What type of insulation is used on boilers?

• A. Fiberglass
• B. Mineral wool
• C. Cellulose
• D. Polystyrene

Answer: (B)

Boilers operate at very high temperatures, so the insulation around them must stay noncombustible and endure heat without breaking down. Mineral wool fits that need because it’s inorganic and heat-tolerant, so it won’t burn or melt when exposed to boiler temperatures. It provides strong thermal resistance, helping keep heat inside the boiler and reduce the risk to surrounding components, while also remaining stable and durable over time.

Fiberglass is also heat-stable, but mineral wool generally offers superior fire resistance and can withstand higher temperatures. The other options—cellulose and polystyrene—are flammable or degrade under heat, making them unsuitable for boiler insulation.