TEST

Q1 what is the molar mass value of hydrogen? [read the answer]

Q2 after 30 june 2003 all products for hazardous areas placed on the market or put into service will have to conform to a European Cummunity Directive. Which one? [read the answer]

Q3 how is classified the area close a ball valve outdoor installed in a pipe in which flows methan at 3 bar pressure and at 30 °C? [read the answer]