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23 Cards in this Set

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What do you call it when flammable gases in the top layer of a compartment ignite, creating a rolling flame front that travels across the top of the compartment?
Rollover/Flameover
What is flashover?
An event that occurs when all fuel packages in a compartment reach their ignition temperature and ignite. When this occurs, the fire has moved from the "growth" stage to full involvement. Flashover temperatures are extremely high, and force burning gases out of windows and doors at a high velocity.
What are the indicators for flashover?
1) Building (fire load, ventilation profile, thermal properties)

2) Smoke (hot gas layer lowering)

3) Air flow (strong bidirectional flow -- air in, smoke out)

4) Heat (rapidly increasing temperature)

5) Flame (ghosting, rollover)
What can a firefighter do to reduce ceiling temperature and try to prevent flashover?
1) Fire short sprays of water into the upper gas layer to cool it

2) Ventilation (only when ordered)
At what temperature does flashover occur?
Between 900º and 1200º F -- around the autoignition temperature of carbon monoxide
Most compartment fires that grow beyond the incipient stage become _____ _______.
Ventilation controlled
What two conditions must be present in order for flashover to occur?
1) Sufficient heat

2) Sufficient ventilation
Define "fully developed stage."
Stage of burning process where energy release is at maximum rate and is limited only by the availability of fuel and oxygen.
Define "decay stage."
Stage of fire development when fuel is consumed and energy release diminishes, and temperatures decrease. During this stage, the fire goes from ventilation controlled to fuel controlled.
Define "backdraft."
Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. The stalled combustion resumes with explosive force. It may occur because of inadequate or improper ventilation procedures.
What are some visual indicators of backdraft conditions?
1) Little to no visible flame

2) Inwardly drawn smoke

3) Smoke leaving building in puffs

4) Black smoke becoming dense gray-yellow

5) Pressurized smoke leaving through small openings.

6) Smoke stained windows

7) Heat-induced glass damage
If you begin ventilation procedures on a compartment that didn't initially look like it contained much of a fire and heavy smoke and flame suddenly issue from the vent, what might that indicate?
That might indicate that there is a lot of unburned fuel and high temperatures within the compartment waiting to explode in a backdraft.
Does backdraft occur immediately upon ventilating a compartment?
Usually no. It takes time for oxygen to mix with the hot gas layer.
What two characteristics of burning fuel have the most effect on fire development?
Mass and surface area
What are the six factors that affect fire development?
Fuel type

Availability and location of additional fuel

Compartment geometry

Ventilation

Thermal properties of the enclosure

Ambient conditions
What are a couple of interior finishing products that can quickly spread fire?
Simulated wood paneling, anything that incorporates polyurethane foam
What are the two main dangers posed by fire in a large compartment with high ceiling?
1) Compartment height can mask the actual effects of the fire, leaving conditions at floor level relatively unchanged

2) Large supply of oxygen
All things being equal, fire will develop more _____ in a large compartment.
slowly
Firefighters must account for preexisting ventilation as well as potential _____ in ventilation.
Changes
What are the four main methods of fire suppression?
Temperature reduction

Fuel removal

Oxygen exclusion

Chemical flame inhibition
What is a more effective cooling agent -- liquid water, or steam?
Steam. It has a greatly increased surface area so is more prone to absorbing heat. It also expands to be about 1700 times larger than water.
What is the preferred method of extinguishing pressurized gas fires, and fires where runoff would cause a significant health and safety threat?
Fuel removal (let it burn itself out)
What method of fire suppression is effective on gas and liquid fuels (because it suppresses flaming combustion), but isn't very effective on surface mode fires?
Chemical flame inhibition (using halon-replacement agents)