ISO 15500-12:2015 specifies tests and requirements for the pressure relief valve (PRV), a compressed natural gas fuel system component intended for use on the types of motor vehicles defined in ISO 3833.
ISO 15500-12:2015 is applicable to vehicles using natural gas in accordance with ISO 15403-1 (mono-fuel, bi-fuel, or dual-fuel applications). It is not applicable to the following:
a) liquefied natural gas (LNG) fuel system components located upstream of, and including, the vaporizer;
b) fuel containers;
c) stationary gas engines;
d) container mounting hardware;
e) electronic fuel management;
f) refuelling receptacles.
NOTE 1 It is recognized that miscellaneous components not specifically covered herein can be examined to meet the criteria of this part of ISO 15500 and tested according to the appropriate functional tests.
NOTE 2 All references to pressure in this part of ISO 15500 are to be considered gauge pressures unless otherwise specified.
NOTE 3 This part of ISO 15500 is based upon a service pressure for natural gas as a fuel of 20 MPa [200 bar] settled at 15 �C. Other service pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio). For example, a 25 MPa (250 bar) service pressure system will require pressures to be multiplied by 1,25.
 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2.