Fire Prevention & Hazard Analysis Flashcards

Which analysis technique quantifies the probability of an undesired top event by combining the probabilities of basic failure events using AND/OR logic gates?

Answer: Fault Tree Analysis (FTA)

Fault Tree Analysis is a deductive, top-down method that uses Boolean AND/OR logic gates to model combinations of failures leading to the undesired top event.

The Limiting Oxygen Concentration (LOC) for a flammable gas mixture is the oxygen concentration below which:

Answer: Flame propagation cannot occur regardless of fuel concentration

The LOC (also called the Minimum Oxygen Concentration, MOC) is the threshold below which there is insufficient oxygen to support flame propagation, regardless of how much fuel is present.

NFPA 921, Guide for Fire and Explosion Investigations, classifies a fire's origin determination as which level of certainty when it is supported by physical evidence and eliminates all other hypotheses?

Answer: Conclusive

NFPA 921 uses the scientific method, and a 'conclusive' determination means the hypothesis is supported by physical evidence and all other reasonable hypotheses have been eliminated.

For an ordinary Class A fuel, the critical heat flux below which ignition cannot occur is approximately:

Answer: 10–20 kW/m²

Typical Class A solid fuels require an incident heat flux of approximately 10–20 kW/m² to reach piloted ignition; below this threshold, sustained ignition does not occur.

When a hazardous materials spill creates a flammable vapor cloud, the zone where the vapor-air mixture is above the UFL is considered:

Answer: Too rich to ignite

Above the Upper Flammable Limit (UFL), the mixture is too fuel-rich (lacks sufficient oxygen) to ignite; however, dilution by air can bring it into the flammable range.

Which document provides guidance on conducting a Damage-Limiting Construction (DLC) assessment for facilities handling explosive or highly flammable materials?

Answer: NFPA 68 (Explosion Protection by Deflagration Venting)

NFPA 68 covers explosion protection through deflagration venting, which is a primary DLC strategy that limits structural and equipment damage from internal deflagrations.

In a fire risk assessment, 'residual risk' is defined as the risk that remains after:

Answer: All reasonably practicable control measures have been implemented

Residual risk is the remaining level of risk after all reasonably practicable prevention and mitigation controls have been put in place; it must be evaluated against acceptance criteria.