Free CFEI Exam Flashcards

Fuel, oxygen, heat, and an uninhibited chemical chain reaction — all four must be present for flaming combustion; removing any one extinguishes the fire. NFPA 921 distinguishes this four-sided model from the older fire triangle (fuel-heat-oxygen), which omits the chain reaction needed to sustain flaming combustion.

The chemical decomposition of a solid material by heat, producing flammable gases and vapors before combustion actually occurs. Pyrolysis explains how a solid fuel package becomes the gas-phase fuel that feeds the fire tetrahedron's chain reaction.

Flash point is the lowest temperature at which a liquid gives off enough vapor to ignite when an external ignition source (spark, flame) is applied. Autoignition temperature is the much higher temperature at which a fuel ignites spontaneously with no external ignition source needed.

Heat of combustion is the energy released per unit mass of a specific fuel when it burns. Fire load is the total quantity of combustible material, expressed per unit floor area, available to burn in a compartment. Fire load estimates potential severity; heat of combustion is a fuel-specific property.

Conduction (direct contact between materials), convection (movement of heated gases or liquids), and radiation (electromagnetic energy transfer requiring no contact medium). Investigators use these to explain fire spread paths and why fuels distant from the origin ignited.

Carbon monoxide (CO) from incomplete combustion is the leading cause of fire fatalities; hydrogen cyanide (HCN), released when nitrogen-containing synthetics like wool, nylon, and polyurethane burn, is also highly toxic; hydrogen chloride (HCl) forms when PVC burns and is corrosive to metal and lung tissue.

Ignition, growth, flashover, fully developed, and decay. A ventilation-limited fire in decay can also produce a backdraft if fresh air suddenly reaches accumulated unburned fuel gases. Investigators use these stages to interpret pattern severity and burn sequence.

The transition to full room involvement when radiant heat from the hot upper gas layer ignites most exposed combustibles nearly simultaneously, typically once the upper layer reaches roughly 600°C (about 1,100°F). After flashover, fire patterns become far less reliable for pinpointing origin because the whole compartment burns.

A rapid, sometimes explosive ignition of accumulated pyrolysis gases when oxygen is suddenly introduced to a ventilation-limited, oxygen-starved fire (e.g., opening a door). Unlike flashover, which is a heat-driven transition, a backdraft is triggered by a sudden change in ventilation/oxygen supply.

A ventilation-controlled fire's burning rate is limited by available oxygen, common in modern, tightly sealed compartments. A fuel-controlled fire's rate is limited by the amount and exposed surface area of fuel present, with ample oxygen available. Which regime applies affects how investigators read damage severity and pattern development.

HRR, measured in kW, is the key variable driving fire growth and flashover potential. As a fire grows, hot combustion gases rise and stratify into a hot upper layer over a cooler lower layer; ventilation openings and layer depth influence when — or if — flashover occurs.

Deflagration is subsonic flame-front propagation driven by heat transfer and describes most fuel-gas and dust explosions. Detonation is a supersonic shock-wave reaction typical of high explosives. The distinction affects expected damage patterns and the explosive source investigators should suspect.

The Lower Explosive Limit is the minimum vapor/gas concentration in air that will ignite; the Upper Explosive Limit is the maximum concentration that will still ignite — above it the mixture is too fuel-rich (too little oxygen). A BLEVE (boiling liquid expanding vapor explosion) occurs when a pressurized vessel containing a heated liquid ruptures catastrophically.

A V-shaped char or damage pattern on a vertical surface caused by the rising, expanding plume of hot gases and flame above a burning fuel package. Tracing the V down to its narrowest point helps locate — but does not by itself prove — the area of origin; multiple, unconnected V-patterns can indicate multiple origins.

Area of origin is the general location (room or zone) where the fire began, identified from pattern analysis and witness/fire-department information. Point of origin is the specific spot where the heat source and first fuel ignited actually met — a more precise finding that isn't always achievable.

