CFBT Glossary

This glossary provides structural firefighters and compartment fire behavior training (CFBT) instructors with a single source for fire behavior and CFBT terminology. For convenience, this glossary is divided alphabetically into sections.

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Glossary Information

This glossary is compiled and maintained by CFBT-US, LLC.


This glossary will help improve communication between CFBT-US instructors and students. As such, terminology used in CFBT-US courses, presentations, and publications will be consistent with this glossary. By providing a centralized, single source for fire behavior and CFBT terminology, it is hoped that this glossary will also promote consistency in terminology in the larger fire service community.


In order to provide the most up-to-date information, this glossary will be maintained on the CFBT-US web site. In addition, a downloadable electronic version of the glossary is also available in PDF format.

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Download the CFBT Glossary in PDF format.

Development & Maintenance

This glossary is intended to be a living document. Terms and definitions will be added or updated on an ongoing and regular basis. In order to maximize consistency and broad applicability, definitions will be determined and validated based on the following general hierarchy:

  1. International Standards Organization (ISO)
  2. National consensus standards organizations (e.g., NFPA, FPA)
  3. International or national professional associations (e.g., IFE, SFPE)
  4. Recognized texts (e.g., Enclosure Fire Dynamics, An Introduction to Fire Dynamics, Enclosure Fires, Fire Ventilation, Water and Other Extinguishing Agents.

In the inevitable conflict between sources, terminology and definitions will be submitted to the Institution of Fire Engineers (IFE) International Compartment Firefighting - Special Interest Group (SIG) for clarification and validation.

As an ongoing work in progress, comments or discussion will be provided in italic text following definitions that are particularly problematic, unclear, or inconsistent across standard references. It is the intent of this commentary to stimulate discussion within the fire behavior community to bring additional clarity and consistency to these terms.

Recommendations for additions, deletions, or revisions to the glossary should be submitted to CFBT-US Chief Instructor Ed Hartin, MS, EFO, MIFireE, CFO.

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3D Firefighting
3D firefighting is a concept that emphasizes the three-dimensional nature of the compartment fire environment and threats to firefighter safety. 3D concepts focus in particular on the hazard presented by unburned pyrolizate and flammable products of incomplete combustion present in smoke. 3D firefighting is grounded in an understanding of fire behavior and taking a proactive approach to controlling hazards in the fire environment.(3) This process includes:
  • Increased situational awareness through ongoing size-up of key fire behavior indicators from both the exterior and interior of the building;
  • Dynamic assessment of the risk associated with specific strategies and tactics on an ongoing basis;
  • Proactive control of hazards presented by unburned pyrolizate and flammable products of incomplete combustion present in smoke; and
  • Control of both smoke and air through effective ventilation strategies integrated with fire control.
3D Gas Cooling
See Gas Cooling
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Absolute Temperature
A temperature measured in Kelvins (K) or Rankines (R). (NFPA 921, 2008, 3.3.1*)
Temperature measured relative to absolute zero
Absolute Zero
The temperature at which all classical molecular motion stops, equal to 0 Kelvin or -273.15° Celsius
Absolute zero is defined as precisely 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale, and −273.15° on the Celsius (centigrade) scale. Absolute zero is also precisely equivalent to 0 °R on the Rankine scale (also a thermodynamic temperature scale), and −459.67 degrees on the Fahrenheit scale (Wikipidia)
Acute Toxicity
Toxicity that causes rapidly occurring toxic effects (ISO 13943, 2008, 4.5). Also see toxic potency.
A suspension of fine solid particles or liquid droplets in a gas (Wikipidia). Smoke would be one example of an aerosol.
Within the context of fireground operations, accountability provides a mechanism to track the following information throughout the incident:
  • Who is operating at the incident and who reports to individual supervisors (resources and individuals)
  • Where resources and individual members are operating.
  • What tactical assignments resources have been given and what tasks individuals are performing.
  • When resources were assigned, how long they have been engaged in their current assignment, and how long they have been operating at the incident.
  • If resources are making progress towards completion of their current assignment.
Actual Cooling Capacity
The actual amount of energy absorbed by water applied for fire control. This is less than the Theoretical Cooling Capacity as water applied by hand held nozzles or fixed fire suppression systems not completely converted to steam.
Discussion: Estimates of the efficiency of hand held nozzles vary considerably based on their design (solid stream versus fog), specific stream characteristics (droplet size and velocity) and skill in application.
Air Track
Movement of air towards the fire and movement of hot, buoyant combustion products out of the compartment or structure (Grimwood, Hartin, McDonough, & Raffel, 2005). Air track is a component of the Building, Smoke, Air Track, Heat, and Flame (B-SAHF) fire behavior indicators scheme.
Air Track, Direction
Air track refers to the movement of both smoke and air. In a compartment, smoke generally moves away from the fire and air moves towards the fire due to gravity current. However, actual movement is influenced by openings, barriers, and compartment geometry. Air track is commonly assessed at openings where the direction can be out (smoke completely filling the opening and moving outward), in (air completely filling the opening and moving in), bi-directional (smoke out at the upper level of the opening and in a the lower level), or pulsing (alternating inward and outward movement or similar variation in a bi-directional air track). Also see bi-directional air track and pulsing air track.
Air Track Indicators
Key categories of air track indicators include the direction that smoke and air is moving, velocity, flow (turbulence), and wind. Air track may be observed at compartment or building openings and while operating on the interior of a building.
Air Track, Turbulence
Turbulence is an important air track indicator. Turbulence is related to velocity of air and smoke movement. Faster movement, restriction, and obstacles create turbulent flow. Turbulence results in increased mixing of smoke (fuel) and air which may precipitate extreme fire behavior such as backdraft.
Air Track, Velocity
Velocity is an important air track indicator. Increased temperature in an enclosure results in increased pressure (See Guy Lussac’s Law and Ideal Gas Law), pressure raises velocity through openings. For a given opening size, increased velocity is an indication of increasing temperature within a compartment.
Alarm Time
Time interval between ignition of a fire and activation of an alarm. The time of ignition can be known, e.g. in the case of a fire model or a fire test, or it may be assumed, e.g. it may be based upon an estimate working back from the time of detection. The basis on which the time of ignition is determined is always stated when the alarm time is specified. (ISO 13943, 2008, 4.11)
Someone’s or something’s surroundings, especially as they pertain to the local environment; for example, ambient air and ambient temperature. (NFPA 921, 2008, 3.3.4)
Mineral residue resulting from complete combustion (ISO 13943, 2008, 4.16)
Toxicant that causes hypoxia, which can result in central nervous system depression or cardiovascular effects. Loss of consciousness and ultimately death can occur. (ISO 13943, 2008, 4.17)
Atmospheric Pressure
Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere. The standard atmosphere (atm) is a unit of pressure and is defined as being equal to 101.325 kPa. The following non-standard units are equivalent: 760 mmHg (torr), 29.92 inHg, 14.696 PSI, 1013.25 millibars.
Attack Cell
A single level, one-compartment prop used in compartment fire behavior training. Attack cells typically have several doors (rear and side) and vents in the roof or side to establish the desired fire conditions required for training. Attack cells are typically constructed from 12 m (40’) steel shipping containers.
Exposure of, and extension of fire to the exterior of the building and/or upper floors by means of flames extending from building openings (e.g., doors and windows).
