CFI (FAA) cheat sheet

Fire tetrahedron: fuel, oxidizer, heat, and chemical chain reaction; flaming combustion requires all four, while smoldering requires only fuel, oxygen, and heat.

Flash point = lowest temperature at which a liquid produces sufficient vapor to ignite momentarily; fire point = temperature at which vapor sustains burning (typically a few degrees higher).

Flammable limits: below the lower flammable limit (LFL) the mixture is too lean; above the upper flammable limit (UFL) it is too rich; both are temperature- and pressure-dependent.

Heat release rate (HRR) is energy per unit time (kW); peak HRR and compartment ventilation control flashover timing and fire growth.

Flashover indicators: upper-layer gas temperature about 600 C (1,100 F), floor heat flux about 20 kW/m2, and rollover of flames in the overhead.

Radiant heat flux follows q'' = epsilon-sigma-T^4; doubling absolute temperature increases radiant emission 16-fold.

Pyrolysis is thermal decomposition of solids into combustible gases; smoldering is flameless surface oxidation sustained by char.

Backdraft requires a ventilation-limited, fuel-rich fire and sudden oxygen introduction; the resulting deflagration propagates through accumulated hot gases.

Fire classes: A ordinary combustibles, B flammable liquids, C energized electrical, D combustible metals, K cooking oils.

Construction types I-V: I fire-resistive, II noncombustible, III ordinary masonry, IV heavy timber, V wood frame; Type V is most common in residential dwellings.

Fire resistance rating is hours an assembly withstands a standard fire test (ASTM E119/UL 263) without failure of integrity, insulation, or structural load capacity.

Lightweight wood trusses and engineered I-joists fail faster than solid-dimension lumber and create early collapse hazards in fire.

Wet-pipe sprinklers hold water under pressure and discharge on bulb failure; dry-pipe systems use air pressure and admit water after the valve trips.

Standard sprinkler glass bulb activation ratings: 68 C (155 F) is common in light-hazard occupancies.

Standpipe classes: I = 2.5-inch outlets for fire department; II = 1.5-inch for occupant use; III = both.

Fire alarm system functions: initiation (detection), notification (alarms), and control (HVAC shutdown, door release, suppression).

Utility identification includes electric service and meter, natural gas meter and shutoff, and water supply main; gas odorant is mercaptan.

Needed fire flow (NFF) estimates water demand; insufficient supply is a common cause of defensive firefighting and total loss.

Origin is the location where a fire began; cause is the sequence of circumstances that brought ignition source and fuel together.

NFPA 921 scientific method: identify problem, collect data, develop hypothesis, test hypothesis, select final hypothesis.

Fire patterns include V-pattern, hourglass, pour, char, oxidation, and heat lines; patterns must be interpreted with ventilation and fuel load.

Alligatoring (char crazing) is not a reliable indicator of fire intensity or origin and should not be used alone.

Cause classifications: accidental, natural, incendiary, undetermined; each requires documented evidence and reasoning.

Negative corpus - declaring incendiary because accidental causes were not found - is prohibited by NFPA 921.

Area of origin is broader than point of origin; point is the specific location of the first material ignited.

Arc mapping and arc bead analysis may support origin only when wiring was energized and fire-caused damage is established.

Fault tree analysis maps initiating events to failure paths and is used to test competing cause hypotheses.

Document the scene before disturbing it: photographs, video, sketches, and notes establish baseline conditions.

Photographic sequence: overall, mid-range, and close-up views, with scale and identification in each close-up.

Chain of custody records every transfer of evidence, from collection to laboratory to court; gaps can make evidence inadmissible.

Fire debris is collected in clean metal cans or approved vapor-tight bags; headspace analysis detects ignitable liquid residues.

Control samples from unaffected areas distinguish background materials from ignitable liquids and are required for defensible lab results.

Grid, strip, zone, and spiral search patterns ensure systematic coverage; grid is common for fire scenes.

Biological evidence is packaged in paper (breathable) containers; ignitable-liquid evidence in metal cans to prevent vapor loss.

Scene security log records all persons entering and leaving, preserving integrity and supporting later testimony.

Deflagration propagates at subsonic speed; detonation propagates supersonic with a shock wave; both produce overpressure and thermal effects.

BLEVE: pressurized liquid above its boiling point in a failed vessel rapidly vaporizes, producing fireball, blast, and projectile hazards.

Dust explosion pentagon: combustible dust, oxygen, ignition source, dispersion, and confinement; all five are required.

Vapor cloud explosion requires a flammable gas or liquid release, mixing within flammable limits, confinement or congestion, and an ignition source.

