# The Road Vehicles (Construction and Use) Regulations 1986, Paragraph 5: Discharge from other pressure relief devices


(1) The hydrogen gas discharge from other pressure relief devices that are not thermally-activated, including burst discs, must not be directed—
(a) towards exposed electrical terminals, exposed electrical switches or other ignition sources;
(b) into or towards the passenger compartment;
(c) into or towards any vehicle wheel housing;
(d) towards each container.
(2) At the hydrogen-fuelled vehicle exhaust system’s point of discharge, the hydrogen concentration level must not exceed—
(a) 4.0% average by volume during any moving three-second time interval during normal operation, including start-up and shut-down;
(b) 8.0% at any time.
(3) The test procedure that must be followed, for determining the hydrogen concentration level in sub-paragraph (2), is the compliance test for the vehicle exhaust system in paragraph 4 of Annex 5 to ECE Regulation 134.02.

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Source: https://www.legislation.gov.uk/uksi/1986/1078/schedule/5A/paragraph/5 (the official version)
Page: https://openlegislation.uk/road-vehicles-construction-and-use-regulations-1986/schedule-5A/paragraph-5
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.