Ignition resulting from a rise of temperature without a separate ignition source. The ignition can be caused either by self-heating or by heating from an external source. In North America, “spontaneous ignition” is the preferred term used to designate ignition caused by self-heating. (ISO 13943, 2008, 4.18)
Initiation of combustion by heat but without a spark or flame. (NFPA 921, 2008, 3.3.12)
Discussion: Used in the context of structural fire behavior, the term auto-ignition is also used to describe ignition of pyrolysis products and unburned products of incomplete combustion that are above their ignition temperature when they come in contact with air (e.g., outside an extremely ventilation under-ventilated compartment).
Auto-Ignition Temperature
Minimum temperature at which auto-ignition is obtained in a fire test (ISO 13943, 2008, 4.19). The typical units are degrees Celsius (°C).
The lowest temperature at which a combustible material ignites in air without a spark or flame. (NFPA 921, 2008, 3.3.13)
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Rapid flaming combustion caused by the sudden introduction of air into a confined oxygen-deficient space that contains hot products of incomplete combustion. In some cases, these conditions can result in an explosion. (ISO 13943, 2008, 4.21)
A deflagration resulting from the sudden introduction of air into a confined space containing oxygen-deficient products of incomplete combustion. (NFPA 921, 2008, 3.3.14)
A phenomenon that occurs when a fire takes place in a confined area such as a sealed aircraft fuselage and burns undetected until most of the oxygen within is consumed. The heat continues to produce flammable gases, mostly in the form of carbon monoxide. These gases are heated above their ignition temperature and when a supply of oxygen is introduced, as when normal entry points are opened, the gases could ignite with explosive force (NFPA 404, 2008).
Discussion: The ISO definition is considerably more broad than that specified in NFPA 921 and as such would be inclusive of phenomena such as ventilation induced flashover as well deflagration resulting from introduction of air to an extremely ventilation controlled fire. The definition of backdraft in NFPA 402, Guide for Aircraft Rescue and Firefighting Operations illustrates the common misconception that carbon monoxide is the primary gas phase fuel in a backdraft. There is no scientific evidence that this is the case.
English spelling, see Backdraft
Bar (bar)
A measure of pressure that is approximately equal to one standard atmosphere. The bar is not an SI unit, but are accepted for use in the SI system and recognized by countries in the European Union. 1 bar = 100 kPa (14.5 psi).
Baseline Vital Signs
The first measurement of vital signs (e.g., pulse, blood pressure, respirations, temperature). In the context of CFBT, baseline vital signs refers to measurement of vital signs prior to the start of training.
Bending Flames
When flames in the plume reach the ceiling and transition to horizontal movement in the ceiling jet. Bending flames are an indication that the speed of fire development will increase rapidly with significant potential for rollover and transition through flashover to a fully developed fire (depending on fuel characteristics and ventilation profile).
Black Body
Form that completely absorbs any electromagnetic radiation falling upon it (ISO 13943, 2008, 4.23).
No electromagnetic radiation passes through a black body and none is reflected. If the black body is hot, these properties make it an ideal source of thermal radiation.
Black Fire
Presence of a large volume of turbulent, black, and extremely thick (optically dense) smoke at high temperature. While not an extreme fire behavior phenomena, these fire behavior indicators point to extremely ventilation controlled fire conditions and potential for a vent induced flashover or backdraft.
Discussion: This term is a non-scientific qualitative description based on specific smoke, air track, and heat indicators.
Boiling Point
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation. Evaporation is a surface phenomenon in which molecules located near the vapor/liquid surface escape into the vapor phase. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, resulting in the formation of vapor bubbles within the liquid. (Wikipidia)
British Thermal Unit (Btu)
The quantity of heat required to raise the temperature of one pound of water 1°F at the pressure of 1 atmosphere and temperature of 60°F; a British thermal unit is equal to 1055 joules, 1.055 kilojoules, and 252.15 calories. (NFPA 921, 2008, 3.3.19)
British Thermal Unit/Hour (Btu/hr)
Unit of power equal to 0.29 watts.
Mnemonic for a standardized method for organizing fire behavior indicators on the basis of Building, Smoke, Air Track, Heat, and Flame factors or characteristics.
Buddy Check
Check of personal protective equipment performed by one crew member for another prior to entering a hazardous environment.
Building Element
Integral part of a built environment. This includes floors, walls, beams, columns, doors, and penetrations, but does not include contents. (ISO 13943, 2008, 4.25)
Building Factors
Building design and construction can have a significant influence on fire behavior and structural performance under fire conditions. Key factors include construction, contents, size, ventilation profile, and fire protection systems.
Building Indictors
Building factors considered in within the context of B-SAHF assessment of fire conditions and potential fire behavior. See Building Factors.
Building Size
From a fire behavior perspective, building size encompasses a number of other factors. First is the absolute size of the building, length, width, and height. However, the extent of compartmentalization, variations in compartment size, number of stories, and ceiling height are also important size related considerations.
Built Environment
Building or other structure. This also includes tunnels, bridges and means of transportation, such as motor vehicles and marine vessels (ISO 13943, 2008, 4.26).
Buffer Zone
Safer areas of operation inside a burning building created by application of water in a fog pattern to cool and inert the hot gas layer. Gas cooling results in lower hot gas layer temperatures (reducing radiant heat flux) and adds thermal ballast to slow reheating of the gases and reduce potential for ignition of the gases overhead (Grimwood, Hartin, Raffel, McDonough, 2005)
Buoyant Plume
Convective updraft of fluid above a heat source (ISO 13943, 2008, 4.27). Also see fire plume or plume.
Buoyancy is an upward force on an object immersed in a fluid (i.e., liquid or gas). If the object is less dense than the fluid, the fluid will exert an upward force on the object. Objects that are less dense than the fluid are said to be buoyant. Hot smoke and entrained air is less dense than cooler, ambient temperature air, making the smoke buoyant.
Burning Rate
See Heat Release Rate (HRR). NFPA 921, 2008, 3.3.20)
This term is depreciated; see heat release rate (ISO 13943, 2008, 4.177)
Burning Regime
The dominant influence on fire development (fuel or ventilation). Compartment fires may be in the fuel or ventilation controlled burning regime. See Fuel Controlled Fire and Ventilation Controlled Fire.
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In fire modeling, the process of adjusting modeling parameters in a computational model for the purpose of improving agreement with experimental data (ISO 13943, 2008, 4.34)
The amount of heat necessary to raise 1 gram of water 1oC at 15oC; a calorie is 4.184 joules, and there are 252.15 calories in a British thermal unit (Btu). (NFPA 921, 2008, 3.3.21)
Calorific Potential
This term is depreciated; see heat of combustion (ISO 13943, 2008, 4.174).
Calorific Value
This term is depreciated; see heat of combustion (ISO 13943, 2008, 4.174)
Apparatus that measures heat [as in heat of combustion] (ISO 13943, 2008, 4.35).
Carboxyhemoglobin Saturation
Percentage of blood hemoglobin converted to carboxyhemoglobin from the reversible reaction with inhaled carbon monoxide (ISO 13943, 2008, 4.36)
Case Study
Rather than using samples and following a rigid protocol to examine limited number of variables, case study methods involve an in-depth, longitudinal examination of a single instance or event: a case. They provide a systematic way of looking at events, collecting data, analyzing information, and reporting the results. As a result the researcher may gain a sharpened understanding of why the instance happened as it did, and what might become important to look at more extensively in future research. (Wikipidia)
Case studies are also used as a teaching tool, where the case is presented as a problem to be solved (e.g., What happened? Why did it happen? What were the causal and contributing factors? How could it have been prevented?)
