Calculator
Formula used
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Cn = 10^N × (0.1 / D)^2.08
Cn is the maximum permitted concentration (particles/m3), N is ISO class, D is particle size (µm). -
NL from Table A.1 for areas ≤ 1000 m2, otherwise NL = ceil(27 × A / 1000)
A is floor area in m2. NL is the minimum number of sampling locations. -
Vs = (20 / Cn) × 1000 litres
Minimum single sample volume per location, sized to detect at least 20 particles at the class limit.
How to use this calculator
- Select the unit system and enter room dimensions.
- Choose the particle size used for acceptance criteria.
- Enter your target ISO class for the space.
- Provide measured concentration, or sample count plus volume.
- Enter your counter flow rate and your minimum sample time.
- Press Submit to see PASS/FAIL, limits, and sampling plan.
- Use Download CSV or PDF to share the report.
Example data table
| Scenario | Target ISO | Size (µm) | Measured (particles/m3) | Expected result |
|---|---|---|---|---|
| Filling suite check | 5.0 | 0.5 | 1,500 | PASS (limit ≈ 3,520) |
| Gowning room trend | 7.0 | 0.5 | 400,000 | FAIL (limit ≈ 352,000) |
| Corridor baseline | 8.0 | 0.5 | 950,000 | PASS (limit ≈ 3,520,000) |
Examples are illustrative; always follow your project’s qualification protocol.
Cleanroom classification in construction turnover
During pharmaceutical build-outs, particle classification becomes a practical acceptance gate for areas such as corridors, gowning, and process suites. This calculator converts your selected ISO class and particle size into a maximum permitted concentration, then compares it to measured results for a clear PASS/FAIL statement.
Room area drives minimum sampling locations
Qualification planning is not only about limits; it also depends on coverage. Floor area is used to determine the minimum number of sampling locations, supporting consistent spatial confidence when commissioning contractors hand over to validation and operations teams.
Sampling volume and time sizing
To avoid under-sampling, the tool estimates the minimum sample volume per location and translates that volume into time using your counter’s flow rate. When your SOP enforces a minimum duration, the calculator applies the larger of the calculated time and your specified minimum.
Interpreting trends and rework risk
Beyond a single test, trending concentrations helps isolate sources such as incomplete cleaning, poor gowning practices, or unbalanced airflows. Use repeated measurements at identical locations to quantify improvement after corrective actions, and document objective evidence for closeout packages.
Example data for documentation packages
The following examples illustrate how raw counts can be converted to concentrations for reporting:
- Count: 420 particles, Volume: 28.3 L ⇒ 14,841 particles/m3 (at 0.5 µm)
- Count: 65 particles, Volume: 56.6 L ⇒ 1,148 particles/m3 (at 0.5 µm)
- Count: 1,900 particles, Volume: 28.3 L ⇒ 67,138 particles/m3 (at 0.5 µm)
Use consistent locations, flow rate, and particle size to keep comparisons meaningful.
FAQs
1) What does “PASS” mean in this report?
PASS means the measured concentration at the chosen particle size is less than or equal to the calculated ISO limit for the selected class. It does not replace your full protocol or environmental monitoring program.
2) Should I use 0.5 µm or 5.0 µm for acceptance?
Use the particle size required by your project specification, URS, or validation protocol. Many cleanroom classifications focus on 0.5 µm and 5.0 µm, but requirements vary by process and grade.
3) Why does the calculator ask for room dimensions?
Room dimensions provide floor area and volume for documentation and to estimate the minimum number of sampling locations. The acceptance limit is based on ISO class and particle size, not the room volume.
4) How is concentration calculated from sample count?
Concentration is computed as count divided by sampled volume in cubic meters. The tool converts litres to m3, then calculates particles/m3. Ensure your counter’s reported volume matches the run conditions.
5) What flow rate should I enter?
Enter the particle counter’s actual sampling flow rate in litres per minute. The calculator uses it to estimate time needed to collect the minimum sample volume per location and to compute the sampled litres for reporting.
6) Can I classify a room if results are worse than ISO 9?
If the measurement exceeds the ISO 9 limit at the selected particle size, the tool reports “Above ISO 9”. In practice, investigate housekeeping and airflow controls, then retest per your protocol.
7) Are the PDF and CSV suitable for regulated records?
They are useful for drafts, field notes, and turnover packs. For regulated records, follow your document control and data integrity procedures, include instrument calibration details, and maintain traceability to raw counter files.