A pattern where soot and combustion residue have been burned away from a surface, often exposed masonry or tile, due to intense, sustained direct flame or radiant heat contact. It indicates a location of high heat exposure and/or long duration — not automatically an accelerant.

Char depth measurements across a room can help triangulate origin, but NFPA 921 rejects the historic myth that large, shiny 'alligator' char blisters prove rapid heat release from an accelerant — any well-ventilated, intense fire can produce this pattern regardless of what fuel burned.

An irregular burn pattern on a floor may suggest a poured ignitable liquid, but NFPA 921 requires laboratory (GC-MS) confirmation of ignitable liquid residue before concluding one was present — melted synthetic floor coverings or dripping furniture can create a visually identical pattern.

Systematically documenting the location of electrical arc sites (short-circuit damage) on wiring throughout a structure and plotting them on a diagram. Because arcing generally stops once a conductor is de-energized or consumed, arc-mapped locations can help corroborate an area of origin identified through pattern analysis.

Accidental (no deliberate human act), natural (e.g., lightning), incendiary (deliberately set), and undetermined (insufficient evidence to support any single classification). NFPA 921 has no 'negligent' category — undetermined is a fully valid, often appropriate conclusion.

The rejected practice of concluding a fire was incendiary solely by eliminating all identified accidental and natural causes, without independent, affirmative evidence of an ignitable liquid or incendiary device. NFPA 921 explicitly disallows this reasoning — absence of an accidental cause is not proof of arson.

An ignition source with sufficient temperature, energy, and duration of contact with a fuel in the presence of oxygen to cause ignition. A valid cause hypothesis must identify a competent ignition source in contact with the first fuel ignited — not just plausible proximity.

The first material to sustain combustion after exposure to a competent heat source. Correctly identifying it — rather than whatever fuel later burned most or produced the deepest char — is essential to building a valid origin-and-cause hypothesis.

When two or more separate, independently ignited fire origins are documented in the same structure with no explainable accidental connection (fire spread, electrical fault path) between them, NFPA 921 treats this as a strong indicator of an incendiary cause.

The standard container for collecting fire debris suspected of containing ignitable liquid residue. They are vapor-tight, don't react with or absorb hydrocarbons, and prevent evaporation loss before lab analysis — unlike plastic bags, which can be permeable to some ignitable liquid vapors.

An unburned sample of the same material or substrate collected away from the suspected origin, used as a baseline to distinguish pyrolysis products naturally present in the material from an added ignitable liquid detected by lab analysis.

ASTM E1618 is the standard test method for identifying ignitable liquid residues in fire debris using gas chromatography-mass spectrometry (GC-MS). ASTM E1412 describes the passive headspace concentration technique (activated charcoal strip) used to extract those residues from debris before E1618 analysis.

Chain of custody is the documented, unbroken record of everyone who collected, handled, transported, and stored a piece of physical evidence. Spoliation is the loss, destruction, or alteration of evidence that compromises other parties' ability to examine it — a major concern in civil fire litigation.

A short circuit is unintended current flow between two conductors of a circuit; a ground fault is current flow from a conductor to ground, often through a grounded enclosure; overcurrent is current exceeding a conductor's or device's safe rating, generating excess heat. Each leaves different physical evidence on wiring.

A resolidified, often rounded bead of melted conductor material formed at the moment of an electrical arc. Finding an arc bead confirms an arc occurred there, but the investigator must still determine whether that arc caused the fire or was merely an effect of fire damage reaching still-energized wiring.

A loose, corroded, or otherwise poor electrical connection, such as a loose terminal screw, that creates localized resistance heating over time. This is a common accidental ignition source distinct from a sudden short circuit or overload event.

Recognize the need (a problem exists), define the problem, collect data, analyze the data, develop a hypothesis, test the hypothesis against all known data, and select a final hypothesis. Investigators must be willing to reject a hypothesis that new data disproves.

