The terms Flame Resistant and Fire Retardant (both are commonly referred to as FR) get misused a lot. These two terms are very similar and can become confusing. The content below should make clear the differences of the two.
Flame and Fire can be used interchangeably. The confusion occurs when looking at Resistant vs. Retardant. These terms can be misleading and If you are required to use one, but buy the other you could get burned.
Resistant is defined as a material that is inherently resistant to catching fire (self-extinguishing) and does not melt or drip when exposed directly to extreme heat.
Retardant is defined as a material that has been chemically treated to self-extinguish. There are many textiles that can be “treated”. The melting and dripping of a fabric is the greatest safety concern because the melted material can cause great damage to skin.
It is important to keep in mind that the terminology and certification process differ greatly depending on the composition of the product, the chemical processes involved, the desired effects, and the actual effects.
Fire retardant coatings and fire resistant coatings usually do not provide the same functions therefore they should not be seen as interchangeable.
As seen here.