If you book a pre-shipment inspection in China, the inspector will usually ask which AQL you want. Many buyers just accept "2.5 major, 4.0 minor" without knowing what it means. It is worth five minutes to understand, because it decides how many units are checked and how many defects you are agreeing to accept.
What AQL means
AQL stands for acceptance quality limit. It comes from a sampling standard, ISO 2859-1 (closely related to the older ANSI/ASQ Z1.4 and MIL-STD-105). Instead of checking every unit, the inspector checks a random sample, and the AQL decides how many defective units can be found in that sample before the lot fails.
A lower AQL number is stricter. AQL 1.0 accepts fewer defects than AQL 2.5, which accepts fewer than AQL 4.0.
The three inputs
Lot size: how many units are in the shipment being inspected.
Inspection level: usually General Level II for normal inspections. Level I checks fewer units, Level III more. Special levels are used for expensive or destructive tests.
AQL for each defect class: commonly critical, major and minor defects get different limits.
The lot size and inspection level give a sample size code letter, which gives the sample size. The AQL then gives the accept and reject numbers for that sample.
An example
For a lot of 5,000 units at General Level II, the standard gives a sample size of 200 units. With a common set of limits:
| Defect class | AQL | Accept if defects found are at most | Reject if defects found are at least |
|---|---|---|---|
| Critical | 0 (not accepted) | 0 | 1 |
| Major | 2.5 | 10 | 11 |
| Minor | 4.0 | 14 | 15 |
So if the inspector finds 9 major defects in the 200 units, the lot passes on majors. If they find 11, it fails. Always check the numbers against the standard tables for your own lot size and levels; the inspector should show them in the report.
Critical, major and minor defects
Critical: a defect that could cause injury or breaks a legal requirement, such as an exposed live part or a sharp edge on a toy. Most buyers accept zero.
Major: a defect that makes the product fail or that a customer would likely return it for, such as a function that does not work or a wrong dimension that affects use.
Minor: a defect that does not affect use but falls short of the standard, such as a small scratch or a slightly uneven stitch.
The most important work happens before the inspection: write a defect list for your product that says which problems are critical, major and minor. Without it, the inspector has to guess.
Choosing your AQL
Common consumer goods: often 0 critical, 2.5 major, 4.0 minor.
Higher-value or safety-sensitive products: stricter, such as 1.5 or 1.0 major.
Low-value promotional items: some buyers accept looser minor limits.
AQL fits products made in quantity. For a single machine or a small number of large units, such as excavators or crushers, sampling makes no sense: every unit is checked against the specification and run, as described in the Xuzhou machinery guide.
What else a pre-shipment inspection checks
Besides the defect count, a pre-shipment inspection normally checks quantity, packing and markings, product specifications and dimensions against the approved sample, function tests, and any special tests you have agreed, such as a drop test for cartons or a material check. The inspection is usually done when at least 80% of the goods are finished and packed.
If the lot fails
A failed inspection is not the end of the order. Usually the supplier sorts or reworks the goods and a re-inspection is done. Agree in the contract who pays for re-inspection, and do not pay the balance until the re-inspection passes.
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LocalAuditChina is an independent verification service, not a certification body. Reports are findings to support your purchasing decision.
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