Regulation No. 118 of the United Nations Economic Commission for Europe (UN/ECE R118)1 lays down the technical specifications for evaluating the burning behavior and fuel repellency of materials used in bus interiors. Materials that pass the tests described in the relevant Annexes to the Regulation are granted type approval with regard to their burning behavior and/or their capability to repel fuels or lubricants.
Which materials require testing according to UN/ECE R118?
The Regulation applies to motor vehicles in Category M3, Classes II and III.2 This means buses with more than 8 seats in addition to the driver’s seat, weighing at least 5 tonnes, and intended primarily or exclusively for seated passengers. Any material or component used in such vehicles' interior, engine, or heating compartment should be tested according to UN/ECE R118 unless exempted under paragraph 6.2.8.
Evaluation of burning behavior
Tests to evaluate the burning behavior of bus interior components are described in Annexes 6 to 8 of UN/ECE R118. The compliance criteria and target materials for each test are summarized in Table 1. More information on the procedure and sample requirements can be found by clicking the test name.
Table 1: Overview of UN/ECE R118 reaction to fire tests
Test | Satisfactory results | Materials that require testing |
Burning rate ≤ 100 mm/min OR flame extinguished before last measuring point | Materials installed in a horizontal position, including insulation materials | |
No ignition of cotton wool placed under the sample (via flaming droplets) | Insulation materials, materials installed on the ceiling or > 500 mm above the seat cushion | |
Burning rate ≤ 100 mm/min OR flame extinguished before destroying one of the first marker threads | Materials installed in a vertical position, including insulation materials. Cable sleeves and conduits. |
If a material satisfies the requirements of the Annex 8 test, it is also considered compliant with the Annex 6 test. An alternative approach for meeting both Annex 7 and Annex 8 requirements is the ISO 5658-2 test, which measures lateral flame spread and critical heat flux at extinguishment (CFE). If this approach is chosen, the material must have an average CFE of ≥ 20 kW/m2 and must not produce flaming drops to comply with UN Regulation No. 118.
Evaluation of fuel and lubricant repellency
Insulation materials’ capacity to repel fuels and lubricants is assessed using a test described in Annex 9 to UN/ECE R118. In the test, four sample specimens measuring 140 mm x 140 mm x 5 mm are first conditioned under specified conditions and then exposed to diesel fuel for 24 hours. For satisfactory results, the weight of the worst-case sample specimen must not increase by 1 g or more.
Electrical cables’ resistance to flame propagation
Annex 10 to UN/ECE R118 describes a flame resistance test for electrical cables, required for any cable measuring more than 100 mm, used anywhere in the vehicle. To pass the test, the worst-case sample (out of five replicates) must be extinguished within 70 seconds and a minimum of 50 mm of insulation at the top of the sample must remain unburned.
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References:
1 The article is primarily based on the 2020 version of UN Regulation No 118 – Uniform technical prescriptions concerning the burning behaviour and/or the capability to repel fuel or lubricant of materials used in the construction of certain categories of motor vehicles [2020/241], available on EUR-Lex.
2 If the manufacturer requests it, the Regulation can also be applied to Category M3, Class I vehicles, which incorporate areas constructed for standing passengers. This change was introduced in June 2023 by Addendum 117 (Revision 3, Amendment 1) to UN Regulation No 118. More information on vehicle classification is found in the Consolidated Resolution on the Construction of Vehicles (R.E.3) by the United Nations Economic and Social Council.