Epoxy is used for everything from garage floor coatings to structural repairs to electronics potting. It comes in two parts — a resin and a hardener — that react to form a rigid thermoset plastic. Its fire behavior changes significantly depending on whether it’s in liquid form or fully cured.

Liquid epoxy resin is flammable; cured epoxy is much less so. Uncured epoxy resin typically has a flash point between 300–400°F (149–204°C), which makes it a combustible liquid. The hardener component varies — some amine hardeners are more volatile and have lower flash points. Once cured, epoxy forms a cross-linked thermoset polymer that is significantly harder to ignite, though it will still burn in a sustained fire.

Safety During Application

When working with liquid epoxy:

• Keep away from open flames, sparks, and heat sources
• Ventilate the work area — epoxy vapors can accumulate
• The exothermic reaction during curing generates heat; large mixed batches can reach temperatures high enough to smoke or cause fires if left in a bucket — pour thin layers rather than leaving a deep pool of mixed epoxy
• Hardener components can be corrosive; read the SDS for your specific product

Cured Epoxy in Fires

Fully cured epoxy is classified as a combustible solid. It won’t ignite from a spark or incidental heat, but it will burn in a sustained fire and contributes fuel load. Epoxy coatings on garage floors and epoxy-bonded boat hulls contribute to fire spread and smoke production when a building or vessel is burning. The smoke from burning cured epoxy contains irritating and potentially toxic compounds.

High-Temperature Epoxy

Specialty high-temperature epoxies formulated for use near exhaust systems or industrial equipment are more fire-resistant, but even these aren’t fireproof. They’re rated to maintain structural integrity up to certain temperatures (often 250–300°F / 121–149°C) rather than to resist combustion. For a related comparison, see our article on whether resin is flammable.