UN R51 specifies that conditioning of a silencing system is necessary only in cases where exhaust gases come into contact with silencer fibrous materials. This proposal would apply the same concept in L category noise regulations.

11. The expert from IMMA presented revised collective amendments to Regulations Nos. 9, 41, 63 and 92 to clarify that the provisions on fibrous materials are only applicable if such materials are in contact with exhaust gases (GRB-63-02). GRB adopted the proposals (Annexes III – VI) and requested the secretariat to submit them to WP.29 and AC.1 for consideration and vote at their June 2016 sessions as a draft Supplement 2 to the 07 series of amendments to Regulation No. 9, a draft Supplement 5 to the 04 series of amendments to Regulation No. 41, a draft Supplement 2 to the 02 series of amendments to Regulation No. 63 and a draft Supplement 1 to the 01 series of amendments to Regulation No. 92.