Ch14 Fire Suppression Flashcards
The science behind fire suppression…
To understand how to control fire, you need to know how fires are extinguished. This section describes methods used to interrupt the fire tetrahedron and extinguish a fire. p669
These methods are: Temperature reduction Fuel removal Oxygen exclusion Chemical flame inhibition
Cooling reduces the temperature of a fuel to a point where it does not produce sufficient vapours to burn… p670
The use of water for cooling is the most effective method available for extinguishment of smouldering fires.
Water absorbs significant heat as its temperature is raised, but it has its greatest effect when it is vaporized into steam. When water is converted to steam, it absorbs five times more energy than warming the liquid to the boiling point. p670
it also rapidly expands approximately 1700x. Because of this expansion rate, firefighters should avoid creating steam during interior attack.
Water can be used to control burning gases and reduce the temperature of hot products of combustion in the upper gas layer… p670
Cooling burning gases…
Limits or stops flaming combustion in the upper layer
Slows the pyrolysis process of combustible materials
Reduces the radiant heat flux from the upper layer
Reduces the potential for flashover
Excess steam production can reduce visibility, increase chances for steam burns, and disrupt the thermal layer… p670
Control steam production as follows…
Use good nozzle technique
Apply the appropriate amount of water
Apply water using the most effective form such as fog, straight, or solid stream based upon scene conditions.
Removing the fuel source effectively extinguishes any fire… p670
Removing the fuel is a more common tactic at... Ground cover fires Exterior stacked materials Vehicle fires Flammable liquid or gas fires
Oxygen exclusion… p671
Reducing the oxygen available to the combustion process reduces fire growth and may result in extinguishment over time.
Flooding a compartment with an inert gas such as carbon dioxide displaces the oxygen and disrupts the combustion process but, reduces the chance for occupant survivability. Blanketing some fuels with foam can displace oxygen. None of these methods work on fuels that are self oxidizing such as ammonium nitrate found in fertilizer.
Limiting the fire’s air supply can be a highly effective fire control action… p671
The simplest example of this is when a building occupant closes the door to the fire room before leaving the building. This limits the air supply to the fire and can prevent flashover.
Chemical flame inhibition… p672
Extinguishing agents such as some dry chemicals, halongentated agents (halons), and halon replacement clean agents, inhibit or interrupt the combustion reaction and stop flame production.
Making entry… p674
The following are pre entry considerations critical to firefighter safety and effectiveness…
Reading fire behaviour indicators
Understanding the crews tactical assignment
Identifying potential emergency escape routes
Evaluating forcible entry requirements
Identifying hazards
Verifying that radios are transmitting and receiving on the correct channel
Ensuring SCBA is ready to use
Doing a buddy check to ensure no skin is exposed
If the fire is vent controlled and the door is open, a significant increase in heat release rate can quickly occur. Unburned fuel in the form of smoke will escape at the top of the doorway, while fresh air will enter at the bottom, providing oxygen for fire development… p675
In this situation, cooling the hot gases overhead can reduce the risk of ignition and potential for flashover and provide a safer operating environment.
When the attack crew moves to the building entrance, they should stay low and out of the doorway while the door is forced open… p675
Use a TIC of small amount of water to see if the door is hot. If the door is hot the water will evaporate.
Flow paths… p676
Wind and open door ways create flow paths within a structure that increases fire growth and spread and can cause fire fighter causalities.
Because wind can cause unpredictable changes to the fire, you should attack with the wind at your back.
Gas cooling… p676
Gas cooling is a way of reducing heat release from the hot gas layer.
This technique is effective when faced with a shielded fire, which is a fire you cannot see from the doorway because it is located in a remote part of the structure or objects are shielding the fire.
Hot gases accumulating in the upper levels of a compartment can present problems for you and your crew.
Remember, smoke is fuel and may transition to rollover, flashover, or a smoke explosion. Cooling the hot gas layer slows the transfer of heat to other combustible and reduces the chances of overhead gases igniting.
Direct attack… p677
A direct attack on the fire using a solid or straight stream uses water most efficiently on free burning fires. The water is applied directly onto burning fuels until the fire is extinguished.
Indirect attack for a structure fire… p678
The indirect attack can be made from inside or outside a structure. The attack is made by directing the stream toward the ceiling to cool the room by banking the stream off the walls.
Combination attack… p679
A combination attack combines cooling the hot gas layer at the ceiling level using an indirect attack with a direct attack on the fuels burning on or near the floor. This method can look like painting a wall, making a T, and then making a circle with a solid stream.
Transitional attack… p679
Transitional attack uses an exterior fire attack through a ventilation opening to help a fire transition from vent limited conditions to fuel limited conditions. Transitional attack reduces the potential for flashover and creates a more survivable interior environment. Following this transitional attack, an interior attack crew can more easily make entry and reach the seat of the fire to complete fire suppression.
Fires in upper levels of structures… p680
In structures equipped with standpipe systems, the location of the standpipe connection determines the fire attack method. Standpipe connections in older structures may be located in corridors or near stairwells.
Fires in upper levels of structures, especially high rise buildings, can require large numbers of personnel to conduct large evacuations, carry tools and equipment to upper levels, and maintain a sustained fire attack. In many cases, firefighters must carry additional tools and equipment up many flights of stairs.
Residential basements… p682
Initial size up of any basement fire is essential because of extreme danger, especially with regards to structural collapse. Floor assemblies, especially when assemblies are unprotected, over basements can reach a point of collapse before firefighters arrive on scene.
Firefighters working on the floor above a basement fire and those fighting the fire are at an increased risk of floor collapse during operations and after extinguishment.
Residential basements… p683
Because of the inherent danger of using interior stairs for fire attack, any identified, alternative entrances to the basement should be communicated to a supervisor or IC as safer points of entry.
Interior and exterior enclosed stairwells can act as a flow path for smoke, flames, and heated gases, much like a fireplace chimney. Advancing attack hose lines down an enclosed stairwell may be the only avenue available, but it exposes firefighters to tremendous hazard.
Interior exposure protection… p684
Interior exposure protection generally involves closing doors or other openings between the fire area and the unaffected area and the proper use of tactical ventilation to ensure limited smoke movement.
Controlling ventilation with positive pressure in adjoined, uninvolved areas of a structure can also pressurize those areas and isolate the fire to one area of an overall structure.
