FIA Regulations - Standard 8856:2000
Standard 8856-2000 - PROTECTIVE CLOTHING FOR AUTOMOBILE DRIVERS
APPENDIX I - Item 3
Embroidery sewn directly onto the overall shall be stitched onto the outermost layer only, for better heat insulation.
Backing material of badges shall be flameproof and in conformity with the standard ISO 15025 in order to avoid combustion of the badge which would affect the efficiency of the overalls.
Thread used for affixing the badge to the overalls shall be flameproof and in conformity with the standard ISO 15025.
It is also recommended that embroidery thread on badges or on the outermost layer of the garment be flameproof and in conformity with the standard ISO 15025.
When affixing badges and signs to the overalls, heat-bonding shall not be used and the garment shall not be cut.
NB: any embroidery not complying with these conditions will result in the cancellation of the homologation of the overalls concerned, and its user may be excluded by the scrutineer of the event during which the infringement was noted.
Read full FIA Standard 8856:2000 here