Paragraph 6 Protection against flammable conditionsF1

Hydrogen leakage and permeation from the compressed hydrogen storage system must not directly vent into the passenger compartment, or into any enclosed or semi-enclosed spaces within the hydrogen-fuelled vehicle that contain unprotected ignition sources.

Any single failure downstream of the main hydrogen shut-off valve must not result in accumulations in levels of hydrogen concentration in the passenger compartment.

The requirement in sub-paragraph (2) is met if the hydrogen concentration in the passenger compartment does not exceed 1.0% by volume when tested in accordance with sub-paragraph (4).

The test procedure for determining levels of hydrogen concentration in sub-paragraph (2) is the test procedure for integrity of enclosed spaces and detection systems in paragraph 3.2 of Annex 5 to ECE Regulation 134.02.

If, during operation, the hydrogen concentration exceeds 3.0% by volume in the air in the enclosed or semi-enclosed spaces of the hydrogen-fuelled vehicle, a warning must be provided in accordance with paragraph 7.

If, during operation, the hydrogen concentration exceeds 4.0% by volume in the air in the enclosed or semi-enclosed spaces of the hydrogen-fuelled vehicle, the main shut-off valve must be closed to isolate the compressed hydrogen storage system.