NFPA 921 requires inductive reasoning — forming a hypothesis from observed data, then testing it — rather than deductive reasoning, which assumes a conclusion first and selectively fits facts to support it. Inductive reasoning applied through the scientific method is the accepted methodology.

The tendency to notice, favor, and interpret evidence in a way that confirms a pre-existing conclusion, such as an early suspicion of arson, while discounting contradictory evidence. NFPA 921 identifies it as a significant threat to a valid fire cause determination.

A hypothesis must be tested against all the evidence in the case, not merely the evidence that supports it, and it must be capable of being disproven if it's actually wrong. Only a hypothesis that survives rigorous testing against all available data may be adopted as the final cause determination.

Standard practice moves from general, overall exterior and interior scene views to the area of origin, then to progressively closer photographs of specific evidence and patterns — preserving spatial context before isolating detail.

A ruler or labeled scale marker placed next to evidence in a photograph so the true size of the item or pattern can be determined later from the image alone, without relying on the photographer's estimate.

A scene-diagramming technique that measures an item of evidence's location from two fixed, permanent reference points, allowing its exact position to be recreated later on a scaled diagram — useful when a single measured baseline can't fix a point in two dimensions.

A systematic scene examination approach that removes fire debris in documented layers from the top down, rather than digging straight to the floor — preventing loss of information about fall patterns, collapse sequence, and the origin area's original contents.

U.S. Supreme Court decision holding that firefighters and investigators may remain in or re-enter a structure without a warrant for a reasonable time immediately following extinguishment to determine origin and cause, since exigent circumstances justified the original warrantless entry to fight the fire.

Follow-on Supreme Court decision holding that once investigators have left the scene, a new entry to search for evidence generally requires either consent or a warrant — administrative or criminal, depending on the investigation's purpose — since the original Tyler exigency doesn't extend indefinitely.

Daubert, used in federal courts and many states, requires a judge to assess an expert's methodology for reliability — testability, peer review, error rate, general acceptance — before allowing testimony. Frye, retained by some state courts, asks only whether the underlying scientific technique is generally accepted in the relevant field.

Preponderance of the evidence — more likely than not, roughly greater than 50% — is the burden of proof in civil fire litigation such as insurance subrogation. Beyond a reasonable doubt, a far higher burden, applies only in a criminal arson prosecution.

Investigators should interview witnesses, occupants, and first-arriving firefighters as soon as practical after the fire, while memories of fire conditions, smoke behavior, and events are freshest and least influenced by outside information or media coverage.

Open-ended questions, like 'What did you see when you arrived?', let a witness describe events in their own words without suggesting an answer. Leading questions, like 'Did you see a red glow?', risk contaminating the witness's recollection and are avoided in investigative interviews.

First-arriving firefighters can provide crucial data on smoke color/volume, flame location and color, and forcible-entry conditions such as locked or unlocked doors and windows — information that may not be recoverable from the physical scene after suppression and overhaul.

Conflicting statements between witnesses are treated as an investigative lead to reconcile or explore further — not, by themselves, proof of deception or an incendiary cause. NFPA 921 stresses corroborating witness information against physical scene evidence wherever possible.

Ionization detectors respond faster to the small combustion particles produced by flaming fires; photoelectric detectors respond faster to the larger smoke particles produced by smoldering fires. Knowing which type was installed helps explain detector-activation timing in a fire timeline.

A fire wall is a structural, fire-resistance-rated assembly, typically extending through the roof, that separates buildings or subdivides one into independently stable fire areas. A fire barrier is a non-structural, fire-resistance-rated assembly used to separate spaces within a single building, such as corridors or shafts.

Building codes classify construction by the fire-resistance rating and combustibility of structural elements: Type I is fire-resistive/non-combustible (highest rating), Type III is ordinary construction with masonry walls and a combustible interior, Type IV is heavy timber, and Type V is wood-frame construction (combustible throughout, lowest rating).