AQL

AQL is the Acceptable Quality Limit — the number of defects a lot may contain in the sample and still be judged acceptable, under a named sampling plan. It is a statistical rule, and that word carries most of the meaning.

The single most common misreading

AQL is not a quality claim. It is a sampling decision.

An AQL of 2.5 does not mean "2.5% acceptable quality". It means: draw a sample of this size from a lot of this size, count the defects, and apply this table to accept or reject the lot. Two things follow:

• A lot that passes AQL 2.5 can still contain defects in the bulk. The limit is set where accepting it is a reasonable business risk, not where the cloth is defect-free.
• A lot that fails does not mean the mill made bad fabric. It can fail on sampling chance alone, which is exactly why the plan is agreed in advance rather than after the goods arrive.

The accept/reject table

Quality is measured in defects per hundred units. For defects-per-unit inspection, the usual limits are:

Which number applies is decided per characteristic. A mill will typically quote a tight AQL for colour or width and a looser one for a minor cosmetic point — and a single "our AQL is 2.5" line on a spec sheet is not a real specification.

Three inputs, and all three must be named

1. Lot size — how many pieces are in the shipment. This sets the sample size code, and a lot-size figure is the first thing to agree, because everything else follows from it.
2. Inspection level — I, II or III. Level II is the default, and most people never say it out loud. Level III pulls a larger sample and is worth paying for on a first production run and not on a repeat.
3. AQL per characteristic — see above.

Name all three, or the number is decoration.

What belongs on the purchase order

Four lines, and each one prevents a specific argument later:

1. Lot size and how a lot is defined (per colour? per design? per roll count?)
2. Inspection level — state II explicitly rather than leaving it implied
3. AQL for each characteristic — critical / major / minor, not one global figure
4. The disposition rule — what happens on a reject: 100% inspection, re-sort and re-inspect at a tightened level, or concession against a claim. "Accept on reject" (re-inspecting until it passes) must be agreed explicitly, because it moves who pays for the sorting.

Where AQL does not reach

AQL samples. It says nothing about the parts it did not look at. Two consequences worth stating:

• It is not a substitute for approving a standard sample first. AQL governs shipment inspection against an agreed standard; without a sealed, signed reference sample the number has nothing to measure against. See Lab Dip for the approval step that comes before it.
• Four-point inspection is a different axis. A fabric can be free of weaving faults and still miss its specified width. See Four-Point System. The same logic applies to abrasion: a lot can pass AQL and still fail a stated abrasion resistance requirement on one characteristic.
• AQL measures no property at all — it counts defects. Which defects you count is the entire specification: light fastness, abrasion, width, shade. Each of those has its own page, and each carries its own instrument and its own scale: light fastness, abrasion resistance.

Where we stand

We do not publish a single house AQL, because publishing one would be a claim we could not keep: the right number depends on the characteristic, the lot size and the end use. It is agreed per order, in writing, before goods are made — and the inspection level, critical/major/minor split and reject disposition all travel with it.