AQL (Acceptable Quality Limit)
A sampling standard that sets how many units to inspect and how many defects are acceptable before a batch is rejected.
TL;DR: AQL is a statistical method for inspecting a sample instead of every unit. It tells the inspector how many units to check and the maximum number of defects allowed for the batch to pass.
AQL sampling is based on ISO 2859-1 and similar national standards such as ANSI/ASQ Z1.4. The inspector starts with the lot size and an inspection level. General inspection level II is the most common default. The tables then give a sample size and, for each AQL value, the acceptance and rejection numbers.
Defects are usually sorted into three classes, each with its own AQL value. Typical settings are zero tolerance for critical defects, which could cause harm or break legal rules, 2.5 for major defects, which affect use or saleability, and 4.0 for minor defects, which are small cosmetic issues. These are common choices, not requirements. Buyers can set stricter or looser values depending on the product and market.
A lower AQL number means a stricter standard. For example, AQL 1.0 allows fewer defects than AQL 4.0 for the same sample size.
AQL settings and defect definitions should be agreed with the supplier before production, not first raised at inspection. Write down what counts as critical, major, and minor for your product. For glass mosaic, examples might be cracked tiles, wrong colors against the approved sample, sheets out of layout order, or poor backing adhesion. See PSI (Pre-Shipment Inspection) and Third-Party Inspection.