Overpressure effects: about 1 psi breaks glass; about 5 psi damages buildings; 15-20 psi risks lung injury; about 35 psi is often lethal.

TNT equivalence relates blast energy to mass of TNT and is used for estimating explosive charge size from damage.

Post-blast indicators: cratering, fragment directionality, seat of explosion, and deformation patterns help locate the charge.

Flammable limits: natural gas (methane) about 5-15 percent in air; propane about 2.1-9.5 percent in air.

Arc mapping plots arc sites on a circuit; it can locate a fault only if the circuit was energized and arcing was caused by the fire, not by suppression or collapse.

Copper melts at approximately 1,083 C (1,982 F); arc beads and melted conductors require metallurgical analysis to distinguish cause.

Overcurrent protection (fuses, breakers) protects wiring from overload and short circuits but does not prevent all glowing connections.

Glowing connections are high-resistance joints that heat without arcing and can ignite nearby combustibles; loose terminals are common causes.

AFCI protects against arc faults; GFCI protects against ground-fault shock; neither is a substitute for proper circuit design.

Vehicle fire causes include fuel system leaks, electrical faults, catalytic converter heat, and collision; EV battery thermal runaway can re-ignite.

High-voltage EV systems use orange cables and require de-energization and PPE before examination; 12 V systems remain hazardous.

Aluminum branch-circuit wiring is prone to loose connections and overheating; copper pigtails and CO/ALR devices are common remedies.

Cognitive interview: reinstate context, use open-ended prompts, vary retrieval order, and avoid suggestion to improve recall.

Ask open-ended questions first, then funnel to specific, non-leading questions; avoid questions that suggest the desired answer.

Eyewitness memory is affected by estimator variables (lighting, distance) and system variables (interviewer technique).

Miranda warnings are required only for custodial interrogation; voluntary non-custodial interviews do not require them.

Interview is non-accusatory fact gathering; interrogation is accusatory and designed to elicit admissions.

Reports should document who, what, when, where, how, and why, plus evidence handling and reasoning.

Corroborate witness statements with physical evidence; do not treat witness certainty as a reliable measure of accuracy.

Record interviews by audio/video or verbatim notes; document date, time, location, and persons present.

NFPA 921 is a guide for fire and explosion investigations; NFPA 1033 is the standard for professional qualifications of fire investigators.

NFPA 921 scientific method steps: recognize need, define problem, collect data, develop hypothesis, test hypothesis, select final hypothesis.

Hypotheses must be testable and falsifiable; conclusions must be supported by data, not by elimination alone.

NFPA 1033 requires knowledge in 16 topics, including fire chemistry, thermodynamics, building construction, and legal issues.

NFPA 1033 requires investigators to keep current with professional literature and continuing education.

Daubert factors: testability, peer review, error rate, and general acceptance; Frye requires general acceptance only.

Relevant codes include NFPA 1/IFC, NFPA 70 (NEC), NFPA 101 (Life Safety Code), and NFPA 13 (sprinklers).

Burden of proof in civil cases is preponderance of the evidence; in criminal cases it is beyond a reasonable doubt.

Expert testimony admissibility: Daubert (federal gatekeeping factors) or Frye (general acceptance), depending on jurisdiction.

Qualification is established through education, training, experience, and licensure; opposing counsel may challenge via voir dire.

Chain of custody gaps and contaminated evidence can lead to exclusion or reduced weight at trial.

Spoliation is loss or destruction of evidence; it can result in sanctions, adverse inference, or separate liability.

Subrogation allows an insurer that paid a loss to pursue recovery from the responsible party.

Work product and attorney-client privilege may protect investigation materials; document facts separately from opinions.

Expert reports should state opinions with basis and reasoning, avoid conclusory language, and disclose all data considered.

Depositions and discovery require accurate records; inconsistent prior statements can impeach testimony.

PPE and SCBA are required in smoke and post-fire atmospheres; two-in/two-out applies to interior structural firefighting.

Air monitoring for LEL, CO, HCN, and oxygen deficiency precedes entry into burned structures.

Scene hazards include structural instability, electrical shock, hazmat, sharp debris, and carbon monoxide.

Ethics require avoiding conflicts of interest, maintaining confidentiality, and disclosing limitations of findings.

Case management includes evidence tracking, budget control, expert coordination, and documentation of decisions.

Laboratory accreditation to ISO/IEC 17025 supports reliability of forensic analyses.

Cognitive bias (confirmation, anchoring) should be mitigated by peer review and consideration of alternative hypotheses.

Data security protects case files and evidence records; retain materials per legal holds and retention policies.