Ceiling Jet
Gas motion in a hot gas layer near a ceiling that is generated by the buoyancy of a fire plume that is impinging upon the ceiling (ISO 13943, 2008, 4.37)
A relatively thin layer of flowing hot gases that develops under a horizontal surface (e.g., ceiling) as a result of plume impingement and the flowing gas being forced to move horizontally. (NFPA 921, 2008, 3.3.23)
Ceiling Layer
A buoyant layer of hot gases and smoke produced by a fire in a compartment. (NFPA 921, 2008, 3.3.24).
Carbonaceous residue resulting from pyrolysis or incomplete combustion.(ISO 13943, 2008, 4.38)
Carbonaceous material that has been burned or pyrolized and has a blackened appearance. (NFPA 921, 2008, 3.3.25)
Char Blisters
Convex segments of carbonized material separated by cracks or crevasses that form on the surface of char, forming on materials such as wood as the result of pyrolysis or burning. (NFPA 921-2008, 3.3.26)
Chimney Effect
Upward movement of hot fire effluent caused by convection currents confined within an essentially vertical enclosure. This usually draws more air into the fire. (ISO 13943, 2008, 4.41)
solid agglomerate of residues formed by either complete combustion or incomplete combustion and which can result from complete or partial melting (ISO 13943, 2008, 4.42).
Capable of burning, generally in air under normal conditions of ambient temperature and pressure, unless otherwise specified; combustion can occur in cases where an oxidizer other than the oxygen in air is present (e.g., chlorine, fluorine, or chemicals containing oxygen in their structure). (NFPA 921, 2008, 3.3.28)
Combustible Liquid
Any liquid that has a closed-cup flash point at or above 37.8°C (100°F). (See also 3.3.70, Flammable Liquid.) (NFPA 921, 2008, 3.3.30)
Exothermic reaction of a substance with an oxidizing agent. Combustion generally emits fire effluent accompanied by flames and/or glowing. (ISO 13943, 2008, 4.46)
Combustion Efficiency
Ratio of the amount of heat release in incomplete combustion to the theoretical heat of complete combustion. Combustion efficiency can be calculated only for cases where complete combustion can be defined. Combustion efficiency is usually expressed as a percentage and is, therefore, dimensionless. (ISO 13943, 2008, 4.47)
Discussion: While combustion efficiency can only be calculated where complete combustion can be defined, the effect of increases and decreases in combustion efficiency based on variation in ventilation profile may be discussed qualitatively.
Combustion Product
Solid, liquid and gaseous material resulting from combustion. Combustion products can include fire effluent, ash, char, clinker and/or soot.(ISO 13943, 2008, 4.48)
Heat, gases, solid particulates, and liquid aerosols produced by burning. (NFPA 921, 2008, 3.3.31)
Compartment Fire
A fire which is confined within a room or similar enclosure within a building (Drysdale. 1998).
Discussion: The term compartment fire is commonly used to describe fires within buildings regardless of whether they involve a single compartment or multiple compartments.
Compartment Fire Behavior Training (CFBT)
Training in practical fire dynamics as applied to compartment fires. CFBT typically addresses combustion theory, fire development in compartments, extreme fire behavior, fire behavior indicators and situational assessment, and firefighting tactics related to fire control and ventilation.
In the built environment, the extent to which the interior volume of a building or other structure is subdivided into floors and compartments.
Complete Combustion
Combustion in which all the combustion products are fully oxidized. This means that, when the oxidizing agent is oxygen, all carbon is converted to carbon dioxide and all hydrogen is converted to water. If elements other than carbon, hydrogen and oxygen are present in the combustible material, those elements are converted to the most stable products in their standard states at 298 K. (ISO 13943, 2008, 4.50)
Mass per unit volume. For a fire effluent the typical units are grams per cubic meter (g/m3). For a toxic gas, concentration is usually expressed as a volume fraction at T =298 K and P =1 atm, with typical units of microlitres per litre (μL/L), which is equivalent to cm3/m3 or 10-6. The concentration of a gas at a temperature, T, and a pressure, P can be calculated from its volume fraction (assuming ideal gas behavior) by multiplying the volume fraction by the density of the gas at that temperature and pressure. (ISO 13943, 2008, 4.52)
Heat transfer to another body or within a body by direct contact. (NFPA 921, 2008, 3.3.32)
Transfer of heat by movement of a fluid (ISO 13943, 2008, 4.54)
Heat transfer by circulation within a medium such as a gas or a liquid. (NFPA 921, 2008, 3.3.33)
Convective Heat Flux
Heat flux caused by convection (ISO 13943, 2008, 4.55)
Critical Rate of Flow
The minimum flow rate required to achieve fire control. Critical rate of flow is influenced by heat release rate and the efficiency of the water application method.
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Combustion wave propagating at subsonic velocity. If within a gaseous medium, deflagration is the same as a flame. (ISO 13943, 2008, 4.62)
Propagation of a combustion zone at a velocity that is less than the speed of sound in the unreacted medium. (NFPA 921, 2008, 3.3.37)
Decay Stage
As the fuel is consumed, the energy release rate diminishes and thus the average gas temperature in the compartment declines. The fire may go from ventilation-controlled to fuel controlled (Karlsson & Quintiere, 2000).
State of fire development when fuel is consumed and energy release diminishes, and temperatures decrease. During this stage the fire goes from ventilation-controlled to fuel-controlled (IFSTA, 2008)
Also see Fire Decay
Discussion: Unlike the ISO definition of Fire Decay, these common definitions of the decay stage do not address diminishing heat release rate as a result of ventilation control. Examining the heat release rate curve of a fire which is significantly under-ventilated shows that heat release rate is reduced (unless the ventilation profile changes) as a result of limited oxygen, not consumption of fuel. Any fire that has a diminishing heat release rate is in decay. However, it is critical to recognize the cause, fuel limitation or oxygen limitation.
Delayed Flashover
An English translation from Swedish terminology developed by fire protection engineers Mats Rosander and Krister Giselsson. See Smoke Explosion
Demonstration Cell
A single or split level, one-compartment prop used in compartment fire behavior training. Demonstration cells typically have several doors (rear and side) and vents in the roof or side to establish the desired fire conditions required for training. However, they are often designed to be operated (in demonstration mode) with the rear doors fully open. Demonstration cells are typically constructed from 12 m (40’) steel shipping containers.
The weight of a substance per unit volume, usually specified at standard temperature and pressure. The density of water is approximately 1 gram per cubic centimeter.The density of air is approximately 1.275 grams per cubic meter. (NFPA 921, 2008, 3.3.38). Also see Optical Density.
Deterministic Model
Fire model that uses science-based mathematical expressions to produce the same result each time the method is used with the same set of input data values (ISO 13943, 2008, 4.67)
Reaction characterized by a shock wave propagating at a velocity greater than the local speed of sound in the unreacted material. (ISO 13943, 2008, 4.68)
Propagation of a combustion zone at a velocity that is greater than the speed of sound in the unreacted medium. (NFPA 921, 2008, 3.3.40)
Diffusion Flame
Flame in which combustion occurs in a zone where the fuel and the oxidizing agent mix, having been initially separate (ISO 13943, 2008, 4.69)
A flame in which fuel and air mix or diffuse together at the region of combustion. (NFPA 921, 2008, 3.3.41)
Direct Attack
Application of water directly onto burning solid fuel to cool the fuel surface and reduce pyrolysis to achieve extinguishment.
