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.