Which extinguishing agent works by blanketing the fire to prevent oxygen in the air from contacting the fire or vapour?

Which extinguishing agent works by blanketing the fire to prevent oxygen in the air from contacting the fire or vapour?

• A. Foam
• B. Water
• C. Carbon dioxide
• D. Dry chemical powder

Answer: (A)

Foam extinguishing agent works by forming a stable layer on top of the flammable liquid, creating a blanket that keeps air from contacting the fuel or its vapours. That surface film both separates the fuel from the oxygen in the air and helps trap vapours, while the bubbles contribute cooling. This combination effectively starves the flame of the oxidizer and reduces vapour ignition risk. Water mainly cools the fuel and can spread the burn, rather than creating a surface blanket. Carbon dioxide displaces the surrounding air to reduce oxygen, but it doesn’t form the protective foam-covered layer over the liquid. Dry chemical powder interrupts chemical reactions or coats surfaces to limit flame propagation, not by forming a surface blanket over the fuel.

Foam extinguishing agent works by forming a stable layer on top of the flammable liquid, creating a blanket that keeps air from contacting the fuel or its vapours. That surface film both separates the fuel from the oxygen in the air and helps trap vapours, while the bubbles contribute cooling. This combination effectively starves the flame of the oxidizer and reduces vapour ignition risk.

Water mainly cools the fuel and can spread the burn, rather than creating a surface blanket. Carbon dioxide displaces the surrounding air to reduce oxygen, but it doesn’t form the protective foam-covered layer over the liquid. Dry chemical powder interrupts chemical reactions or coats surfaces to limit flame propagation, not by forming a surface blanket over the fuel.