What is the ordinary base (standard) dry chemical in B.C. type extinguishers?

• A. Ammonium sulfate
• B. Bicarbonate of sodium
• C. Potassium chloride
• D. Sodium bicarbonate

Answer: (B)

The correct answer is bicarbonate of sodium, as it is commonly used as the ordinary base in type BC dry chemical fire extinguishers. This substance is effective in extinguishing fires that involve flammable liquids and gases, making it a suitable choice for use in a variety of settings, including industrial and commercial environments.

Bicarbonate of sodium works by releasing carbon dioxide when it reacts under heat, effectively suppressing flames and preventing the re-ignition of the fire. It is favored for its ability to coat the fuel with a layer that prevents oxygen from supporting the combustion process.

Other substances listed, while they may have properties suited for different applications, do not hold the same effectiveness or common usage in BC extinguishers. Ammonium sulfate and potassium chloride are used in other types of fire extinguishers but are not standard in BC types. Sodium bicarbonate, while it has similar applications to bicarbonate of sodium, is not the agent primarily identified with BC extinguishers. Therefore, bicarbonate of sodium is recognized as the ordinary base chemical for this purpose.