I know Nema 7 enclosure can be used for hazardous location, can we
1. used a pressurized Nema 4x location for hazardous environment?
2. if yes, can it be certified from a third party?
i learned somewhere, Pressurized Nema 4x enclosure can be used for hazardous environment but cannot be certified.
Not my are area but I did a quick glance at NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment and there doesn't appear to be a requirement for any specific NEMA type enclosure.
Certified is something that needs definition, generally different depending on where you are in the world. North America has a set of standards, Europe has another. There are commonalities, but before wasting any more time on it you need to start with which standards and certifications you need.
But as a general statement, there are indeed companies that specialize in this and offer "certified" systems, both in North America and in other parts of the world.