Fire Prevention Flashcards

Questions and Answers

What are the four components to the Fire Tetrahedron?

Fuel, Oxygen (or oxidizers), Heat, Chemical Reaction

What are oxidizers?

Substances that can release oxygen during combustion

Provide examples of oxidizers.

H2O2, Cl2, H2SO4

The richer the oxygen, the higher the ignition temperature.

False Signup and view all the answers

Define Class A Fire.

Carbon based products, wood, paper Signup and view all the answers

Define Class B Fire.

Flammable gases and liquids Signup and view all the answers

Define Class C Fire.

Combustible materials where electricity may be present Signup and view all the answers

Define Class D Fire.

Combustible metals, aluminum, magnesium, titanium, sodium Signup and view all the answers

Define Class K Fire.

Liquid cooking media Signup and view all the answers

What is pyrolysis?

The chemical decomposition of a solid substance through heat action Signup and view all the answers

The ease of ignition is affected by _____

surface-to-mass ratio Signup and view all the answers

What are the two fuel-related factors involved in combustion?

The physical state of the fuel and its distribution Signup and view all the answers

Liquids burn, not vapours.

False Signup and view all the answers

Fuel in a gaseous state must be mixed with a(n) _____ in the proper ratio for combustion to occur.

oxidizer (air) Signup and view all the answers

What is the lower flammable limit (LFL)?

The minimum concentration of gas in air that can ignite Signup and view all the answers

What is an explosive range?

The range of vapour mixture that will ignite when subjected to an ignition source Signup and view all the answers

Explain spontaneous heating.

Heat accumulates to the point where spontaneous ignition occurs. Signup and view all the answers

Combustion cannot occur when concentrations are above or below the _ or _.

UFL, LFL Signup and view all the answers

What is flashover?

The sudden transition from local to widespread burning of all exposed fuels Signup and view all the answers

What causes backdraft?

When oxygen is introduced into a compartment, causing the fire to grow rapidly Signup and view all the answers

What is the main difference between a fire and an explosion?

The rate of energy release Signup and view all the answers

What is exothermic?

Releases heat Signup and view all the answers

How does heat flow?

Heat flows from a hot substance to a cold substance Signup and view all the answers

Study Notes

Fire Tetrahedron Components

Four essential elements: Fuel, Oxygen (or oxidizers), Heat, and Chemical Reaction.

Oxidizers

Substances, such as H2O2, Cl2, and H2SO4, that release oxygen during combustion, facilitating fire.

Classifications of Fires

Class A Fire: Involves combustible materials like wood and paper.
Class B Fire: Pertains to flammable gases and liquids.
Class C Fire: Involves fires where electricity is present.
Class D Fire: Combustible metals like aluminum and magnesium are involved.
Class K Fire: Relates to fires involving cooking oils and fats.

Combustion Dynamics

Ease of ignition increases with a higher surface-to-mass ratio and larger surface area, lowering ignition temperatures.
Fuels exist in multiple states: solid, liquid, or gas, but must typically be in gaseous form or vapor to combust.

Gas Characteristics

Combustion occurs when a gaseous fuel is mixed with an oxidizer in the appropriate ratio.
Flammable range is defined as the percentage of gas in the air necessary for combustion.
LFL (Lower Flammable Limit) and UFL (Upper Flammable Limit) indicate concentrations at which combustion cannot occur.

Vapor Behavior

Vapour density compares the density of gases with air; lighter gases (density less than 1) rise, while heavier gases sink.
Specific gravity measures the density of liquids in relation to water, influencing whether a substance sinks or floats.

Heat and Energy

Heat affects combustion; the conservation of mass and energy principles define that these cannot be created or destroyed, only transformed.
Chemical reactions during combustion produce heat and light alongside byproducts like smoke and fire gases, which can be lethal.

Fire Behavior in Spaces

Thermal Layering: Gases stratify by temperature, with the hottest gases at the ceiling.
Mushrooming: Heat and smoke rise until they encounter obstructions and spread laterally before descending.

Fire Dynamics

Ignition temperature is the threshold at which a substance ignites, while flashpoint is the minimum temperature for vaporization sufficient for burning.
Different stages of a fire: beginning phase, free burning (growth phase), and smoldering (decay phase).

Explosions and Combustion Types

Flashover: Rapid transition from localized fire to widespread burning.
Backdraft: Explosive growth when oxygen enters a confined space post-smoldering phase.
Distinction between deflagration (slow combustion wave) and detonation (shockwave faster than sound).

Chemical Reactions

Combustion is an exothermic reaction, releasing heat. Both heat and friction can serve as ignition sources.
Spontaneous Heating: Occurs when heat accumulates without escaping, often seen with certain organic materials.

Unique Mixtures

Hypergolic Mixtures: Fuels and oxidizers that ignite on contact without external ignition sources.
Anergols: Fuels and oxidizers that do not react when combined.

Effects of Fire Products

Heat leads to increased heart rates, dehydration, and burns; smoke causes reduced visibility and respiratory issues.
Primary cause of fatalities in fires is typically smoke and fire gases.

Energy and Heat Transfer

Heat flows from warmer to cooler substances; the transfer rate is influenced by temperature differences.
Molecular action within substances generates heat, allowing for combustion and contributing to fire dynamics.

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Description

Test your knowledge on fire prevention concepts with these flashcards. Explore key components like the Fire Tetrahedron and the role of oxidizers in combustion. Perfect for anyone studying fire safety or preparing for related certifications.