Flameproof is the word normally used by Asian & other commonwealth countries. Explosion proof is an American Word. EExd is used by all EU. There is no difference except term.
Flameproof design is one of the explosion protection technique extensively used for light fittings, JBs, motors in hazardous areas. This is certified by IEC but is predominantly followed in India and is also governed by local IS standards.
However, hazardous area specification you have asked for the transmitter is quite common and you should get it (ex-proof) from most of the reputed manufacturers.