Which type of extinguishing agent is suitable for all classes of fires except Class D?

The suitable extinguishing agent for all classes of fires except Class D is dry chemicals. Dry chemical agents, such as ABC powder, are effective in extinguishing fires involving solids (Class A), flammable liquids (Class B), and gases (Class C) by interrupting the chemical reaction of the fire. These agents work by creating a barrier between the fuel and the oxygen or by interrupting the combustion process.

Class D fires, which involve combustible metals such as magnesium, titanium, or sodium, require specialized extinguishing agents because dry chemicals can react adversely with these metals, potentially exacerbating the fire. Hence, while dry chemicals are versatile and effective across a wide range of fire classes, their use is not appropriate for situations involving combustible metals.

In contrast, other agents like foam and water are effective against Class A and Class B fires but not suitable for electrical fires (Class C) or combustible metals (Class D). Carbon dioxide is effective for Class B and C fires but does not work on Class A fires. Therefore, dry chemicals are distinct in their wide applicability while being limited when it comes to Class D fires.