Chemistry and Physics of Fire - Chapter 4

Fill-in-the-blank flashcards covering the chemistry and physics of fire from the lecture notes.

Fire is a rapid, self-sustaining __ process.

oxidation

Combustion is a chemical reaction that releases energy as heat and usually as __.

light

The Fire Triangle consists of __, oxidizer, and energy.

fuel

The Fire Tetrahedron adds a fourth component: __.

chemical chain reaction

Oxidizers are substances that evolve or generate __.

oxygen

Air is approximately 21 percent __.

oxygen

Calcium hypochlorite releases __ when heated.

oxygen

An oxidizer used in blasting agents is __ nitrate.

ammonium

The by-products of complete combustion are and .

water vapor and carbon dioxide

A term recently officially recognized is __ fire.

black

A fuel is anything that will __.

burn

Carbon and hydrogen are the two most common elements in __.

fuels

Fuels may exist in solid, liquid, and __ states.

gas

Combustion usually occurs when the fuel has been converted to the __ state.

gaseous

Pyrolysis is the chemical decomposition of matter through the action of __.

heat

Some fuels do not have to convert to the vapor state to burn, such as __.

pure carbon

Ignition temperature is reached when the fuel becomes self-sustaining and continues combustion without any external input of __.

heat

As heat is added, long molecules break down into shorter molecules, forming short-chain hydrocarbons and free __.

radicals

Sufficient amounts of oxidizer and an ignition source of sufficient __ must be present.

temperature

Solid fuels: factors affecting pyrolization include mass, arrangement, continuity, and __ content.

moisture

Mass affects ignition; smaller fuels like dust or chips require less heat to __.

pyrolize

Continuity is the grouping of fuel over an area; an example of vertical arrangement is dry grass spreading fire upward into brush and trees, illustrating vertical __.

continuity

Moisture content affects ignition; on humid days, fuels may absorb moisture making ignition __.

difficult

The surface-burning characteristics rating indicates the relative rate of flame spread and is not a measure of the material's __.

fire resistance

The Steiner Tunnel (ASTM E-84) test measures flame spread, smoke density, and __.

temperature

Liquids: mixability is the ability to mix with water; most flammable liquids are __ (nonmixable) with water.

nonmixable

Specific gravity: most flammable liquids have SG less than 1.0 and will __ on water.

float

Vapor pressure is temperature __ dependent.

dependent

The boiling point occurs when vapor pressure equals the atmospheric pressure at the surface; liquids boil and the vapor leaves as __.

vapor

Vapor density is the relative density of a vapor or gas as compared to __.

air

Flash point is the minimum temperature at which vapors form an ignitable mixture; flammable liquids have flash points below __.

100°F

Gases can be categorized as flammable and nonflammable; oxygen itself does not burn, but fires burn more rapidly if the oxygen concentration is __.

increased

Upper flammable limit is the maximum concentration of gas in air above which it is not possible to __.

ignite the vapors

Lower flammable limit is the minimum concentration in air below which ignition is not possible to __.

ignite

The flammable range is the proportion of gas in air between the upper and lower flammable limits; this proportion is expressed as a __.

percent

When a compressed gas is released, the visible vapor cloud is a __ caused by condensation.

fog

Ignition temperature vs flash point: the __ is the minimum temperature for ignitable vapors.

flash point

Vapor density: vapors with density greater than air will __.

sink

Backdraft is a dangerous condition when oxygen is introduced to hot, fuel-rich gases; it is also known as a __.

smoke explosion

Incipient stage: oxygen in surrounding air is about __ percent.

21

Growth stage: the fire __ in intensity.

increases

Free Burning stage: heat brings more fuel to its __ temperature.

ignition

In a confined space, ceiling temperatures can reach about __ °F.

1000