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Examoogle • User • info@examoogle.com • EE-2024-8821
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Which method is used to generate form in foam type extinguisher method?
Chemical
Mechanical
Electrical
or B
or B
Quick Summary: Foam-type fire extinguishers generate foam to blanket flammable liquids and exclude oxygen from the fire. This can be achieved through a chemical reaction between two solutions or by mechanical aeration of a foam concentrate solution.
Foam-type fire extinguishers generate foam to blanket flammable liquids and exclude oxygen from the fire. This can be achieved through a chemical reaction between two solutions or by mechanical aeration of a foam concentrate solution.
2NaHCO3+Al2(SO4)3→Na2SO4+2Al(OH)3+6CO2
Foam Efficiency = Volume of SolutionVolume of Foam
In chemical foam extinguishers, an acid (like aluminum sulfate) and an alkali (like sodium bicarbonate) react to produce carbon dioxide gas and foam bubbles. In mechanical foam extinguishers, a foam-forming agent is mixed with water and air is forced into the mixture using a nozzle or aspirator to create stable bubbles.
Foam works primarily by the principle of 'smothering' (oxygen exclusion).
Chemical foam extinguishers are obsolete in many industrial standards but historically significant.
Mechanical foam (AFFF - Aqueous Film Forming Foam) is the modern industry standard.
Foam extinguishers should not be used on Class C (electrical) fires due to conductivity, unless specified otherwise.
Highly effective for Class B (flammable liquid) fires.
Creates a vapor seal to prevent re-ignition.
Chemical foam can be corrosive and leave messy residues.
Not suitable for energized electrical equipment.
Oil and fuel storage depots.
Aircraft hangars.
Industrial chemical processing areas.
| Feature | Chemical Foam | Mechanical Foam |
|---|---|---|
Generation Mechanism | Exothermic acid-base reaction | Mechanical air aspiration |
Mechanical foam is often referred to as AFFF.
Electrical fire suppression generally requires non-conductive agents like CO2 or Dry Chemical Powder (DCP).
D is correct — Foam for fire extinguishing is produced either by a chemical reaction between two reagents or by the mechanical aspiration of air into a foam-producing solution.
Always remember: Foam is for liquid fires; for Electrical fires (Class C/E), always prioritize CO2 or Halon/Clean Agents as they are non-conductive and leave no residue.