In 1959, the U.S. Navy Research Laboratory developed a dry chemical called _____, which is five times more effective that CO2.

In 1959, the U.S. Navy Research Laboratory developed a dry chemical called _____, which is five times more effective that CO2.

• A. Monoammonium phosphate
• B. ABC powder
• C. Purple K
• D. Dry chemical X

Answer: (C)

Fires are often controlled best when you interrupt the flame’s chemical reactions as well as cool and separate the fuel. Purple K is a dry chemical extinguishing agent based on potassium bicarbonate, developed by the U.S. Navy Research Laboratory in 1959. Its strength comes from two effects: it chemically interferes with the flame’s radical chain reactions (the H, O, and OH species that propagate combustion) and it blankets the fuel surface, helping to prevent vapor release and reignition. That combination makes it far more effective than CO2 for many fires, commonly described as about five times more effective, especially for hydrocarbon and electrical fires. CO2 mainly displaces oxygen and cools, but it doesn’t disrupt flame chemistry to the same degree, so its performance can be limited in enclosed spaces or on certain fuels. Other powders like monoammonium phosphate (ABC) are versatile but don’t offer the same rapid chemical suppression advantage as Purple K, while a fictional “Dry chemical X” isn’t used in practice.

Fires are often controlled best when you interrupt the flame’s chemical reactions as well as cool and separate the fuel. Purple K is a dry chemical extinguishing agent based on potassium bicarbonate, developed by the U.S. Navy Research Laboratory in 1959. Its strength comes from two effects: it chemically interferes with the flame’s radical chain reactions (the H, O, and OH species that propagate combustion) and it blankets the fuel surface, helping to prevent vapor release and reignition. That combination makes it far more effective than CO2 for many fires, commonly described as about five times more effective, especially for hydrocarbon and electrical fires. CO2 mainly displaces oxygen and cools, but it doesn’t disrupt flame chemistry to the same degree, so its performance can be limited in enclosed spaces or on certain fuels. Other powders like monoammonium phosphate (ABC) are versatile but don’t offer the same rapid chemical suppression advantage as Purple K, while a fictional “Dry chemical X” isn’t used in practice.