AQL inspection in China: a practical guide
How sampling inspection works, what critical, major and minor defects mean, and what AQL cannot tell you about a production run.
By the Neofulfill team in Shenzhen — we source, inspect and ship the goods these guides cover.
7 min read
In this article8 sections
Open a factory inspection report and you will probably see the letters AQL. Do not let the table of numbers do all the reassuring. Once you know what those numbers mean, you can tell what was checked, what was missed and why the batch passed.
What AQL is
AQL stands for Acceptable Quality Limit. The best-known sampling standard behind it is ISO 2859. It answers two practical questions: how many units should the inspector open, and how many defects can that sample contain before the lot fails?
AQL does not decide whether your product is good. It is only a way to choose and judge a sample. You still have to define the product, the checks and what counts as a defect.
Why brands use sampling rather than checking everything
Checking every piece in a large run takes time and money. For many products it is unnecessary. A sample gives the inspector enough evidence to make a decision before the shipping date.
There is still risk. A sampled unit may be fine while an unopened unit is not. The difference is that the plan measures that risk. Opening a few easy cartons at random does not.
Critical, major and minor defects
Not every fault deserves the same response. A sharp edge is not equal to a slightly crooked label. Before inspection, the buyer sorts possible faults into three classes.
| Class | What it means | Typical tolerance |
|---|---|---|
| Critical | Could be unsafe for the user, or breach a regulation in the destination market | Normally zero |
| Major | Would likely cause a return, a complaint or a product that does not function as described | Low |
| Minor | A deviation from specification a customer would probably accept | Higher |
The buyer and supplier agree the tolerance for each class. Context matters. A small scuff on a shipping carton is one thing; the same mark across the front of a gift box is another. A standard cannot make that commercial call for you.
Inspection levels and what they change
The general inspection levels are I, II and III. Level II is the usual starting point. Level I gives a smaller sample. Level III gives a larger one.
A larger sample takes longer, but it is more likely to uncover an occasional fault. We may use that extra scrutiny with a new factory, after a bad run or when a customer-facing defect would be especially costly.
How sample size is decided
Start with the production quantity and the chosen inspection level. The standard turns those two inputs into a sample-size code. Combine that code with the AQL figure and you get an acceptance number and a rejection number.
Then the inspector opens the sample and counts faults by class. A count at or below the acceptance number passes. A count that reaches the rejection number fails. The sample does grow for a larger order, just not piece for piece.
We set the inspection level and defect tolerances for each project. A single house rule would ignore the product, the destination market and the agreement with the supplier.
Pre-shipment inspection, and when to do it
A pre-shipment inspection takes place near the end of production, when the goods are finished and packed or nearly packed. This is the last sensible chance to catch a problem before the batch becomes overseas inventory.
Too early, and there is not enough finished stock to judge. Too late, and the goods are already moving. We also want enough time left for the factory to sort, repair or remake something if the check fails.
Our inspector does more than count defects. The report should confirm quantity, packaging, labels and the match against the approved sample. Quality control and production follow-up explains how those checks continue during the run.
What AQL cannot do
A pass has limits. Keep these five in mind when you read the report.
- Some units stay closed. A passed sample does not make every piece perfect.
- The written specification still rules. If no colour range was agreed, the inspector has no line to judge it against.
- A quick check is not a lifetime test. The report cannot show how an item will behave after months of use.
- Inspection cannot repair a weak supplier. Repeated failures call for a sourcing decision.
- The next run starts again. One good batch does not guarantee another.
Where QC sits in sourcing
Inspection is one checkpoint. The work starts earlier with a clear specification and an approved sample. Production follow-up matters too, because a problem is easier to fix while the factory is still making the batch.
That is why we keep supplier selection, follow-up and inspection connected. If the report finds a problem, the same team can take it back to the factory and push for a correction. Our China sourcing page shows how those stages fit together.
Common questions
What AQL level should I use?
Does a passed inspection mean there are no defects?
Can inspection happen before I pay the supplier?
Is AQL relevant for small orders?
Need product checked before it ships?
Tell us what the product is, who is making it and where you sell it. We’ll map the checks and documents the order needs.