Chapter 7 Portable Fire Extinguishers (Block 1/Test 1)
Saponification
A phenomenon that occurs when mixtures of alkaline-based chemicals and certain cooking oils come into contact resulting in the formation of a soapy foam.
Aqueous Film Forming Foam (AFFF)
Are intended for class B fires, useful in combating fires or suppressing vapors from small liquid fuel spills
Classification of Portable Fire Extinguishers
Classified by the type of fire they are designed to effectively extinguish. There are 5 classes of portable fire extinguishers to the match the 5 classes of fire. Class A, B, C, D, and K
Clean Agent Extinguishers
Designed specifically yo replace Halon, which would remove the oxygen from an environment, causing hazards for fire fighters. Are discharged as a rapidly evaporating liquid that leaves no residue. The agents effectively cool and smother fires in class A and B fuels and the agents are non conductive so they can be used on class C fires.
Class C Ratings
Essentially class A or class B fires involving energized electrical equipment. This rating confirms that the extinguishing agent will not conduct electricity
Class K
Involve combustable cooking oils such as vegetable or animal fats and oils that burn at high temp. Mostly found in Kitchens but may be found in private homes. Wet chemical systems are used to extinguish these fires.
Class D
Involve combustable metals and alloys such as lithium, magnesium, potassium, and sodium. Dry powDer extinguishers work best on these types of fires. Do not confuse dry chem with dry powder.
Class C
Involve energized electrical equipment, water cannot be used because until the electrical energy has been eliminated. Class C extinguishers will not conduct electricity making them suitable for electrical fires. C = Computer
Class B
Involve flammable and combustable liquids and gases such as alcohol, gasoline, oils, and petroleum gas
Carbon Dioxide (CO2) Extinguisher
Most effective in extinguishing class B and C fires. Discharged in the form of a gas, has limited reach and can be dispersed in wind
Class K Ratings
Must be capable of saponifying (Converting the fatty acids or fats to a soap or foam)
Identifying Portable Fire Extinguishers
One system uses geometric shapes of specific color with the class letter shown within the shape. The second system uses pictographs to make the selection of the most appropriate extinguisher.
Class A
Ordinary combustibles such as textiles, paper, plastics, rubber, and wood. Can be easily extinguished with water or dry chemical
Using Portable Fire Extinguishers
P - Pull the pin A - Aim at the base of the fire S - Squeeze the handles together S - Sweep the nozzle back and forth to cover the burning material
Class A Ratings
Rated from 1-A through 40-A. Ratings are based on the amount of extinguishing agent and the duration and range of the discharge.
Class B Ratings
Rated from 1-B and 640-B. Rating is based on the approximate square foot area of a flammable liquid fire that a nonexpert operator can extinguish using one full extinguisher.
Types of Fire Extinguishers
Smothering - excluding O2 from the burning process Cooling - Reducing the burning material below its ignition temp Chain breaking - interrupting the chemical chain reaction in the burning process Saponification - Forming an O2 excluding soapy foam surface
Dry Chemical Extinguisher
Used on Class A, B and C fires. Among the most common fire extinguisher. Two types: Regular B or C rated and multipurpose A, B and C rated.
Dry Powder Extinguisher
Used to control and extinguish class D fires involving combustable metals
Inspecting and Maintaining Portable Fire Extinguishers
Will be done once a month to ensure that they are accessible and operable. Hydro static testing will be done every 6 or 12 years depending on the extinguisher
Class D Ratings
Will vary depending on the type of metal being burned. These factors are considered during testing: Reaction between the metal and the agent, toxicity of the agent, toxicity of the fumes produced, time to allow metal to burn completely without fire suppression compared to the time to extinguish the fire using an extinguisher.