What is CFU?
Colony Forming Unit: a measure of viable bacterial or fungal numbers used in microbial monitoring. Action levels vary by ISO classification zone.
Viable air and surface samples are incubated and read as CFU counts; the allowable level depends on where the sample was collected — the cleaner the zone, the lower the threshold. Any recovery in an ISO 5 primary engineering control deserves scrutiny, while higher counts may be acceptable in an ISO 8 ante room.
Trending matters as much as single results: a slow rise in CFU counts at one sample point often signals a cleaning, garbing, or airflow problem before any single sample exceeds its action level. Exceedances should trigger identification of the organism and a documented investigation.
See how CompliRx handles this in practice:
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