Direction, Air Track
See Air Track, Direction
Doll’s House
A small scale prop used to demonstrate fire development. Doll’s houses may be comprised of a single compartment or multiple-compartments. While frequently constructed of particle board, they may also be made of metal or other non-combustible materials.
Door Control
Doors may be controlled in either the closed or open position to manage air track. Maintaining the door in a closed (or substantially closed) position limits introduction of air to ventilation controlled fires and confines smoke spread. Control of the door in an open position, ensures ease of access and egress and may allow use of the doorway as an effective inlet (depending on the ventilation profile and ventilation tactics used).
Door Entry
Procedure used to minimize the risk of extreme fire behavior and control introduction of air to ventilation controlled fires when entering a building or compartment involved in fire. Elements of the door entry process involve size-up, dynamic risk assessment, door control, and gas cooling (as needed).
Duration of Flaming
Length of time for which flaming combustion persists under specified conditions. (ISO 13943, 2008, 4.71)
Dynamic Risk Assessment
Dynamic risk assessment is an ongoing process to identify and eliminate or mitigate hazards and reduce risk. This process consists of the following elements.
  1. Hazard Identification
  2. Risk Assessment
  3. Risk Control
  4. Risk Elimination
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Effective Heat of Combustion
Heat released from a burning test specimen in a given time interval divided by the mass lost from the test specimen in the same time period. It is the same as the net heat of combustion if all the test specimen is converted to volatile combustion products and if all the combustion products are fully oxidized. The typical units are kilojoules per gram (kJ⋅g-1). (ISO 13943, 2008, 4.74)
Empirical Formula
Chemical formula of a substance in which the relative numbers of atoms of each type are given. (ISO 13943, 2008, 4.76)
Ratio of the radiation emitted by a radiant source to the radiation that would be emitted by a black body radiant source at the same temperature. Emissivity is dimensionless. (ISO 13943, 2008, 4.75)
In the built environment, volume defined by bounding surfaces, which may have one or more openings (ISO 13943, 2008, 4.77)
Enclosure Fire
See Compartment Fire
The process of air or gases being drawn into a fire, plume, or jet. (NFPA 921, 2008, 3.3.45)
Equivalence Ratio>/dt>
Fuel/air ratio divided by the fuel/air ratio required for a stoichiometric mixture. Standard, dry air contains 20,95 % oxygen by volume. In practice, the oxygen concentration in entrained air can vary and a calculation of the equivalence ratio to a standard, dry air basis is required. The equivalence ratio is dimensionless.(ISO 13943, 2008, 4.81)
Evaporation is a surface phenomenon in which molecules located near the vapor/liquid surface escape into the vapor phase.. Below its boiling point, molecules below the surface of of a liquid do not have enough heat energy to transition to the gas phase. However, molecular movement causes individual molecules at the surface to achieve sufficient energy to make this transition Paraphrased from Wikipidia
Event Tree
Depiction of temporal, causal sequences of events, built around a single initiating condition. (ISO 13943, 2008, 4.85)
Exclusion Criteria
Vital sign (e.g. pulse and respiratory rate, blood pressure) values and medical history (e.g., active respiratory infection, diarrhea) that would preclude an individual from participating in physiologically stressful training activity. See medical monitoring.
Chemical reaction resulting in an abrupt expansion of gas which can result from a rapid oxidation or decomposition reaction, with or without an increase in temperature (ISO 13943, 2008, 4.87)
The sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure. These high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials. (NFPA 921, 2008, 3.3.46)
Exposed Surface
The side of a structural assembly or object that is directly exposed to the fire. (NFPA 921, 2008, 3.3.49)
Surface of a test specimen subjected to the heating conditions of a fire test. (ISO 13943, 2008, 4.88)
Extreme Fire Behavior
An inclusive term for rapid fire progression phenomena such as flashover, backdraft, smoke explosion, and flash fire.
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Fault Tree
Depiction of the logical dependencies of events on one another, built around a critical resulting event, which usually has an unacceptable level of consequence and may be described as a failure. (ISO 13943, 2008, 4.95)
process of combustion characterized by the emission of heat and fire effluent and usually accompanied by smoke, flame, glowing or a combination thereof (ISO 13943, 2008, 4.96).
A rapid oxidation process, which is a chemical reaction resulting in the evolution of light and heat in varying intensities. (NFPA 921, 2008 3.3.55)
Fire Analysis
The process of determining the origin, cause, development, responsibility, and, when required, a failure analysis of a fire or explosion. (NFPA 921, 2008, 3.3.56)
Fire Barrier
Separating element that exhibits fire integrity or fire stability or thermal insulation, or a combination thereof, for a period of time under specified conditions. (ISO 13943, 2008, 4.99)
Fire Behavior
Change in, or maintenance of, the physical and/or chemical properties of an item and/or structure exposed to fire. This concept covers both reaction to fire and fire resistance. Also see Fire Performance. However, in English, this term may also be used to describe the behavior of a fire.(ISO 13943, 2008, 4.100)
Fire Behavior Indicators
Visual, audible, or tactile indicators of current (or potential) fie behavior. Indicators may be organized using the B-SAHF scheme: Building, Smoke, Air Track, Heat, and Flame.
Fire Cause
The circumstances, conditions, or agencies that bring together a fuel, ignition source, and oxidizer (such as air or oxygen) resulting in a fire or a combustion explosion. (NFPA 921, 2008, 3.3.57)
Fire Decay
Stage of fire development after a fire has reached its maximum intensity and during which the heat release rate and the temperature of the fire are decreasing (ISO 13943, 2008, 4.104). See Also Decay Stage
Discussion: This definition recognizes that (compartment) fires may decreased in heat release rate and temperature as a result of fuel or ventilation limitations. This is considerably different than many common definitions of Decay Stage.
Fire Development
Fire Development Curve
Fire Dynamics
The detailed study of how chemistry, fire science, and the engineering disciplines of fluid mechanics and heat transfer interact to influence fire behavior. (NFPA 921, 2008, 3.3.58*)
Fire Effluent
Totality of gases and aerosols, including suspended particles, created by combustion or pyrolysis in a fire (ISO 13943, 2008, 4.105). Also see Smoke.
Fire-Effluent Decay Characteristic
Physical and/or chemical change in fire effluent (4.105) caused by ageing and transport. (ISO 13943, 2008, 4.106)
Fire-Effluent Transport
Movement of fire effluent from the location of a fire. (ISO 13943, 2008, 4.107)
Fire Gases
gaseous part of combustion product(s) (ISO 13943, 2008, 4.110). See also Fire Effluent.
Fire Gas Ignition
Ignition of accumulated unburned pyrolysis products and flammable products of incomplete combustion existing in or transported into a flammable state (Grimwood, Hartin, McDonough, & Raffel, 2005)
Fire Growth
Stage of fire development during which the heat release rate and the temperature of the fire are increasing (ISO 13943, 2008, 4.111). Also see Growth Stage.
