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
PASS
Pull
Aim
Squeeze
Sweep
- Approach upwind (wind at your back)
Once extinguisher is empty…
Lay on its side. Signals to others that they are empty.
Water type extinguishers
Protected against freezing if exposed to temps less than 4C. Use of adding antifreeze or storing in warm areas.
Considerations Related to Suppressing Incipient Fires
- Apply agent so it reaches but does not disturb the fuel surface
- After fire diminishes, you may move closer for final extinguishment
- Shut off electricity before attempting to extinguish Class C fires
Wet chemical extinguisher
Class K. Potassium-based, low-pH agent that extinguishes by saponification.
Dry Chemical Extinguishers- Additives and Agents
- Make agents moisture-resistant and prevent them from caking
- Keeps agents ready to use after long storage time
- Can be mildly corrosive and or produce a cloud of airborne particulate
- Some compatible with foam
