The short answer
AQL stands for acceptable quality limit. In a pre-shipment inspection, an inspector draws a random sample from the finished lot, checks each sampled unit, counts the defects by class, and compares the count with accept and reject numbers from a sampling plan. The plans usually come from ISO 2859-1, an international standard for sampling inspection by attributes. The standard ties sample size to lot size and to an inspection level, and it ties the accept number to the AQL chosen for each defect class. Levels and limits are agreed per order between buyer and supplier, so this note explains the concept rather than quoting a single set of numbers that applies to everyone.
How sampling works in plain terms
The logic is simple. The larger the lot, the larger the sample, but not in proportion. The standard has tables that convert lot size into a sample size letter and then into a sample size. A tighter AQL means fewer defects are allowed. A general inspection level controls how big the sample is for a given lot: a higher level inspects more units. The result is a decision rule: if the number of defective units in the sample is at or below the accept number, the lot passes; if it is at or above the reject number, it fails. Sampling reduces risk but does not remove it, so a passing lot can still hold some defects. That is why AQL is paired with process controls earlier in the route, such as those in how dash cams are made.
Defect classes
Inspectors do not treat all defects the same. A standard practice splits them into three classes, and buyers set a different limit for each.
| Class | Meaning | Dash cam examples |
|---|---|---|
| Critical | Unsafe or against regulation | Overheating in test, exposed live parts, missing required marking |
| Major | Product fails to work or is unsellable | No recording, GPS never locks, WiFi will not pair, blurry image, missing accessory |
| Minor | Cosmetic or slight, still usable | Scratches on shell, small print flaw on box, loose cable tie |
Critical defects are usually set to zero tolerance. Majors get a tighter limit than minors. The values are chosen per order and written into the inspection brief; do not accept an unstated default.
What an inspector checks on dash cams
- Quantity and carton marking: count against the order, carton marks, labels, barcodes.
- Packaging: box print, inserts, manuals in the right language, accessories complete.
- Appearance: shell, screen, lens window, buttons, mount fit.
- Function: power on, record, playback, G-sensor lock, GPS and WiFi if fitted. See functional testing.
- Image check: a short clip against a chart or scene to catch bad focus. See lens focus calibration.
- Firmware: version string against the approved sample.
- Markings: model, regulatory marks and country information where they apply.
Who inspects
Inspection can be done by the factory's own quality staff, by the sourcing desk, or by an independent third-party inspection company that the buyer appoints. A factory's own inspection is part of the normal process but is not independent. Desk checks add a second pair of eyes before shipment. A third-party inspection is optional and adds an outside report; it makes the most sense for a first order with a new factory, a large order, or a program where the end customer expects a formal report. Costs and scheduling for each option are quoted per program.
Setting the plan for your order
- Agree the standard and level before production. State ISO 2859-1, the inspection level and the AQL for each defect class in the purchase terms.
- Attach a defect list. Describe what counts as a critical, major or minor defect for this product, with photos where possible.
- Fix the golden sample. Keep an approved sample sealed on both sides as the reference for look and function.
- State what happens on a fail. Rework and re-inspect, partial acceptance or rejection; write down who pays for what.
- Time the inspection. Inspect when the lot is fully produced and mostly packed, before final shipment booking.
Interpreting an inspection report
A useful report is more than a pass or fail stamp. It should state the lot size, the sample size drawn, the standard and level used, the AQL per defect class, and the defects found, each with a photo and a location in the carton. From those numbers a buyer can see not only whether the lot passed but how close it came: a lot that passed with the accept number minus one is a different signal from one that passed cleanly, and it suggests looking harder at the next lot. Photos matter because they turn a word like "scratch" into something specific that the factory can trace to a station. Patterns in the report are information too. If several sampled units show the same fault, the true rate in the lot is probably higher than the sample suggests, and a conversation with the factory should start before shipment rather than after arrival. Ask the desk to walk through the report with you the first time; after two or three orders, reading it takes minutes.
Limits of AQL
AQL is a tool for lot decisions, not a promise about every unit. A small sample can miss a defect that affects a few percent of units. It also does not test long-term behavior such as lens drift, heat aging or card wear, which are handled by burn-in and temperature sampling. And a lot can pass on count but still contain a pattern that matters, for example every unit in one carton coming from a bad solder batch. A good inspector notes patterns as well as counts. For the reasoning behind rates, read defect rates and what a buyer can control.
How the desk uses it
The sourcing desk agrees an inspection brief with the buyer, coordinates the sampling at the partner factory, and returns the report with photos before shipment is released. Test reports and certificates come from the producing factory or lab and are verified by report number; see reading test reports. The inspection steps are listed on the quality control page. To set up a plan for your order, include your preferred level and defect list in the quote request.