Quality inspection: checking your goods against the spec before they ship

What an inspection checks

The WTO's agreement on preshipment inspection describes the activity as the verification of the quality, the quantity, the price^[2] of goods, among other things, and says inspections should follow the standards defined by the seller and the buyer in the purchase agreement^[2]. Where the purchase agreement sets no standard, the WTO agreement says relevant international standards apply. It covers inspections that governments contract for or mandate, but the lesson carries over to the ones you book: whatever your order leaves out, the inspector can only judge against general standards, so write every requirement that matters into the order.

A typical pre-shipment check covers:

• quantity finished and packed against the order;
• workmanship and visible defects;
• measurements against your spec sheet or tech pack;
• colour and material against the approved sample;
• function and safety checks the product needs, such as zips, closures or seals;
• labels, barcodes, carton marks and packing.

Sampling and AQL

Checking every unit of a large order is slow and costly, so a pre-shipment inspection uses acceptance sampling, which ASQ defines as inspection of a sample from a lot to decide whether to accept that lot^[3]. The international standard ISO 2859-1 defines a system of acceptance sampling plans for inspection by attributes^[4]. The American standard ANSI/ASQ Z1.4 covers the same ground and provides tightened, normal, and reduced plans^[5], with switching rules that move between them as a supplier's results change over a run of lots.

Both are indexed by the acceptance quality limit, or AQL, which ASQ defines as the limit of a satisfactory process average^[3]. In practice you choose an AQL for each class of defect, the plan gives a sample size and the number of defective units allowed, and the lot passes or fails on the count. Set a lower, stricter AQL for defects that make a product unsafe or unusable than for cosmetic flaws.

When to inspect an overseas order

• Before production: check materials and components against the spec, when a wrong fabric or part is still cheap to replace.
• During production: check the first finished units, so a systematic fault is caught while most of the order is unmade.
• Before shipment: check a sample of the finished, packed order. If you book only one inspection, book this one, and time it before you pay the balance.
• At loading: confirm the right goods and quantity go into the container.

An inspection is not a lab test

A visual and measurement check at the factory does not replace laboratory testing where the law requires it. For children's products sold in the US, federal law requires testing by a third-party, CPSC-accepted laboratory^[6], and on passing results the responsible firm must issue a Children's Product Certificate (CPC)^[6]. Plan that testing alongside the inspection; one cannot stand in for the other.

Example: reading an AQL result

A pre-shipment inspection on one order

Line	Value
Order size	5,000 units
Sample size under the chosen plan	200 units
Major defects allowed at the chosen AQL	10
Major defects found	12
Result	Lot fails
Inspection cost	$330
Inspection cost per unit	$0.07

Illustrative figures, not a quote. Real prices depend on the spec, quantity and factory.

A failed lot is a negotiating position, not the end of the order. Ask for the goods to be sorted and reworked, then re-inspected at the supplier's cost, before you release the balance payment. An inspection checks one order; a factory audit checks the supplier behind it.