What is ISO 22241‑4 - Refilling interface for the NOx reduction agent AUS 32 about?
ISO 22241 is a series of international standards on diesel engines that discusses the NOx reduction agent AUS 32.
ISO 22241‑4 is the fourth part of the ISO 22241 series of documents that specifies the refilling interface for the NOx reduction agent AUS 32 which is needed to operate converters with a selective catalytic reduction (SCR) exhaust treatment system.
ISO 22241‑4 specifies the minimum functional and geometric requirements of an open refilling system, in order to ensure compatibility between the onboard refilling system and the offboard refilling system.
Compatibility conditions for a sealed refilling system are provided in ISO 22241‑4.
NOTE: ISO 22241‑4 applies to commercial vehicles and buses and has a gross vehicle mass of more than 3,5 t, designed to use stationary off-board refilling systems.
NOTE: ISO 22241‑4 also applies to the nozzle of stationary off-board refilling systems.
Who is ISO 22241‑4 - Refilling interface for the NOx reduction agent AUS 32 for?
ISO 22241‑4 on NOx reduction agent AUS 32 is useful for:
- Road vehicle engineers and manufacturers
- Manufacturers of diesel engines
- Manufacturers and suppliers of fluid equipment components
- Fuel industry
- Personnel of the laboratory to test NOx reduction agent
Why should you use ISO 22241‑4 - Refilling interface for the NOx reduction agent AUS 32?
A refilling system is a system of off-board system and on-board system, including their refilling interface, for dispensing AUS 32 into the on-board tank of the vehicle.
ISO 22241‑4 provides the functional requirements of the on-board refilling system and the off-board refilling system for AUS 32.
ISO 22241‑4 navigates you through the dimensional details, geometric location and orientation of the filler neck to accommodate an open refilling system.
The internal diameter and design of the inlet adapter are specified in ISO 22241‑4 to fit inside the filler neck.
The marking and colouring of the filler cap are mentioned in ISO 22241‑4.
ISO 22241‑4 provides the position of nozzle spout with magnet switch inserted into inlet adapter and the minimum free space required for refilling.
Overall, ISO 22241‑4 guides you on the refilling interface of AUS 32 in road vehicle diesel engines to enhance the environment in order to protect the health, sustain a healthy economy, and contribute to a vibrant economy.
What’s changed since the last update?
BS ISO 22241‑4:2019 supersedes BS ISO 22241‑4:2009. BS ISO 22241‑4:2019 includes some technical changes with respect to BS ISO 22241‑4:2009. These include:
- The definition of AUS 32 has been deleted as it is included in ISO 22241-1 and the document is cited normatively
- New definitions have been added
- The status of Annex A has been changed to normative and the Annex has been revised accordingly

