Chapter 6 - Fire Extinguishers Flashcards
Class A (Ordinary combustibles)
Green triangle. Includes fuels such as wood, paper, plastic, rubber and cloth. Includes ratings 1A through 40A (1A=5L).
- Extinguished with water and water-based agents like class A foam.
- Dry chemicals also extinguish fires fuelled by class A materials.
Class B (Flammable and combustible liquids and gases)
Red box. Includes all hydrocarbons and alcohol based liquids and gases that will support combustion. Examples include: alcohol, gasoline, lubricating oils and liquefied petroleum gas (LPG). Rated 1B through 640B (based on approx. sq ft).
- Agents used include CO2, dry chemicals and class B foam.
Class C (Electrical)
Blue circle. Includes all fires involving energized electrical equipment. No ratings.
- Water and water-based foam conduct electrical current and should not be used until electricity has been shut off.
- Once power supply is shut off, FF can treat the fire as either class A or B.
Class D (Combustible metals)
Yellow star. Examples of combustible metals: magnesium, potassium, titanium, sodium, lithium and zirconium. No ratings.
- Mag fires can be identified by bright white emissions during combustion process. Located in cameras, laptops, luggage, box springs, automobile wheels and transmissions
- Water will cause class D fires to react violently, emit bits of molten metal.
- Dry powder works best (not the same as dry chemical).
Class K (Kitchen/cooking oils)
Black hexagon. Includes unsaturated cooking oils in well-insulated cooking appliances located in commercial kitchens. No ratings.
- vegetable or animal fats, vegetable oil, canola oil, peanut oil
- Wet chemical agents, suppress fire and smother it
- Extinguishers on class K work due to Saponification (converts the fatty acids or fats in the oils to a soapy film).
Extinguishing agents use at least 1 of the following to extinguish fires
Smothering - excluding O2 from the burning process
Cooling - reducing the burning material below its ignition temp
Chemical flame inhibition - Interrupting the chemical chain reaction in the burning process
Saponification - Forming an O2-excluding soapy foam surface
Mechanisms that fire extinguishers use to expel their contents
Manual pump
Stored pressure (also called air-pressurized water, APW)
Pressure cartridge
AFFF
Aqueous film forming foam
- Intended for class B fires
- Useful in suppressing vapours from small liquid fuel spills
- Has air-aspirating foam nozzle that aerates the foam solution, producing better quality foam than standard nozzles
- Finished foam floats on the surface of the fuel that are lighter than water
- Creates a vapour seal that extinguishes the flame and prevents reignition
- Do not apply the foam directly onto the fuel, rather, allow it to rain down gently onto the fuels surface or deflect the foam off a nearby surface or object
Water-mist extinguishers
Stored pressure that uses deionized water as the agent and nozzles that produce a fine spray instead of a solid stream. Impurities in water make it conduct electricity, the deionized water makes these class A extinguishers safe to use on class C fires.
Clean agent extinguishers
Effectively cool and smother fires in class A and B fuels and inhibit the sustained chemical reaction in class C fuels.
- These agents are nonconductive and can work on energized electrical equipment fires
- Been developed to replace Halons, also known as halogenated extinguishing agents (halons have a damaging effect on the atmospheres ozone layer)
- Halotron is an alternative clean agent that does not impact the ozone layer
CO2 extinguishers
Most effective in class B and C fires. Available as handheld and wheeled units.
- Stored under its own pressure as a liquified gas
- Usually forms dry icy crystals or carbon dioxide “snow” (very little cooling effect on the fire)
- When the extinguishers discharge CO2, a static electrical charge builds up on the discharge horn. Touching the horn before the charge has dissipated can result in a shock.
- Wheeled units, 50-100 lbs, common in airports and industrial facilities. Must deploy and unwind the hose.
Dry chemical extinguishers
Used on class A, B, C fires and/or class B/C fires. Dry POWDER only for class D.
- Most common today.
- 2 basic types: regular B/C rated and multipurpose and A/B/C rated
Handheld units
Cartridge operated or stored pressure (200 psi/1400 kPa)
Dry powder extinguishers
Class D metal/alloy fires. Can be deployed with portable extinguishers or applied either either a shovel or a scoop.
- Apply gently to avoid breaking any crust that may form over the burning metal
Inspecting an extinguisher immediately before use
External condition, hose/nozzle, weight and pressure gauge
