British Standard 7175 Source 7 Polyester is inherently flame retardant & our sheets are woven using 76 ends of Trevira & 68 picks of Polyester (warp & weft). The advantage of Flame Retardant Polyester is that multiple washes do not effect the fabrics flame retardancy. Non-polyester fabrics which are proban treated leech through washing reducing the flame retardancy over time. This loomstate fabric is dyed to shade & cut & sewn into the bed linen. The fabric has been tested by an independent test house & has been accredited with British Standard 7175-Crib 7 Source 7. The ignitability of the bedcovers & pillows by smouldering ignition sources have also been tested on this product. Finishing agents now used in production of polyester are such that the feel of the linen is similar to a polycotton blend. Therefore, the historical negative perception of polyester being a harsh fabric has been overcome through these enhanced dyeing & finishing processes.