A particle measurement turns “it looks clean” into a figure: the ISO class a room meets. Here is how such a measurement works and how to read the result.
Setting the sample points
ISO 14644-1 prescribes how many sample points are needed based on the room’s area. The points are spread representatively across the hall so a single clean or dirty spot does not skew the result.
Counting with the instrument
A calibrated particle counter draws a known volume of air at each point and counts particles by size class, typically from 0.5 µm up. The counter must be calibrated to classify reliably.
Comparing to the class limits
The measured concentrations are compared against the ISO 14644-1 limits. If the room stays below the Class 8 limit, it meets that class. If not, the pattern points to where the load climbs.
What it is not
A snapshot describes the state at that moment; continuous monitoring is something else. A measurement is most valuable at logical moments: at commissioning, after a deep clean, or to demonstrate a standard.
Key takeaways
- Sample points scale with the room area.
- A calibrated counter counts by size class.
- Concentrations are compared to ISO limits.
- It is a snapshot, not monitoring.