The best suggestion I could give is to seek info from an NRTL (UL, etc). I assume you are refering to tap devices similar to Kuppl-Tap, that allow a tap without removal of insulation from the conductors.
As to the suggested "expert" and link posted above, if you follow the link it takes you to a page of what appears to be primarily an HVAC contractor that also does electrical. Looking thru the webpage, I see no HVAC, or Electrical License numbers, which are required by State regs, but may be an oversite by this company.
As the OP in this thread is in Tunisia, he may look into an NRTL that is approved for that country, or an NRTL in Europe/Asia.