What is the primary purpose of intumescent seals in fire-rated assemblies?

• A. To expand when heated to maintain the integrity of the seal.
• B. To improve sound insulation.
• C. To enhance decorative appearance.
• D. To prevent movement.

Answer: (A)

The main idea is that these seals respond to heat by swelling and expanding to fill gaps in fire-rated assemblies. When exposed to high temperatures, the intumescent material undergoes a controlled chemical reaction and enlarges several times its original thickness, blocking the opening around doors, penetrations, or joints. This expansion creates an insulating barrier that slows or stops the spread of flames, smoke, and hot gases, helping the assembly maintain its fire-resistance rating during a fire. They aren’t primarily used for sound insulation, decoration, or preventing movement, so their essential function is to expand when heated to preserve the seal and the integrity of the fire-rated assembly.