There are a number of ways in which the self-sustaining combustion cycle can be interrupted. Whatever the method used, the end goal is to reduce the rate of heat transfer to the polymer and thus remove the fuel supply.
In total there are four processes involved with flammability: preheating, decomposition, ignition and combustion/propagation. If you are looking for more information about fire retardant sprays you may lead here https://cyndan.com.au/specialty-coatings/fire-retardant-liquid-timber-flame-retardant-chemical-prote.
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Preheating involves heating of this material by way of an external source, which increases the temperature of the substance at a rate that's dependent upon the thermal durability of the ignition source, the thermal conductivity of the substance, the specific heat of the substance, and the latent heat of fusion and vaporization of the material.
When sufficiently heated, the material starts to degrade, i.e. it loses its initial properties as the weakest bonds start to break down.
Gaseous combustion products are formed, the rate being dependent upon such factors like the intensity of outside heat, the temperature necessary for decomposition, and speed of decomposition.
The concentration of flammable gases then increases until it reaches a level which permits continuing oxidation in the presence of the ignition source. The ignition characteristics of the gas and the availability of oxygen are two major factors in any ignition process, and those attributes are prevalent in this situation.
After ignition and removal of the ignition source, combustion gets self-propagating if sufficient heat is generated and is radiated back to the substance to continue the decomposition procedure.