Let me say I do have numerous Ex installations on my site, but due to reasons I have to move them to a new facility.

Shall I apply to new regulations, or I may use all installation as it is?

I would say this is the most frequent asked questions which we daily face...

In the new facility it shall be considered as a new installation. This installation shall comply with latest regulations. At least the manufacturer shall confirm compliance to it in an updated DoC - at least! Most of cases it is not enough - this specially goes for non electrical Ex installations. Here again you may face situation becoming manufacturer.

Keep up good work!