The building codes focus on preventing the spread of fire within and between buildings. A fire barrier is a wall assembly that has been tested and certified to withstand and contain a fire for a particular time duration.
A fire partition is a fire barrier that prevents the spread of fire between the sections of a building. A firewall is a structural fire barrier between buildings that is designed to remain standing during and after a fire.
Flame spread is a tested value of how fast a material burns compared to red oak planks.
A thermal barrier is a sheeting material that protects the materials behind it from reaching a temperature of 250°F or breeching during a fire. One-half-inch drywall is the most commonly used thermal barrier and is rated for 15 minutes of protection. Fire partitions in multifamily buildings usually require a wall assembly with a 2-hour rating.
An ignition barrier is a material used with foam insulation to prevent the foam from igniting. The code specifies a number of materials that can serve as ignition barriers including drywall, plywood, fibrous insulation, galvanized steel, and intumescent paint.