The present study investigates the mechanical properties of newly developed FR chemical Fire-off in order to assess textile service-life features. 350 g/L Fire-off finished bath was prepared and CO/PET fabric samples were treated via impregnation method. In order to investigate FR performance of treated fabrics LOI test was performed. Subsequently, fabric strength, abrasion properties and outward appearance; tensile properties, abrasion, pilling performance and whiteness of Fire-off treated fabrics were tested and evaluated. Mechanical test results showed that there was a slight increase in strength, elongation, abrasion and pilling. On the other hand, whiteness and air permeability of fabrics were decreased after Fire-off treatment.