Chapter 14 - Fire supression Flashcards
Ways to interrupt the fire tetrahedron
- Temperature reduction
- Fuel removal
- Oxygen exclusion
- Chemical flame inhibition
Temperature reduction
Extinguishment is cooling with water. Enough water must be applied to absorb the heat being generated and stop the gas phase chemical reaction.
- Reduces temp of a fuel to a point where is does not produce sufficient vapours to burn
- Can control burning gases and reduce temp of hot products of combustion in the upper gas layer
- Reduces heat flux from upper layer
- Reduces potential of flash over
Water
- Absorbs significant heat with its greatest effect when it is vaporized into steam. When converted to steam, it absorbs 5 times more energy than warming the liquid to the boiling point.
- It also rapidly expands approx. 1700 times. Avoid when doing interior FA due to reduced visibility, steam burns, and disruption of thermal layer
Fuel removal
- More common tactic at ground cover fires, exterior stacked material fires, vehicle fires and flammable liquid/gas fires (careful of run off)
- Stopping the flow of a liquid fuel
- Closing valves to stop the emission of gaseous fuels
- Moving solid fuels out of the path of the fire
Oxygen exclusion
Reducing available O2
- Method used for stove top fires, when a cover is placed on a pan of burning grease
- Flooding a compartment with CO2 displaces O2 but makes environment oxygen deficient
- Blanketing some fuels with foam can displace O2 (none will work on fuels that are self oxidizing such as ammonium nitrate found in fertilizer)
- Door control to limit O2 to fire
Chemical flame inhibition
- Dry chemicals, Halons, clean agents, inhibit or interrupt the combustion reaction and stop flame production.
- Effective on flaming fires.
- Impractical on smoldering fires because there is no effective means to cool the fuel and stop the chemical chain reaction.
Use a TIC or apply a small amount of water on the surface of the door in order to check for heat. If door is very hot, water will evaporate and convert to steam.
True
Fast air movement in at the bottom and smoke moving out at the top indicates an active fire in the structure
True
High volume of turbulent smoke and a low neutral plane (pre flashover conditions), apply water to the hot gas layer and do not enter
True
Gas cooling
Way of reducing heat release from the hot gas layer. Effective technique when faced with a shielded fire (a fire you cannot see from the door way because it is located in a remote part of the structure or objects are shielding the fire).
- Water droplets will fall out of the smoke layer in greater quantities as the layer cools
Direct attack
Using a solid or straight stream uses water most efficiently on free burning flames. Water is applied directly onto the burning fuels until fire is extinguished.
Indirect attack
Can be made from inside or outside structure. Directing the stream toward the ceiling to cool the room or by banking the stream off walls. Produces more steam and should be coordinated with ventilation.
- Do not upset the thermal layering; the steam produced will begin to condense, causing the smoke and heat to drop rapidly to the floor and move sluggishly thereafter
Combination attack
Combines cooling the hot gas layer using indirect attack with direct attack on the fuels burning near the floor level. Nozzle pattern U, N, Z, T or rotational manner.
Transitional attack
Uses an exterior fire attack through a ventilation opening to help a fire transition from vent limited to fuel limited. Reduces potential of flashover and makes a more survivable interior environment. Following this, an interior attack crew can more easily make entry and reach the seat of the fire.
Standpipe systems
- May be required in structures 3 stories or higher.
- Most located in stairwells, corridors, or protected stairways.
- If unprotected, connect on floor below. If found in protected, can connect on fire floor.
- Flake extra attack hoseline on first landing above fire floor so it will feed more easily into the fire floor
Below ground fires
Some of the most difficult and dangerous fires for FF
- If basement unfinished, exposed floor joists are exposed and will fail sooner than a ceiling protected with drywall.
- Supporting joists can collapse before the floor decking was burned through
- Interior and exterior enclosed stairwells can act as flow paths for smoke, flames, and heated gases
Basement fires are hot, and opening a vent point to allow O2 to enter is going to create more problems unless ventilation is coordinated with water applications
True
Exposure protection
Preventing a fire from spreading to unaffected areas. Unaffected areas are referred to as exposures and may exist inside or outside of a structure.
Interior exposure
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. Passive forms of exposure protection such as fire rated walls and doors are also used to prohibit fire and smoke movement.
Exterior exposures
Either remove the endangered persons, property, or items or apply a protective spray of water or foam extinguishing agent between the fire and the exposure.
Supporting fire protection systems
Should work with the system to control the fire. Most designed with control mode sprinklers. Only intended to control fire growth and prevent flashover. Complete suppression before turning off the system or unless given orders by IC.
FDC
Fire department connection
- Allow a pumper to supplement the water supply and pressure in a structures sprinkler or standpipe system.
Closing a main control valve
One means to stop the water flow from activated sprinkler heads (can also use wedges). Located between the sprinkler system and the main water supply. Control valve usually located directly under the sprinkler alarm valve, the dry pipe or deluge valve, or outside the building near the sprinkler system it controls.
Types of control valves
Outside screw and yoke (OS&Y) valve
Post indicator valve (PIV)
Wall post indicator valve (WPIV)
Post indicator valve assembly (PIVA)
Fire department personnel are not responsible for turning utilities back on and should not attempt to do so.
True
Only use the main power shutoff at the meter or the breaker box to shut down electricity to a structure.
True
Solar panels and photovoltaic panels
Most have 2 shutoff switches one on each side of the power inverter. Also a shutoff switch on the electric meter. Closing these will shut off power inside the structure, but it will not turn off the solar panel array as long as there is any amount of natural or artificial light, the panel is always on and generating power. Avoid these when performing tactical ventilation.
Natural gas
Pure form is Methane. Flammability range of 5% to 15% but is nontoxic. Lighter than air so it tends to rise. Classified as a asphyxiant because it may displace air in a confined space and lead to suffocation.
- No odour but utility companies add Mercaptan, which gives it a rotten egg smell.
- Meter usually located outside structure near the foundation. Can be inside in basement or mechanical space.
- When open, the tang (rectangular bar) is in line with the pipe.
Liquefied petroleum gas (LPG)
Also known as bottled gas. LPG refers to fuel gases stored in a liquid state under pressure. 2 main gases BUTANE and PROPANE(most used).
- propane has no natural odour, but added mercaptan gives it the distinct smell. Non toxic.
- LPG 1.5 times heavier than air.
- explosive range of 2-9.5%.
- lpg leak produces a visible cloud of vapour that hugs the ground
Vehicle fires
Variety of power sources; gasoline, diesel, electricity, hybrids, compressed or liquefied natural gas (CNG or LNG), biofuels, and hydrogen