Fire Growth Rate
Rate of change of the heat release rate. Some factors that affect the fire growth rate are exposure, geometry, flame spread, and fire barriers. (NFPA 130, 2007)
Fire Load
quantity of heat which can be released by the complete combustion of all the combustible materials in a volume, including the facings of all bounding surfaces. Fire load may be based on effective heat of combustion, gross heat of combustion, or net heat of combustion as required by the specifier. The typical units for fire load are kilojoules (kJ) or megajoules (MJ). (ISO 13943, 2008, 4.114)
Fire Load Density
fire load per unit area. The typical units are kilojoules per square metre (kJ/m2).(ISO 13943, 2008, 4.115)
Fire Model
Calculation method that describes a system or process related to fire development, including fire dynamics and the effects of fire. (ISO 13943, 2008, 4.116) See also Deterministic Model, Numerical Fire Model, Physical Fire Model and Probabilistic Model.
Fire Plume
buoyant gas stream and any materials transported within it, above a fire. (ISO 13943, 2008, 4.118). Also see Buoyant Plume.
Fire Scenario
Qualitative description of the course of a fire with respect to time, identifying key events that characterize the studied fire and differentiate it from other possible fires. It typically defines the ignition and fire growth processes, the fully developed fire stage, the fire decay stage, and the environment and systems that impact on the course of the fire. (ISO 13943, 2008, 4.129)
Fire Science
The body of knowledge concerning the study of fire and related subjects (such as combustion, flame, products of combustion, heat release, heat transfer, fire and explosion chemistry, fire and explosion dynamics, thermodynamics, kinetics, fluid mechanics, fire safety) and their interaction with people, structures, and the environment. (NFPA 921, 2008, 3.3.63*)
Fire Simulation
See fire model. (ISO 13943, 2008, 4.116)
Fire simulation may also be used to describe a photographic, video, or animated simulation used for training or evaluation purposes
Fire Spread
The movement of fire from one place to another. (NFPA 921, 2008, 3.3.64)
Fire Stream Effectiveness
Fire Stream Efficiency
Fire Test
Test that measures behavior of a fire or exposes an item to the effects of a fire. The results of a fire test can be used to quantify fire severity or determine the fire resistance or reaction to fire of the test specimen. (ISO 13943, 2008, 4.132)
Flaming Debris
Material separating from a burning item and continuing to flame during a fire or fire test. (ISO 13943, 2008, 4.149)
Flaming Droplets
Molten material separating from a burning item and continuing to flame during a fire or fire test. (ISO 13943, 2008, 4.150)
Capable of flaming combustion under specified conditions. (ISO 13943, 2008, 4.153)
Capable of burning with a flame. (NFPA 921, 2008, 3.3.68)
Flammable Liquid
A liquid that has a closed-cup flash point that is below 37.8°C (100°F) and a maximum vapor pressure of 2068 mm Hg (40 psia) at 37.8°C (100°F). (NFPA 921, 2008, 3.3.70)
Flammability (Flammable) Limits
Concentration(s) of fuel vapor in air above and below which propagation of a flame does not occur in the presence of an ignition source The concentrations are usually expressed as a volume fraction at a defined temperature and pressure and expressed as a percentage. (ISO 13943, 2008, 4.152) Also see lower flammability limit, upper flammability limit.
The upper or lower concentration limit at a specified temperature and pressure of a flammable gas or a vapor of an ignitible liquid and air, expressed as a percentage of fuel by volume that can be ignited. (NFPA 921, 2008, 3.3.69)
Flammable Range
The range of concentrations between the lower and upper flammable limits. [68, 2007] (NFPA 921, 2008, 3.3.71)
Rapid, self-sustaining, sub-sonic propagation of combustion (4.46) in a gaseous medium, usually with emission of light (ISO 13943, 2008, 4.133).
A body or stream of gaseous material involved in the combustion process and emitting radiant energy at specific wavelength bands determined by the combustion chemistry of the fuel. In most cases, some portion of the emitted radiant energy is visible to the human eye. [72, 2007] (NFPA 921, 2008, 3.3.65)
Flame Front
Boundary of flaming combustion at the surface of a material or propagating through a gaseous mixture. (ISO 13943, 2008, 4.136)
The leading edge of burning gases of a combustion reaction. NFPA 921, 2008, 3.3.66)
Flame Indicators
Flame Spread
Propagation of a flame front. (ISO 13943, 2008, 4.142)
Flame Types
Flames may be classified as pre-mixed or diffusion flames based on where the fuel and air mix and as laminar or turbulent the extent of turbulence during combustion. See Pre-Mixed Flames, Diffusion Flames.
The condition where unburned fuel (pyrolizate) from the originating fire has accumulated in the ceiling layer to a sufficient concentration (i.e., at or above the lower flammable limit) that it ignites and burns; can occur without ignition of, or prior to, the ignition of other fuels separate from the origin. (NFPA 921, 2008, 3.3.67)
Flaming Combustion
Combustion in the gaseous phase, usually with emission of light. (ISO 13943, 2008, 4.148)
Flash Fire
A fire that spreads rapidly through a diffuse fuel, such as dust, gas, or the vapors of an ignitible liquid, without the production of damaging pressure. (NFPA 921, 2008, 3.3.72)
Stage of fire transition to a state of total surface involvement in a fire of combustible materials within an enclosure' (ISO 13943, 2008, 4.156)
A transitional phase in the development of a compartment fire in which surfaces exposed to thermal radiation reach ignition temperature more or less simultaneously and fire spreads rapidly throughout the space resulting in full room involvement or total involvement of the compartment or enclosed area (NFPA 921-2007)
Discussion: This transition is often assumed to take place between the growth and fully developed stages. However, neither the ISO nor NFPA definition specifies this condition. In addition, while the NFPA definition indicates that this transition is extremely rapid (i.e., more or less simultaneously), the ISO definition does not describe the speed with which the transition to total surface involvement occurs.
Flow Rate
Substance which can react exothermically with an oxidizing agent. (ISO 13943, 2008, 4.161)
A material that will maintain combustion under specified environmental conditions. (NFPA 921, 2008, 3.3.76)
Fuel Controlled Fire
A fire in which the heat release rate and growth rate are controlled by the characteristics of the fuel, such as quantity and geometry, and in which adequate air for combustion is available. (NFPA 921, 2008, 3.3.79)
Fuel Gas
Natural gas, manufactured gas, LP-Gas, and similar gases commonly used for commercial or residential purposes such as heating, cooling, or cooking. (NFPA 921, 2008, 3.3.77)
Discussion: Note that this is different than gas phase fuel (which is not necessarily a gas used for commercial or residential purposes, but refers to any fuel in the gas phase).
Fuel-Lean Combustion
Combustion in which the equivalence ratio is less than unity. In well-ventilated fires, the fuel/air mixture is fuel-lean and complete combustion tends to occur. (ISO 13943, 2008, 4.162)
Fuel-Rich Combustion
Combustion in which the equivalence ratio is greater than unity. In ventilation-controlled fire(s), the fuel/air mixture is fuel-rich, and relatively high concentration(s) of pyrolysis products and incomplete combustion gases result. (ISO 13943, 2008, 4.163)
Fuel Load
The total quantity of combustible contents of a building, space, or fire area, including interior finish and trim, expressed in heat units or the equivalent weight in wood. (NFPA 921, 2008, 3.3.78)
Fully Developed
State of total involvement of combustible materials in a fire (ISO 13943, 2008, 4.164)
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The physical state of a substance that has no shape or volume of its own and will expand to take the shape and volume of the container or enclosure it occupies. (NFPA 921, 2008, 3.3.81)
Gas Cooling
Gas Phase
Gas Specific Gravity
See Vapor Density
Transform a solid and/or liquid material into a gaseous state (ISO 13943, 2008, 4.165).
