What AQL Is and How It's Used to Inspect Clothing

Short answer: AQL (Acceptable Quality Level) is a standard sampling method to decide whether a production lot is accepted or rejected. Based on lot size, a table from the ISO 2859-1 standard says how many garments are inspected and the maximum number of defects allowed in that sample. In apparel it's common to use zero tolerance for critical defects, AQL 2.5 for major defects and AQL 4.0 for minor defects, although the level is agreed with each manufacturer before production.

Checking a thousand-unit run garment by garment is slow, expensive and, oddly enough, doesn't guarantee better quality: inspectors get tired and start letting defects through. AQL solves that with statistics. Instead of checking everything, a randomly chosen sample is checked and the decision follows a rule both parties know in advance.

How AQL works

The process has three steps:

• Lot size. Count the units in the production being inspected.
• Sample size. With the lot size and the inspection level, the standard's table gives a code letter, and that letter tells you how many garments to inspect.
• Acceptance limits. For each AQL level, the table gives the maximum number of defects accepted (Ac) and the number at which the lot is rejected (Re).

If the sample has as many defects as the acceptance number or fewer, the lot passes. If it has as many as the rejection number or more, the lot fails.

How many garments are inspected per lot

With general inspection level II, the most used in apparel, ISO 2859-1 sets these sample sizes:

• - Lot of 26 to 50 units: 8 garments inspected.
• - Lot of 51 to 90 units: 13 garments inspected.
• - Lot of 91 to 150 units: 20 garments inspected.
• - Lot of 151 to 280 units: 32 garments inspected.
• - Lot of 281 to 500 units: 50 garments inspected.
• - Lot of 501 to 1,200 units: 80 garments inspected.
• - Lot of 1,201 to 3,200 units: 125 garments inspected.

Notice something important: the sample doesn't grow in proportion to the lot. A small lot has a much larger share of its garments inspected than a large one.

What AQL 2.5 and AQL 4.0 mean

The AQL number isn't the percentage of bad garments you'll receive. It's the quality level the sampling plan considers acceptable as a process average. In practice it becomes a maximum number of defects allowed in the sample. Some examples from the single sampling, normal inspection table:

• - Lot of 151 to 280 units (sample of 32): at AQL 2.5 up to 2 defects are accepted and it's rejected at 3; at AQL 4.0 up to 3 are accepted and it's rejected at 4.
• - Lot of 281 to 500 units (sample of 50): at AQL 2.5 up to 3 accepted, rejected at 4; at AQL 4.0 up to 5 accepted, rejected at 6.
• - Lot of 501 to 1,200 units (sample of 80): at AQL 2.5 up to 5 accepted, rejected at 6; at AQL 4.0 up to 7 accepted, rejected at 8.
• - Lot of 1,201 to 3,200 units (sample of 125): at AQL 2.5 up to 7 accepted, rejected at 8; at AQL 4.0 up to 10 accepted, rejected at 11.

For critical defects, the ones that make a garment unsafe, the norm is to accept none.

Critical, major and minor defects

AQL is applied separately to each defect type, which is why classifying them well is essential:

• - Critical: puts the wearer at risk or makes the garment unsellable. A needle or metal object inside the garment, a sharp edge.
• - Major: the end customer notices and will likely return the garment. An open seam, an out-of-tolerance measurement, a visible stain.
• - Minor: an imperfection that doesn't affect use or sale. An untrimmed thread, an irregular stitch in a hidden area.

What AQL doesn't do

AQL is a decision tool, not a manufacturing tool. Three things are worth being clear about:

• - It doesn't improve bad production. It only says whether a lot passes. Quality is built earlier: in the fabric, the pattern, the sample and in-line control during sewing.
• - It doesn't replace the approved sample. To know whether something is a defect, there must be a standard to compare against. That standard is the approved sample and its tech pack.
• - It's useless if not agreed in advance. The AQL level, defect classification and who inspects are defined before production. Arguing about it once the lot has arrived is too late.

What to agree with your manufacturer

Before confirming production, ask and put in writing:

• The reference standard: the approved sample and its tech pack.
• The inspection level and AQL for critical, major and minor defects.
• What counts as critical, major and minor for your garment type.
• Whether there's in-line control during sewing or only final inspection.
• What happens to garments that don't pass.

How we do it at The Full Package

At The Full Package S.A.S there is one standard: the sample the brand approved. Every sample is checked against thirteen points and needs two sign-offs, quality and the pattern maker, to move into production. During sewing there's inspection at every workstation, and on the finished lot we run the final sampling inspection under AQL criteria. The inspection level and limits are defined with each brand for its project and we review them directly in a meeting.

Conclusion

AQL turns the question "is this production right?" into an objective rule both parties know from the start. But it only works on a foundation: an approved sample, well-classified defects and control before the final inspection.

Want to know what quality control would look like for your collection? Write to commercial@thefullpackage.com.co or WhatsApp +57 311 546 2347.