LAF · Calibration procedure
Non-viable particle count
Counts airborne particles of ≥0.5 µm and ≥5.0 µm at defined locations in the work zone with a calibrated particle counter, to classify the unit as ISO 5 / Grade A.
PURPOSE
Why this is checked
Particle counts show that the air in the work zone is as clean as Grade A requires. They confirm the combined performance of the filter, the seal and the airflow pattern.
Frequency
Typically every 6 months (some sites test HEPA integrity annually), and after filter replacement, relocation or major repair, as defined in your SOP.
Learn how the LAF worksYOU WILL NEED
Standards & tools
- Calibrated discrete airborne particle counter (e.g. 28.3 L/min) with isokinetic probe, calibrated as per ISO 21501-4
BEFORE YOU START
Prerequisites
- Air velocity and HEPA integrity tests passed
- Unit running for at least the stabilisation time; work zone clean and empty for 'at rest' testing
- Number of sampling locations and sample volume calculated as per ISO 14644-1 and your SOP
PROCEDURE
Step by step
- 1Place the isokinetic probe at working height, facing into the airflow, at each location.
- 2Sample at least the minimum volume required at each location (sites commonly take 1 m³ for Grade A classification, or as per your SOP).
- 3Record counts for ≥0.5 µm and ≥5.0 µm and convert them to particles per m³.
- 4Repeat in operation (with a simulated activity) if the SOP requires 'in operation' classification.
- 5Compare each location with the limits.
RECORD
Example observation table
| Location | Volume sampled (L) | Count ≥0.5 µm | ≥0.5 µm per m³ | ≥5.0 µm per m³ |
|---|---|---|---|---|
| L1 (left) | 28.3 | 6 | 212 | 0 |
| L2 (centre) | 28.3 | 4 | 141 | 0 |
| L3 (right) | 28.3 | 9 | 318 | 0 |
CALCULATION
How to calculate the result
Particles per m³ = Count ÷ Volume sampled (m³) (1 m³ = 1000 L)
- Location L3: 9 particles ≥0.5 µm in 28.3 L = 0.0283 m³
- Concentration = 9 ÷ 0.0283 = 318 particles/m³
- Limit for ISO 5 / Grade A at ≥0.5 µm is 3,520 /m³: Pass
ACCEPTANCE CRITERIA
Pass if
- ≥0.5 µm: not more than 3,520 particles/m³ at every location (ISO 5 / Grade A, at rest and in operation).
- ≥5.0 µm: in line with Annex 1 expectations for Grade A (no limit for ISO classification; Annex 1 gives 29 /m³ in operation), as defined in your SOP.
IF IT FAILS
What to do
- Check the counter calibration, probe position and sampling technique, then repeat the count.
- Clean the unit and check velocity and HEPA integrity.
- Investigate room conditions and operator activity for 'in operation' failures.
- Do not use the unit for aseptic work until it passes.
MORE
Other LAF calibrations
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.