Gravity Current
Gray Area
Growth Stage
DEFINITION Also see Fire Growth.
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A form of energy characterized by vibration of molecules and capable of initiating and supporting chemical changes and changes of state. (NFPA 921, 2008, 3.3.86*)
Heat Capacity
Amount of thermal energy required to raise the temperature of an object by one Kelvin (ISO 13943, 2008, 4.171) The typical units are joules per Kelvin (J/K). Also see specific heat capacity
Heat Flow Rate
Amount of thermal energy transferred per unit time (ISO 13943, 2008, 4.172). The typical units are watts (W).
Heat Flux
Amount of thermal energy emitted, transmitted or received per unit area and per unit time (ISO 13943, 2008, 4.173), The typical units are watts per square metre (w/m2).
The measure of the rate of heat transfer to a surface, expressed in kilowatts/m2, kilojoules/m2 sec, or Btu/ft2 sec. (NFPA 921, 2008, 3.3.88)
Heat Indicators
Heat of Combustion
Thermal energy produced by combustion of unit mass of a given substance (ISO 13943, 2008, 4.174). The typical units are kilojoules per gram (kJ/g) or megajoules per kilogram (MJ/kg) Also see effective heat of combustion, gross heat of combustion and net heat of combustion.
Heat Release
Thermal energy produced by combustion (ISO 13943, 2008, 4.176). The typical units are joules (J).
Heat Release Rate (HRR)
Rate of thermal energy production generated by combustion (ISO 13943, 2008, 4.177). The typical units are watts (W).
The rate at which heat energy is generated by burning. (NFPA 921, 2008, 3.3.90*)
Heat Transfer
Heating Curve for Water
Hot Gas Layer
See Ceiling Layer.
Hot Gas Layer Interface
Hot Rich Flashover
English translation from Swedish terminology developed by fire protection engineers Mats Rosander and Krister Giselsson. See Auto Ignition
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Initiation of combustion (ISO 13943, 2008, 4.187). Initiation of sustained flame (ISO 13943, 2008, 4.188).
The process of initiating self-sustained combustion. (NFPA 921, 2008, 3.3.95)
Ignition Temperature
Minimum temperature a substance should attain in order to ignite under specific test conditions. (NFPA 921, 2008, 3.3.97*)
Immediately Dangerous to Life and Health (IDLH)
Fire which is in the initial or beginning stage and which can be controlled or extinguished by portable fire extinguishers, Class II standpipe or small hose systems without the need for protective clothing or breathing apparatus (29 CFR 1910.155(c)(26))
Incomplete Combustion
Indirect Attack
International System of Units
Abbreviated SI (from the French Le Système International d'Unités). SI is the modern metric system of measurement. Long the language universally used in science, the SI has become the dominant language of international commerce and trade. For more information see NIST Reference on Constants, Units, and Uncertainty: International System of Units
Interior Structural Firefighting
The physical activity of fire suppression, rescue or both, inside of buildings or enclosed structures which are involved in a fire situation beyond the incipient stage. (See 29 CFR 1910.155)
Isolated Flames
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The preferred SI unit of heat, energy, or work. A joule is the heat produced when one ampere is passed through a resistance of one ohm for one second, or it is the work required to have a distance of one meter against a force of one newton. There are 4.184 joules in a calorie, and 1055 joules in a British thermal unit (Btu). A watt is a joule/second. (See also 3.3.19, British Thermal Unit (Btu), and 3.3.21, Calorie.) (NFPA 921, 2008, 3.3.105)
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Kilowatt (kW)
One thousand joules per second. Abbreviated kW. ADD A BIT MORE HERE
A measurement of energy release rate. (NFPA 921, 2008, 3.3.106)
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Latent Heat of Vaporization
Lean Flashover
English translation from Swedish terminology developed by fire protection engineers Mats Rosander and Krister Giselsson. See Rollover
Live Fire Training
Long Pulse
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Mass Fraction
The fraction of one substance (XA) with mass MA to the total mixture mass Mtot It is a way of expressing concentration in a dimensionless size. Multiplying by 100 obtains the mass percentage. The mass fraction of component in a solution is the ratio between the mass concentration of that component in solution PA (partial density of that component) and the density of solution P.
Medical Monitoring
Megawatt (MW)
Models of Combustion
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National Firefighter Near Miss Program
National Institute for Occupational Safety and Health (NIOSH)
National Institute of Standards and Technology (NIST)
Neutral Plane
The level at a compartment opening where the difference in pressure exerted by expansion and buoyancy of hot smoke flowing out of the opening and the inward pressure of cooler, ambient temperature air flowing in through the opening is equal (Karlsson & Quintiere, 2000)
Numerical Fire Model
Mathematical representation of one or more of different interconnected phenomena governing the development of a fire. (ISO 13943, 2008, 4.242)
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Optical Density of Smoke
Measure of the attenuation of a light beam passing through smoke expressed as the logarithm to the base 10 of the opacity of smoke (ISO 13943, 2008, 4.245) The optical density of smoke is dimensionless.
Optical density is also used as a qualitative descriptor on the fireground
Optimum Rate of Flow
Chemical reaction in which the proportion of oxygen or other electronegative element in a substance is increased. In chemistry, the term has the broader meaning of a process that involves the loss of an electron or electrons from an atom, molecule or ion. (ISO 13943, 2008, 4.246)
Oxygen Consumption Principle
Proportional relationship between the mass of oxygen consumed during combustion and the heat released (ISO 13943, 2008, 4.248). A value of 13,1 kJ/g is commonly used. Also see Thornton's Rule.
Oxygen Deficiency
Insufficiency of oxygen to support combustion. (NFPA 921, 2008, 3.3.118) Also see Ventilation-Controlled Fire.
An atmosphere with an oxygen content below 19.5% by volume (29 CFR 1910.134(b))
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Passive Agents
Peak Heat Release Rate
Phase Change
Physical Fire Model
Laboratory process, including the apparatus, the environment and the fire test procedure intended to represent a certain phase of a fire. (ISO 13943, 2008, 4.252
Piloted Ignition
Ignition of combustible gases or vapors by a secondary source of energy such as a flame, spark, electrical arc or glowing wire (ISO 13943, 2008, 4.253)
See fire plume (ISO 13943, 2008, 4.118)
The column of hot gases, flames, and smoke rising above a fire; also called convection column, thermal updraft, or thermal column. (NFPA 921, 2008, 3.3.121)
Post-Flashover Fire
A fully developed fire or a fire in the decay stage which previously transitioned through flashover.
Pre-Flashover Fire
Fire in the incipient or growth stage, or which has become ventilation controlled to the extent to preclude reaching flashover (without a change in the ventilation profile).
