Can We Use Purge Panel in Flameproof Area?

There is no such thing as a "flameproof area".

EEx p, explosion protection by purge pressurisation, is permitted in hazardous areas Zone 1 and Zone 2 in Europe, however, note that if an operator is placed in Zone 1, then the organisation risks prosecution on Health and Safety grounds.

http://en.wikipedia.org/wiki/Electrical_equipment_in_hazardous_areas

Please stop work on the project until suitable hazardous area electrical equipment training has been completed.

The inside of the ultra high vacuum chambers we use are completely flameproof once they have been purged of air. At these pressures things do not ignite, they either melt or sublimate.

I still find it disturbing that anonymous posters come to an international public forum about a safety question. I hope that the lack of relevant information from the AP is due to English not being a native tongue.

The absence of appropriate training is more troubling, which is highlit by the original question being posted and the use of incorrect terminology in that post. The expression "flameproof area" is singularly inappropriate, for were an incendive spark to appear in that area at the same time as a potentially explosive atmosphere, the term "flameproof" would be completely contrary to what would happen. One might equally use the term "increased safety area", "purge-pressurise area", powder-filled area", "encapsulated area" or "oil-filled area"; these terms attempt to link the method of protection to the area classification, which is wrong as there are several explosion protection techniques applicable to each zone.

<...ultra high vacuum chambers...>

One wouldn't zone the inside of a gasoline/petrol engine cylinder either, for although there is a hazardous gas-air mixture more-or-less continuously present together with an electrical source of ignition, that is the intent of the equipment.

Sure. Just be sure to use flameproof matches to light your smokes.

It depends on what the zone is and the standard it is certified to. Do you know this information?

If you plan to put an ATEX or IECEx certified Ex p panel in an ATEX or IECEx certified Zone 0, then no you cannot. Zone 1 is VERY expensive, Zone 2 is easier. I don't have much experience on US standard DIV certified panels, but it will likely be similar.

Talk with a local supplier directly that deals with hazardous area applications as an Ex p system is a custom-designed and certified system and not something you can just buy and then stick stuff into.