TERM-PARTICLE-COUNT
Particle Count
Fluid Cleanliness
Also: particle concentration · particle contamination level · particle density
Abbrev: p/mL · p/100mL
Canonical Definition
The number of particles of a specified size range present in a unit volume of fluid, typically expressed as particles per millilitre (p/mL) or particles per 100 mL. Particle counts are measured by automatic particle counters using laser light obscuration or light scattering, calibrated per ISO 11171 using NIST-traceable calibration standards. Results are reported as cumulative counts at threshold sizes of ≥4 µm(c), ≥6 µm(c), and ≥14 µm(c) for ISO 4406 cleanliness code determination.
Engineering Context
Particle counting is the fundamental measurement underlying all fluid cleanliness standards. Field particle counting uses portable laser particle counters inserted into sampling ports on operating machinery. Laboratory particle counting uses dedicated optical benchtop instruments. Sample handling — avoiding contamination from bottles, tubing, and ambient environment — is critical for accurate results.
Protection Systems
Knowledge Center Articles
KC-00 Governance Metadata
| Permanent ID | TERM-PARTICLE-COUNT |
| Category | Fluid Cleanliness |
| Status | Published |
| Version | 1.0 |
| Last Reviewed | 2026-07-05 |