Division 5.4.1 General

Sound absorbing fibrous materials may only be used in silencing systems, or components thereof, where any of the following conditions are fulfilled:

1. (a)

   the exhaust gas is not in contact with the fibrous materials;

2. (b)

   the silencing system, or the components thereof, are of the same design family as systems, or components thereof, for which it has been proven, in the course of the type-approval process in accordance with the requirements of this Regulation, that they are not subject to deterioration.

Unless one of those conditions is fulfilled, the complete silencing system, or components thereof, shall be submitted to conventional conditioning using one of the three installations and procedures described below.

For the purposes of point (b) of the first subparagraph, a group of silencing system or silencing system components thereof shall be considered as being of the same design family when all of the following characteristics are the same:

1. (a)

   the presence of net gas flow of the exhaust gases through the absorbing fibrous material when in contact with that material;

2. (b)

   the type of the fibres;

3. (c)

   where applicable, binder material specifications;

4. (d)

   average fibre dimensions;

5. (e)

   minimum bulk material packing density in kg/m³;

6. (f)

   maximum contact surface between the gas flow and the absorbing material;