The scope of this document focuses on the setup and use of solid particle number (SPN) counting devices in both engine development and certification environments. The document reviews best practices for collecting and measuring samples from both raw and diluted exhaust gas streams across several sample probe insertion locations relative to installed aftertreatment devices. Appropriate dilution techniques, sample transfer processes, and temperature management techniques are included. Finally, performance and validation checks are covered to ensure that long-term degradation and instrument failures can be identified quickly.

The particle size range targeted in this document is >23 nm, which aligns with the present EU SPN regulations and targets only solid particles. Current commonly available measurement devices are designed for counting efficiencies of 50% at 23 nm and 90% counting efficiencies at 40 nm so the contents of this document primarily address these particle sizes. It is expected that future regulations will target a lower 10 nm size cut-point. Consequently, a short section has been added discussing best practices that a user may need to consider when measuring particles in this size range.