Provbitarna, som måste vara uttöjda 20 %, skall bli utsatta för luft vid 40 °C med en ozonkoncentration av 0,5 ppm under 120 timmar. ###>The test-pieces, which have to be stretched to an elongation of 20 per cent shall have to be exposed to air of 40 °C with an ozone-concentration of 50 parts per hundred million during 120 hours.