How AQL sampling works on a real chair order
AQL appears on every quotation and is understood by almost nobody. It is a sampling plan, not a promise, and the number you agree decides how many faulty chairs you have already paid for.
Published by JPChairs · Chair manufacturer in Foshan, China · 2026-10-14
What AQL does and does not tell you
AQL — acceptable quality limit — is a statistical sampling plan drawn from ISO 2859-1, the same tables published as ANSI/ASQ Z1.4. It answers one narrow question: on the evidence of this random sample, is the whole lot likely to sit at or below the defect rate we agreed?
Three inputs set the plan. Lot size produces a code letter. Inspection level is almost always General Inspection Level II for furniture. The AQL number is the defect rate you tolerate, expressed as a percentage.
What AQL does not tell you is whether the chair is well engineered. A lot can pass at 2.5 and still loosen after six months because the joint design is weak. Sampling measures consistency, not design.
Sample sizes for real order quantities
At General Inspection Level II, single sampling, normal inspection:
- 51 to 90 chairs — code E, 13 pieces pulled. At AQL 2.5, accept on 1 defect, reject on 2.
- 91 to 150 — code F, 20 pieces. AQL 2.5: accept 1, reject 2.
- 151 to 280 — code G, 32 pieces. AQL 2.5: accept 2, reject 3.
- 281 to 500 — code H, 50 pieces. AQL 2.5: accept 3, reject 4.
- 501 to 1200 — code J, 80 pieces. AQL 2.5: accept 5, reject 6.
- 1201 to 3200 — code K, 125 pieces. AQL 2.5: accept 7, reject 8.
So a 500-chair order is judged on 50 chairs. A plan that accepts 3 defects out of 50 is not a plan that delivers a clean container, which is why the number matters more than the word "inspected" on the quotation.
Tightening to AQL 1.0 on that same 50-piece sample drops the accept number to 1 and reject to 2, at no extra inspection time.
Critical, major, minor
Defects are graded, and each grade carries its own AQL:
- Critical, AQL 0 — anything that can injure or makes the chair unusable: a structural failure at a load-bearing joint, a sharp burr on a tube end or weld, a missing leg bolt, a lift mechanism that will not hold. One critical defect fails the lot regardless of the accept number.
- Major, AQL 2.5 — what a guest or your own team would reject on sight: wobble over 1.5 mm, a scratch longer than 10 mm visible at 1 m, seam misalignment over 3 mm, colour drift beyond the agreed tolerance, foam already compressed more than 5 mm.
- Minor, AQL 4.0 — cosmetic and unlikely to be noticed in service: a glue line under 2 mm, a blemish on an unexposed face, a carton print smudge.
Writing the grading into the contract matters more than the AQL number itself. "AQL 2.5" with no definitions is an argument waiting for a container to arrive. The ranges we ship against, with the specifications each one is built to, are listed in the restaurant chair specifications.
Tolerances worth writing down
These six lines remove most of the subjectivity from a final inspection:
- Overall dimensions — plus or minus 5 mm; seat height plus or minus 3 mm, because tables are fixed and guests are not.
- Wobble — three legs on a level surface plate, gap under the fourth no more than 1.0 mm.
- Colour — Delta E 1.5 or less within one batch, 2.0 or less against the approved reference sample, read on a flat face at a fixed angle.
- Foam and upholstery — thickness plus or minus 2 mm, density within 5 per cent of the specified kg/m³.
- Hardware — every fastener present, torqued to one setting, no mixed head types on a single chair.
- Finish — cross-hatch adhesion at 2 mm spacing with no loss beyond grade 1.
The sealed reference sample is the anchor. Keep one at the factory and one with you; every dispute resolves against it.
Who inspects, and when
Three checkpoints are worth the fee:
- Pre-production — before the line starts, while a drawing or material change still costs nothing.
- During production — at 20 to 30 per cent complete. This is the one that actually fixes problems, because there are still days left to change course.
- Final random inspection — at 80 to 100 per cent packed. Book it 5 to 7 working days ahead; an inspector covers 300 to 500 chairs in a man-day depending on how much measuring is involved.
Final inspection alone is the weakest option. It tells you the container is bad at the exact point where the only remaining remedy is rework in your own warehouse.
When a lot fails
Three outcomes, in order of cost. The factory reworks the lot and reinspects, which adds 3 to 10 days. Or the lot is sorted 100 per cent and only sound units ship, adding 1 to 3 days plus sorting labour. Or you accept it against a credit note — the option to avoid where a structural fault is involved.
Agree in advance who pays the second inspection fee: normally the factory on a clear failure, the buyer on a borderline result. Also state whether reinspection runs at normal or tightened inspection. After one rejection the standard plan moves to tightened automatically, which raises the sample size and lowers the accept number.
To see how frames are built and checked before they are packed, start with the factory production lines; the shipping questions that follow inspection are answered on the shipping FAQ.
