There are two ways to reduce polymer flammability. A few polymers (mostly thermosetting) can have their synthesis modified by replacing part of the starting materials chemically reactive halogenated analogues. In most cases, however, and especially with thermoplastics a different approach is necessary from an economic standpoint and this involves the incorporation of additives. This is often effective in delaying ignition, slowing the flame spread, reducing smoke or moderating the heat generation. Although it does not usualy stop burning altogether, especially in the case of serious fires.
The primary goal of adding flame retardants is to delay the ignition and burning of materials, allowing people more time to escape the affected area. A secondary consideration is to limit property damage.