Drywall is a popular material for lining walls, building interior walls and providing firebreaks in modern buildings. It has a high flame resistance, save for the paper covering on the individual drywall sheets, and is therefore difficult to burn. Without a very high temperature available, the core of a drywall sheet is effectively inflammable, which makes it an excellent material for building firebreak barriers in the home and workplace.
The composition of drywall makes it difficult to burn. Drywall is a mixture of gypsum and water, pressed between sheets of paper. While the paper itself is flammable and burning will evaporate the water, it takes a very high temperature to burn gypsum. As a result, it is not possible to fully burn drywall outside of industrial furnaces.
The gypsum in drywall is difficult to burn but it will dry as the water content evaporates when burning and then begin the flake. The particles that are then given off can, when inhaled, cause health problems. As a result, it is not recommended to burn drywall for safety reasons.
Drywall is highly fire resistant due to the presence of water in the gypsum, which evaporates and thereby actively lowers the temperature of the surrounding material. While the paper covering will burn readily, the gypsum core of the drywall will remain mostly intact. The fire resistance of drywall makes it a popular choice for firebreaks in modern buildings.
Gypsum is a form of mineral, similar to clay and other plasters. As a result, it has a very high melting point and is difficult to set alight outside of industrial furnaces and other similar heat sources. The high gypsum content of drywall therefore provides substantial fire resistance and means that, for most purposes, drywall cannot be fully burned.