Premixed Flame
Flame in which combustion occurs in an intimate mixture of fuel and oxidizing agent (ISO 13943, 2008, 4.260)
A flame for which the fuel and oxidizer are mixed prior to combustion, as in a laboratory Bunsen burner or a gas cooking range; propagation of the flame is governed by the interaction between flow rate, transport processes, and chemical reaction. (NFPA 921, 2008, 3.3.123)
Probabilistic Model
Fire model that treats phenomena as a series of sequential events or states, with mathematical rules to govern the transitions from one event to another and with probabilities assigned to each transfer point. An example of a transition is that of ignition becoming sustained combustion. (ISO 13943, 2008, 4.265)
Product(s) of Combustion
See Combustion Product (ISO 13943, 2008, 4.48)
See Combustion Products (NFPA 921, 2008, 3.3.125)
Pulsing Air Track
Product of decomposition through heat; a product of a chemical change caused by heating. (NFPA 921, 2008, 3.3.128)
Chemical decomposition of a substance by the action of heat Pyrolysis is often used to refer to a stage of fire before flaming combustion has begun.In fire science, no assumption is made about the presence or absence of oxygen. (ISO 13943, 2008, 4.267)
The chemical decomposition of a compound into one or more other substances by heat alone; pyrolysis often precedes combustion. (NFPA 921, 2008, 3.3.129)
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Radiant Heat
Heat energy carried by electromagnetic waves that are longer than light waves and shorter than radio waves; radiant heat (electromagnetic radiation) increases the sensible temperature of any substance capable of absorbing the radiation, especially solid and opaque objects. (NFPA 921, 2008, 3.3.131)
Radiant Heat Flux
Power per unit area emitted, transferred or received in the form of heat radiation. (ISO 13943, 2008, 4.270) The typical units are kilowatts per square metre (kW/m2).
[In thermodynamics,] heat transfer by way of electromagnetic energy NFPA 921, 2008, 3.3.132).
Radiative Heat Transfer
Transmission of heat by electromagnetic radiation (ISO 13943, 2008, 4.271)
Rapid Fire Progress
Rate of Heat Release
See Heat Release Rate (HRR). (NFPA 921, 2008, 3.3.133)
Required Fire Flow
Rich Flashover
English translation from Swedish terminology developed by fire protection engineers Mats Rosander and Krister Giselsson. See Backdraft
See Flameover. (NFPA 921, 2008, 3.3.137)
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Safe Zone
Safety Briefing
Scientific Method
The systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of a hypothesis. (NFPA 921, 2008, 3.3.139)
Short Pulse
Extremely brief application of water in a fog pattern. Short pulses are typically used to cool hot gas layer. With short pulses, the angle of the fog cone is dependent on the compartment configuration, nozzle type, and conditions. Pattern should maximize the amount of water vaporized in the hot gas layer and minimize water reaching compartment linings (i.e., ceiling and walls).
Small Scale Fire Test
fire test performed on a test specimen of small dimensions. A fire test performed on a test specimen of which the maximum dimension is less than 1 m is usually called a small-scale fire test. (ISO 13943, 2008, 4.293)
Visible part of fire effluent (ISO 13943, 2008, 4.294).
The airborne solid and liquid particulates and gases evolved when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass. [318, 2006] (NFPA 921, 2008, 3.3.148)
Smoke Condensate
The condensed residue of suspended vapors and liquid products of incomplete combustion. (NFPA 921, 2008, 3.3.149)
Smoke Explosion
See 3.3.14, Backdraft. (NFPA 921, 2008, 3.3.150)
When unburnt gases from an under-ventilated fire flow through leakages into a closed space connected to the fire room, the gases there can mix very well with air to form a combustible gas mixture. A small spark is then enough to cause a smoke gas explosion (Karlsson & Quintiere, 2000)
A smoke gas explosion results from ignition of a confined mass of smoke gases and air that fall within the flammable range. This may result in a significant increase in pressure within the compartment (parapaphrased from Bengtsson, 2001).
Discussion: In the past, the terms smoke explosion and backdraft were frequently used synonymously (and still used this way within NFPA 921). However, smoke explosion is a substantively different phenomenon as evidenced by the definitions provided by Karlsson & Quintiere (2000) and Bengtsson (2001). Drysdale (1998) also discusses this phenomena, and while not providing a definition per se, delineates the difference between smoke explosion and backdraft as different phenomena.
Smoke Indicators
Smoke Logging
Complete filling of a compartment or compartments with smoke. This may occur as the hot gas layer increases in depth from ceiling to floor or as a result cooling smoke becoming less buoyant and sinking.
Combustion without flame, usually with incandescence and smoke. (NFPA 921, 2008, 3.3.151) Also see Smoldering Combustion.
Smoldering Combustion
combustion of a material without flame and without visible light. Smoldering combustion is generally evidenced by an increase in temperature and/or by fire effluent. (ISO 13943, 2008, 4.297)
Solid Stream
A stream of water produced by a smooth bore nozzle. Note that this is different than a straight stream formed by a combination nozzle which is comprised of tightly grouped droplets.
Particulate matter produced and deposited during or after combustion. Soot usually consists of finely divided particles, mainly carbon, produced by the incomplete combustion of organic materials. (ISO 13943, 2008, 4.299)
Black particles of carbon produced in a flame. (NFPA 921, 2008, 3.3.152)
Chipping or pitting of concrete or masonry surfaces. (NFPA 921, 2008, 3.3.153)
Incandescent particle (ISO 13943, 2008, 4.300)
Luminous discharge resulting from the dielectric breakdown of a gas between two electrodes (ISO 13943, 2008, 4.301).
A moving particle of solid material that emits radiant energy due either to its temperature or the process of combustion on its surface. [654, 2006] (NFPA 921, 2008, 3.3.154)
Specific Gravity
The ratio of the average molecular weight of a given volume of liquid or solid to the average molecular weight of an equal volume of water at the same temperature and pressure. (NFPA 921, 2008, 3.3.156)
Specific Heat Capacity
Heat capacity per unit mass. (ISO 13943, 2008, 4.303) The typical units are joules per gram per Kelvin (J/g/K).
Spontaneous Heating
Process whereby a material increases in temperature without drawing heat from its surroundings. (NFPA 921, 2008, 3.3.158*)
Spontaneous Ignition
Initiation of combustion of a material by an internal chemical or biological reaction that has produced sufficient heat to ignite the material. (NFPA 921, 2008, 3.3.159)
See auto-ignition (ISO 13943, 2008, 4.18)
Spontaneous Ignition Temperature
See Auto-Ignition Temperature (ISO 13943, 2008, 4.19)
Step Event
Sudden change in heat release rate where the heat release rate of far ire reached during the change is sustained. Flashover would be an example of a step event. (Grimwood, Hartin, McDonough, & Raffel, 2005)
Stoichiometric Mixture
Mixture of chemical reactants having proportions in accordance with the equation for a specified chemical reaction (ISO 13943, 2008, 4.310)
Straight Stream
A stream of water produced by a combination nozzle by adjusting the angle of the fog cone to produce a straight stream. Note that this is different than a solid stream produced by a smooth bore nozzle as it is comprised of tightly grouped, small droplets.
Surface Cooling
Application of water to a solid surface to reduce its temperature. Surface cooling is used to reduce pyrolysis and achieve extinguishment or to prevent ignition of combustible surfaces subjected to heat flux.
Suppression System
System designed for the active stabilization, reduction or elimination of flame spread or heat release or smoke production (ISO 13943, 2008, 4.315)
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Tactical Anti-Ventilation
Planned and systematic confinement of heat, smoke, and fire gases and exclusion of fresh air.
Discussion: This tactic is more commonly associated with confinement in the United States. However, it is useful to conceptualize the influence of these tactics on fire behavior in conjunction with changes to the ventilation profile.
Tactical Rate of Flow
The flow rate required for effective and efficient tactical operations based on current and potential heat release rate. Estimation of tactical rate of flow is generally based on current and projected extent of involvement.
Discussion: There are a number of different methods for estimating tactical rate of flow (e.g., Iowa, National Fire Academy (NFA), Grimwood), each having slightly different assumptions and application.
Tactical Ventilation
Planned and systematic removal of heat, smoke, and fire gases, and their replacement with fresh air.
