BS ISO 15501-1-2025 PDF

Full title and description

STB BS ISO 15501-1-2025 — Road vehicles — Compressed natural gas (CNG) fuel systems — Part 1: Safety requirements. This document specifies the minimum safety requirements for on‑board compressed natural gas fuel systems used in road vehicles (mono‑fuel, bi‑fuel and dual‑fuel), covering original production and converted vehicles and defining functional, design and safety expectations for system assemblies and components.

Abstract

This standard sets out minimum safety requirements applicable to the functionality of on‑board CNG fuel systems for the types of motor vehicles defined in ISO 3833. It applies to vehicles using CNG in accordance with ISO 15403‑1 and covers system design, installation interfaces, protection and safety provisions needed to minimise risk of leakage, ignition and overpressure during normal operation, maintenance and foreseeable misuse. Matters relating to the skills of installers and converters are excluded.

General information

• Status: Published
• Publication date: 01 December 2025
• Publisher: International Organization for Standardization (ISO). Also published/adopted in national form as BS ISO 15501-1:2025 by the British Standards Institution (BSI); may be available under local designations such as STB in some jurisdictions.
• ICS / categories: 43.060.40 (Fuel systems for road vehicles)
• Edition / version: Edition 4 (2025)
• Number of pages: 15 (ISO edition; pagination can vary for national/adopted publications)

Scope

The standard applies to CNG on‑board fuel systems intended for the types of motor vehicles defined in ISO 3833 and to vehicles using compressed natural gas in accordance with ISO 15403‑1. It defines minimum safety requirements for system functionality, including design and protective measures to prevent and mitigate leaks, overpressure and other hazards. The scope includes mono‑fuel, bi‑fuel and dual‑fuel arrangements and both original production and converted vehicles. Installer and converter competency requirements are explicitly outside the scope.

Key topics and requirements

• System applicability: mono‑fuel, bi‑fuel and dual‑fuel vehicle systems and conversions.
• Functional safety requirements for CNG on‑board systems (design, installation interfaces and operational safety).
• Pressure containment, overpressure protection and relief provisions for storage and secondary circuits.
• Leak prevention, detection and mitigation measures; routing and protection of fuel lines and components.
• Component and assembly marking, identification and traceability requirements.
• Requirements for gas quality compatibility (reference to ISO 15403‑1) and material selection.
• References to mandatory test methods (see Part 2) and to component test standards (ISO 15500 series, ISO 11439, ISO 14469 where applicable).
• Requirements for documentation, instructions for safe use and maintenance information intended for manufacturers and converters.

Typical use and users

Used by vehicle manufacturers (OEMs), conversion companies, CNG system and component manufacturers, design and safety engineers, test laboratories, certification bodies and regulatory authorities. It is also a reference for procurement, type‑approval and conformity assessment of CNG fuel systems and for technical authors preparing installation and maintenance documentation.

Related standards

Key related documents include ISO 15501‑2 (Test methods for Part 1 requirements), the ISO 15500 series (individual component standards for CNG systems), ISO 3833 (vehicle categories), ISO 15403‑1 (natural gas for vehicles — fuel specifications) and test/component standards such as ISO 11439 and ISO 14469. National adoptions (e.g., BS ISO 15501‑1:2025, STB versions) reproduce the ISO requirements with possible national forewords or pagination differences.

Keywords

CNG, compressed natural gas, fuel systems, road vehicles, safety requirements, ISO 15501, BS ISO, STB, fuel system testing, leak prevention, overpressure protection, vehicle conversions, ISO 15403, ISO 15500.

FAQ

Q: What is this standard?

A: ISO 15501‑1:2025 (published also as national adoptions such as BS ISO 15501‑1:2025) specifies minimum safety requirements for on‑board compressed natural gas (CNG) fuel systems for road vehicles.

Q: What does it cover?

A: It covers functional and safety requirements for CNG on‑board systems (design, containment, protection, marking and documentation) for mono‑, bi‑ and dual‑fuel vehicles, including original production and converted vehicles. Installer competence requirements are excluded.

Q: Who typically uses it?

A: OEMs, CNG system and component manufacturers, vehicle converters, test houses, certification and approval bodies, regulators, and engineering teams responsible for CNG vehicle design and safety.

Q: Is it current or superseded?

A: The 2025 edition is the current published edition (Edition 4, 2025). It replaces earlier editions (for example the 2016 edition and its amendments).

Q: Is it part of a series?

A: Yes. Part 1 (safety requirements) is complemented by Part 2 (test methods). The ISO 15501 series sits alongside the ISO 15500 component series and references other norms such as ISO 15403‑1 and ISO 3833.

Q: What are the key keywords?

A: CNG, compressed natural gas, fuel systems, safety requirements, road vehicles, ISO 15501, test methods, fuel system components, conversions.