Proposal to amend para. A.1.3.2.1. to modify the PEMS consistency check of exhaust mass flow and gas concentrations for fuels with a molar carbon to hydrogen ratio of 0. For such fuels, the formula in para. 8.4.1.6. of Annex 4 shall be used instead, with Equations 30 and 31 applied for Type 1A dual-fuel hydrogen engines. The verification shall not apply to engines operated on non-carbon fuels or dual-fuel engines when operated in dual-fuel mode with at least one fuel having a molar carbon to hydrogen ratio of 0.