Discussion: In many fire service texts, this definition was (and continues to be) used to describe Ventilation. However, recognizing that ventilation is involves exchange of air inside a building with that outside in buildings that are not on fire and that this is a significant factor in fire development, it is best to differentiate between ventilation, changes to the ventilation profile that result from human action or fire effects (unplanned ventilation) and ventilation that is purposeful and part of the incident action plan (tactical ventilation).
On the smallest scale, temperature is defined as the average energy of microscopic motions (e.g., change in position, vibration, and rotation) of a single particle in the system. On a larger scale, temperature is the unique physical property that determines the direction of heat flow between two objects placed in thermal contact. If no heat flow occurs, the two objects have the same temperature; otherwise heat flows from the hotter object to the colder object.
The degree of sensible heat of a body as measured by a thermometer or similar instrument. (NFPA 921, 2008, 3.3.162*)
Temperature Check
A short pulse applied into the hot gas layer to determine relative temperature. The more water that is converted to steam (and does not return), the higher the temperature of the gases. Note that the effectiveness of this technique is dependent on the size of the water droplets produced by the nozzle (large droplets will not vaporize as readily and will tend to either vaporize on contact with compartment linings or drop back out of the hot gas layer.
Theoretical Cooling Capacity
The amount of energy required to raise a given mass of water to its boiling point of 100o C and completely vaporize it into steam. For example, raising 1 kg of water from 20o C to 100o C requires 0.3 MJ of energy. Vaporizing 1 kg of water into steam at 100o C requires 2.6 MJ of energy. This results in a theoretical cooling capacity of 2.6 MJ/kg
Thermal Balance
See Thermal Layering
Thermal Ballast
Thermal Column
See Plume. (NFPA 921, 2008, 3.3.163)
Thermal Conductivity
Parameter related to the rate at which heat flows through a material. The thermal conductivity, k, is equal to (Q·d )/(A·t) , where Q is the amount of heat that flows in time, t, through a material of thickness, d, and cross-sectional area, A, and which has a temperature difference, ?, across it, and where no heat is exchanged with the surroundings. (ISO 13943, 2008, 4.323) The typical units are watts per metre per Kelvin (W/m/K).
Thermal Decomposition
Process whereby the action of heat or elevated temperature on an item causes changes to the chemical composition. This is different from thermal degradation. (ISO 13943, 2008, 4.324)
Thermal Degradation
process whereby the action of heat or elevated temperature on an item causes a deterioration of one or more properties. Properties may be, for example, physical, mechanical or electrical. This is different from thermal decomposition.(ISO 13943, 2008, 4.325)
Thermal Expansion
The increase in length, volume, or superficial area of a body with rise in temperature. (NFPA 921, 2008, 3.3.164*)
Thermal Inertia
Product of thermal conductivity, density and specific heat capacity. When a material is exposed to a heat flux, the rate of increase of surface temperature depends strongly on the value of the thermal inertia of the material. The surface temperature of a material with a low thermal inertia rises relatively quickly when it is heated, and vice versa. (ISO 13943, 2008, 4.327) The typical units are joules squared per second per metre to the fourth power per Kelvin squared (J2/s/m4/K2).
The properties of a material that characterize its rate of surface temperature rise when exposed to heat; related to the product of the material’s thermal conductivity (k), its density (P), and its heat capacity (c). (NFPA 921, 2008, 3.3.165)
Thermal Layering
Development of a hot gas layer at the ceiling with cooler air below due to the buoyancy of hot smoke, fire gases, and entrained air. The compartment fire environment is often described with a two zone model based on the concept of thermal layering. However, the actual fire environment is considerably more complex, with variations in gas temperature based convection currents, turbulence, etc.
Thermal Radiation
Transfer of thermal energy by electromagnetic waves (ISO 13943, 2008, 4.330)
Thermal Runaway
In ventilation controlled fire, the point at which heat release rate exceeds energy lost through convection of hot gases through ventilation openings. Thermal runaway results in increasing compartment temperature and may lead to ventilation induced flashover. (paraphrased from Grimwood, Hartin, McDonough, & Raffel, 2005)
Thermal Thickness
Thermally Thick Solid Behavior
Negligible temperature rise on one face of a solid while heat flux is applied to the opposite face. This behavior depends on the exposure time, the level of heat flux, and material properties of the solid. (ISO 13943, 2008, 4.332)
Thermally Thin
Thermally Thin Solid Behavior
Negligible temperature gradient within a solid while heat flux is applied. This behavior depends on the exposure time, the level of heat flux, and material properties of the solid. (ISO 13943, 2008, 4.333)
Thornton's Rule
ADD A BIT HERE See Oxygen Consumption Principle
Time-Temperature Curve
Standardized time-related variation of temperature prescribed in a specified way during a standard fire resistance test (ISO 13943, 2008, 4.321)
Total Heat Flux
Sum of convective heat flux and radiant heat flux (ISO 13943, 2008, 4.334)
Transient Event
Sudden change of the heat release rate when the heat release rate normally returns to approximately its original value. (Grimwood, Hartin, McDonough, & Raffel, 2005)
Turbulence, Air Track
See Air Track, Turbulence
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Unpiloted ignition
See auto-ignition
Unplanned Ventilation
Upper Flammability Limit
maximum concentration of fuel vapour in air above which propagation of a flame will not occur in the presence of an ignition source. The concentration is usually expressed as a volume fraction at a defined temperature and pressure, and expressed as a percentage. (ISO 13943, 2008, 4.350)
Upper Layer
See Ceiling Layer (NFPA 921, 2008, 3.3.171)
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The gas phase of a substance, particularly of those that are normally liquids or solids at ordinary temperatures. Also see Gas (NFPA 921, 2008, 3.3.172)
Vapor Density
The ratio of the average molecular weight of a given volume of gas or vapor to the average molecular weight of an equal volume of air at the same temperature and pressure. (NFPA 921, 2008, 3.3.155)
Velocity, Air Track
See Air Track, Velocity
Circulation of air in any space by natural wind or convection or by fans blowing air into or exhausting air out of a building; a fire-fighting operation of removing smoke and heat from the structure by opening windows and doors or making holes in the roof. (NFPA 921, 2008, 3.3.175)
Ventilation Controlled Fire
A fire in which the heat release rate or growth is controlled by the amount of air available to the fire. (NFPA 921, 2008, 3.3.176)
Ventilation Induced Flashover
Thermal runaway and rapid transition to a fully developed fire resulting from an increase in ventilation to a ventilation controlled fire.
Discussion: Note the similarity in initiating event (increased ventilation) to backdraft. While not delineated in the definitions for these phenomena, distinguishing factors include the speed of reaction and the mass fraction of fuel in the gas phase present in the compartment. Backdraft involves combustion of fuel already in the gas phase to a greater extent than ventilation induced flashover.
Ventilation Profile
Maximum distance at which an object of defined size, brightness and contrast can be seen and recognized (ISO 13943, 2008, 4.351).
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Water Fog
Unit of power, or rate of work, equal to one joule per second, or the rate of work represented by a current of one ampere under the potential of one volt. (NFPA 921, 2008, 3.3.179)
Window Cell
A single level, one-compartment prop used in compartment fire behavior training to demonstrate fire development, flashover, and backdraft. Window cells typically have at least one split door that may be used to simulate a door or window, but may have additional doors or windows.. Window cells are typically constructed from 6 m (20) steel shipping containers.
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