Get ready, this one is a mouthful: IECEx stands for the International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres.
In a nutshell, this is the international body that oversees the requirements for Explosion Hazardous Areas as defined by IEC standards. These standards cover both equipment and the manufacturing processes used to create it. The standards are also used for certifying Ex professionals.
The IECEx commission focuses on the framework for how IEC standards for Explosion Hazardous areas are interpreted and applied in practice. Markets such as Australia may not have their own dedicated authority, in which case they look to the IECEx for direction. However, local authorities in all markets make the actual laws and requirements, such as how ATEX defines commercial rules for Ex products in the EU. IECEx is in that sense not a legal body that can dictate rules.
INMETRO Short for Brazilian Institute of Metrology, Standardization and Industrial Quality. This is Brazil’s approval agency looking after Ex products. INMETRO follows IEC standards but have additional rules for the Brazilian market much like ATEX in the EU.