Fire Suppression Flashcards
What are the 4 methods firefighters use to interrupt the fire tetrahedron and extinguish a fire?
- Temperature reduction
- Fuel removal
- Oxygen exclusion
- Chemical flame inhibition
What is temperature reduction?
The controlling and extinguishment of fire by cooling with water, which reduces the temperature of a fuel to a point that it does not produce sufficient vapors to burn. To do this, enough water must be applied to absorb the heat being generated and stop the gas phase chemical reaction.
What is the most effective method for extinguishing smouldering fires?
Cooling with water (temperature reduction)
What lowers the risk that a ventilation-limited fire will reignite and re-enter the growth phase when it receives more oxygen?
A coordinated combination of cooling hot fire gases from the exterior using a straight stream and tactical ventilation.
When is cooling with water most effective?
Water absorbs significant heat as its temperature is raised, but it has its greatest effect when it is vaporized into steam as steam absorbs five times more energy than warming it to the boiling point.
What is a disadvantage of creating steam during interior fire attack?
It rapidly expands, approximately 1700 times, which can reduce visibility, increase the likelihood of steam burns, and disrupt the thermal layer. In order to control steam production, you should:
* Use good nozzle technique
* Apply the appropriate amount of water
* Apply water using the most effective form (i.e. fog, straight, or solid stream)
When is removing fuel a potential tatic for fire extinguishment?
Although removing fuel rarely extinguishes any fire, it is a common tactic at:
* Ground cover fires
* Exterior stacked material fires
* Vehicle fires
* Flammable liquid / gas fires
What 3 ways can fuel removal be performed?
- Allow a fire to burn until all available fuel is consumed
- Stop the flow of a liquid fuel
- Close valves to stop the emission of gaseous fuels
- Move solid fuels out of the path of the fire
How can oxygen exclusion be performed for fire control and extinguishment?
- Flooding a compartment with inert gas such as carbon dioxide to displace the oxygen
- Blanketing some fuels with foam (smothering)
- Controlling doors and windows into and within the structure
When is chemical flame inhibition used for fire control and extinguishment?
This method is effective on flaming fires. Agents such as dry chemicals, holagenated agents (halons), and halon-replacement “clean” agents, inhibit or interrupt the combustion reaction and stop flame production. Note that these agents do no easily extinguish nonflaming fires because there is no effective means to cool the fuel and stop the chemical chain reaction.
How does wind influence how fire is attacked?
Because wind can influence fire behavior, you should attack with the wind to your back.
What is gas cooling?
A way of reducing heat release from the hot gas layer. This is effective when faced with a shielded fire, which is a fire that you cannot see from the doorway because it is located in a remote part of the structure or there are objects shielding the fire. In these situations you cannot apply water directly to the fire without entering the room and working under the hot gas layer. Since this is dangerous, gas cooling slows down the transfer of heat to other combustibles and reduces the chances of the overhead gas igniting.
How should you cool the hot gas layer?
Direct short bursts or pulses of water into it.
What are the 3 methods of fire attack?
- Direct - water is applied directly onto burning fuels until the fire is extinguished
- Indirect - water is applied towards the ceiling or banked off the walls to cool the room. Note that this produces a more steam than a direct attack so it must be coordinated with ventilation. Once temperatures are reduced, firefighters can advance to make a direct attack on the fire. (Note that this can be done from inside or outside the structure.)
- Combination - combines cooling the hot gas layer at the ceiling level with a direct attack on the fuels burning near the floor level. To do this, move the nozzle from the area overhead to the floor in a Z, T, or rotational pattern.
What is a transitional fire attack?
A transitional attack uses an exterior fire attack with a straight stream through a ventilation opening to help a fire transition from ventilation-limited to fuel-limited. This reduces the potential for flashover and creates a more survivable interior environment for a subsequent interior attack. Note that if the transitional attack is done effectively, the interior crew can enter at the same time.
