1. swelling up or becoming enlarged, especially due to heat or moisture
Usage: technical; often used in materials science and fire safety

Examples

• The intumescent coating on the steel beam expanded when exposed to high temperatures.
• Intumescent paint provides fire protection by swelling to form an insulating layer.
• The wood treatment included intumescent chemicals that would activate during a fire.
• Engineers specified intumescent materials for the building’s fire safety system.
• The intumescent sealant expanded to block smoke and flames from spreading.
• Fire doors often contain intumescent strips that swell when heated.