FE Extinguishing Agent Properties & Chemistry 2

Question 1

Which extinguishing agent is specifically recommended for Class K fires involving cooking oils and fats in commercial kitchens?

Accepted Answer

Wet chemical potassium acetate solution

Answer

Wet chemical agents (potassium acetate, potassium carbonate, or potassium citrate) are designed for Class K fires because they react with hot cooking oils to form a soapy foam layer via saponification.

Question 2

AFFF (Aqueous Film-Forming Foam) creates a suppression layer on flammable liquid fires by which mechanism?

Accepted Answer

Forming a thin aqueous film that seals the fuel surface

Answer

AFFF works by spreading a thin aqueous film over the fuel surface that seals vapors, preventing them from reaching the flame, while also cooling the fuel with water.

Question 3

What minimum temperature limitation is a critical operational concern for CO2 extinguishers during discharge?

Accepted Answer

The discharge creates temperatures as low as -110°F (-79°C) at the horn

Answer

CO2 expands rapidly during discharge, dropping to approximately -110°F (-79°C) at the horn, which can cause frostbite if the horn is held improperly during use.

Question 4

Monoammonium phosphate (MAP), the active ingredient in ABC extinguishers, melts on contact with burning Class A materials. Why is this significant?

Accepted Answer

It forms a vitreous coating that seals the fuel surface and prevents re-ignition

Answer

When MAP contacts hot Class A surfaces, it melts and forms a glassy (vitreous) coating that seals oxygen away from the fuel, which is why ABC extinguishers are effective on ordinary combustibles.

Question 5

Which clean agent is most widely used as a replacement for Halon 1301 in fixed suppression systems?

Accepted Answer

FM-200 (HFC-227ea)

Answer

FM-200 (HFC-227ea) is the most widely used halon alternative for total-flooding applications because it has zero ozone depletion potential and extinguishes fires at low concentrations.

(FE) Certified Portable Fire Extinguisher Technician Practice Test

(FE) Certified Portable Fire Extinguisher Technician Practice Test

FE Extinguishing Agent Properties & Chemistry 2