally degrades into comb gas and liquids 2) 392-536F liquid polyols vaporize into comb gases which can ignite 3) 536-932F pyrolysis at increased rate, PUF ignition at 698F, AI occurs between 797-833F, no char is formed |
| What is the primary consideration for how easily Solid fuels can ignite? | Surface - to - mass ratio |
| What is normal ambient temperature, and at what percentage of O2 concentration can materials burn. | 68F and 15% |
| T o F In compartment fires, the energy released is proportional to the amount of fuel. | FALSE, energy released is proportionate to the amount of O2 available |
| What is the temp range that wood pyrolyzed gas materials ignites, and the range that PUF gases and vaporized liquids can ignite? | Wood 536-932F, PUF ignition occurs at 698F |
| Temperature range at which AI of PUF? | autoignition of Polyurethane Foam occurs at 797-833 F |
| 02 Percentage in O2 deficient and 02 enriched atmospheres? | 19.5% ; 23.5% |
| One material that burns in O2 enriched atmosphere, what percentage, and examples of O2 enriched atmospheres? | Nomex at 31 % ; hospitals and healthcare facilities, industrial occupancies, and private homes with breathing equipment |
| LEL vs UEL | low % of O2 that makes vapors too lean to burn, and UEL is the % that is too rich to burn.....these points make up the Flammable (explosive) Range |
| List these flammable gases and liquids from least to most flammable and give their flammable ranges: ethanol, methanol, diesel, gasoline, CO, propane, methane | Diesel 1.3-6%, Gasoline 1.4 - 7.4%, Propane 2.1-9.5%, Ethanol 3.3-19%, Methane 5-15%, Methanol 6-35.5% |
| What two elements are formed during the oxidation of methane? and what 2 are formed after the combustion process | CO2 and H2O, CO and formaldehyde |
| What is the name of electrically charge, highly reactive parts of molecules | free radicals |
| What is the term referring to when an extinguishing agent, such as halon-replacement agent or dry chemical, is used and forms a stable product to interfere/terminate the combustion reaction? | Chemical Flame Inhibition |
| What are the 4 stages of fire development? | Incipient, growth, fully developed, decay |
| 3 key factors that control how the fire develops: | The fuel properties, the ventilation available, and heat conservation |
| What is the term for the flow of hot gases that rises vertically and then horizontally when met with an obstruction (ceiling)? | Ceiling Jet |
| Does open burning/free burning happen in a fuel limited or ventilation limited fire? | Fuel limited fire, think campfire, wooden pallets, or sofa in a large warehouse |
| When can you tell when an incipient fire is transitioning to the growth stage? | When the flames reach 2.5 feet |
| Unconfined fires draw air from all sides and the _________ of air cools the plume of hot gases, reducing flame length and vertical extension. | Entrainment |
| T o F When the fuel package is not in the middle of the room, the combustion zone expands vertically and a higher plume results. | TRUE |
| Flow Path | The space between the air intake and the exhaust outlet |
| This occurs when the ceiling jet reaches the outer walls. | Thermal Layering |
| Immediate indicator of flashover? | Isolated or intermittent flames |
| 2 Events of Rapid Fire Development | Flashover and Backdraft |
| Flashover | All combustible materials and fuel gases in a compartment ignite simultaneously, in the growth stage but can be in the fully developed stage due to change in ventilation. Min of 1100F goes from two-layer to single-layer mixed condition of hot gases |
| Significant indicator of flashover | rollover |
| 4 elements of flashover | Transition in fire development (growth to fully developed), rapidity, compartment, and pyrolysis of all exposed fuel surfaces |
| Two interrelated factors that determine whether a compartment will progress to flashover? | Sufficient fuel/heat release rate, ventilation |
| What is the AI temp of CO? | 1100F |
| Unit to measure heat flux | kW/m 2 |
| During rollover conditions, at the floor level (start of flashover) the heat flux is approximately ___ kW/m2. | 20 |
| Heat flux range of flashover? | 60kW/m 2 - 200 kW/m 2 |
| According to NIST testing in 2013, face pieces will melt after 5 mins of exposure to a heat flux of ______ | 15 kW/m 2 |
| Flashover Indicators (5) | Building, Smoke, Heat, Flame, Neutral Plane |
| Flashover Building Indicators (4) | Interior configuration, fuel load, ventilation, thermal properties |
| Flashover Smoke Indicators (5) | Rapidly increasing volume, turbulence, darkening color, optical density, and lowering of the hot gas layer and/or neutral plane |
| Flashover Heat Indicators (3) | Rapidly increasing temp in compartment, pyrolysis of contents located away from the fire, or hot surfaces |
| Flashover Flame Indicators (2) | Isolated flames, rollover in the hot gas layers or near the ceiling |
| Neutral Plane Indicators (High, Mid-level, Low) | High – early stages of development, or fire in above level, tall ceilings can hide a fire that’s more developed. Mid-Level – not yet ventilated, flashover approaching Low – fire may reach backdraft conditions, fire may be below |
| When the ventilation-limited compartment fills with flammable smoke and other gases, an introduction of new ventilation can cause explosively rapid combustion in a room, void space, or entire building | Backdraft |
| Backdraft | When the ventilation-limited compartment fills with flammable smoke and other gases, an introduction of new ventilation can cause explosively rapid combustion in a room, void space, or entire building |
| T o F Backdraft can only occur with a creation of a horizontal opening. | FALSE Backdraft can occur with both a horizontal and vertical opening. |
| Backdraft Indicators | Building, smoke, air flow, heat, flame |
| Backdraft Building Indicators (5) | Interior config, fuel load, thermal properties, amount of trapped fuel gases, and ventilation |
| Backdraft Smoke Indicators (2) | Pulsing smoke movement around small openings, smoke stained windows |
| Backdraft Air Flow Indicators (1) | High velocity air intake |
| Backdraft Heat Indicators (2) | High heat, crackling or breaking sounds |
| Backdraft Flame indicators (1) | Little or no visible flame |
Created by:
jon.kowalski