← Technology WikiAQL (Acceptable Quality Limit)
AQL is the statistical sampling standard (ISO 2859-1) that defines how many units to inspect and how many defects are acceptable — the common language of factory QC and third-party inspections.
How it works
- Based on lot size: larger lots get larger sample sizes per the standard tables.
- Defects are classified: critical (safety — usually AQL 0), major (function — often 1.0–2.5), minor (cosmetic — often 4.0).
- AQL 2.5 for major defects means: at that defect rate, most lots pass; it is NOT a guarantee of 2.5% defects.
- Used by SGS, TUV, and factory QC teams worldwide — if your inspector and factory don't share an AQL, you don't share a standard.
Key specifications
| Standard | ISO 2859-1 |
| Critical defects | Usually AQL 0 |
| Major defects | Often 1.0–2.5 |
| Minor defects | Often 4.0 |
What buyers and QC should check
- Put the AQL table IN the purchase contract — 'good quality' without an AQL is unenforceable.
- For water purifiers: define leak/pressure failures as critical or major, never minor.
- CWS works to buyer-specified AQL and shares per-batch inspection records.
Free one-page QC checklist (PDF)
The buyer checks from this entry, condensed for the factory floor or the inspection. No signup needed.
Download free PDF checklistCommon questions
What AQL should I require for water purifiers?
Common practice: critical defects AQL 0, major (functional/leak) 1.0–2.5, minor (cosmetic) 4.0. Put it in the contract.
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